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Runoff : urbanization & land use

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Title:
Runoff : urbanization & land use
Creator:
Goebel, John
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English

Thesis/Dissertation Information

Degree:
Master's ( Master of landscape architecture)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
College of Architecture and Planning, CU Denver
Degree Disciplines:
Landscape architecture
Committee Chair:
Young, Daniel B.

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Source Institution:
University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
Copyright John Goebel. Permission granted to University of Colorado Denver to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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Full Text


RUNOFF:
URBANIZATION & LAND USE
PART 1: RESEARCH

PREPARED
BY
JOHN GOEBEL

This thesis research is submitted as partial fulfillment of the requirements for a Master of Landscape Architecture Degree at the University of Colorado at Denver, College of Design & Planning, Graduate Programof Landscape Architecture.
Accepted:
Date


CONTENTS
PREFACE ii
1. INTRODUCTION
URBAN STORMWATER MANAGEMENT i
RESEARCH SCOPE § SCALE 5
PROJECT LOCATION 7
II. BACKGROUND
THE HYDROLOGIC CYCLE 9
HISTORIC PERSPECTIVE 13
URBAN RUNOFF 17
MANAGEMENT METHODS 28
THE SOCIAL SYSTEM 40
III. INTERPRETATION
IMPLICATIONS OF TRENDS $ PRACTICES 47
CONCLUSIONS 59
REFERENCES 69
APPENDICES
ISSUES TO LANDSCAPE ARCHITECTS 72
HYPOTHESIS 75
CASE STUDY, BUDGET, $ TIME LINE 76
THESIS COMMITTEE 77


PREFACE
MOVING TOWARD A HIGHER QUALITY OF LIFE
The specific purpose of this study is to assist communities in deriving additional benefits from their stormwater management systems. The method by which these additional benefits are to be gained is by proposing multiple purposes and uses for stormwater and the lands required for its management. These multiple purposes and uses will be based on the natural, social, and institutional conditions existing within and around the community seeking to upgrade their system. This study will be of value if the results enhance the services and opportunities a particular urban environment affords its residents (i.e. enhances the reasons why people reside in a particular community), and enhances these attributes in a manner that elevates the visual and aesthetic features of outdoor spaces in a practical and feasible way.
The general purpose of this study is to enhance the attributes of urban life and to elevate the visual and aesthetic features of urban life and to elevate the visual and aesthetic features of outdoor urban spaces by increasing the efficiency of the urban organism. The healthy urban organism, or community, is comprised of many elements all working in harmony to provide its residents with the services and lifestyle its residents desire. The residents, through democratic action, determine the services and the kind of lifestyle they want their community to provide and then adjust the various elements which make up the urban organism so that the organism will furnish the services and particular lifestyle desired by the majority based on natural, social, and economic limitations and opportunities. It follows then, that as residents of a community we are at once producers and consumers of our urban environment. As producers and consumers it is to
II


our benefit to make sure that we receive the maximum benefits from each working element of the urban organism. Each element of the organism must fulfill its potential efficiently and economically without adversely affecting the harmony of the total organism.
Stormwater management is an element of the urban organism which, in many communities, has not yet been developed to its full potential. In many developed and developing areas stormwater management alternatives have not been fully examined or evaluated in an effort to determine if the existing and future management methods are supplying as much service to the community as possible. Stormwater and the lands required to manage it can provide additional benefits to a community and respond to additional community needs beyond the singular need of drainage. Additional community benefits can be gained by most cities through implementing a multi-purpose stormwater management strategy. This simply means that the stormwater management element of the urban organism must respond to other community needs as well as the single purposed and utilitarian function of draining an area of occassional stormwater.
If a community wishes to increase the efficiency of the urban organism, then stormwater management must serve additional community needs as well as drainage. The challenge is to determine the best additional purposes and uses for this element of the organism based on the conditions existing in and around the community and within the framework of water law.
• • •
m


I. INTRODUCTION


URBAN STORMWATER MANAGEMENT
RESEARCH & CASE STUDY
This document is the conclusion of the first phase of a two phase project. Phase I is a project research phase which is a general overview of urban stormwater principles and practices. Phase II of the project is a case study which applies the information and conclusions generated in Phase I to a specific geographical location. The case study area selected for this project is the urbanizing community of Lafayette, Colorado.
STORMWATER MANAGEMENT & THE URBAN ORGANISM
A dictionary definition of an organism is; "A complex structure of interdependent and subordinate elements whose relations and properties are largely determined by their function in the whole.A vital element of the urban organism is stormwater management. If this element of the urban organism is not functioning properly then it reduces the efficiency (or health) of the entire urban organism. Urban stormwater management is a complex structure of interrelated parts which can be confusing to those who are not a part of the professional community which deal specifically with runoff.
This research was initiated on the presumption that many stormwater management facilities may be functioning adequately from a strictly engineering principle and theory point of view, but from the broader perspective of urban design both the management structures and the land required to manage runoff are community resources which are not developed to their full potential. In most situations, communities can gain additional benefits from the stormwater management element of the urban organism. Research
1


conducted for this project did not disprove the initial presumption. However, the final determination of whether or not stormwater management if fulfilling its potential within the urban organism is left to those who direct the form, function, and visual appearance of public spaces in our communities... the residents.
This research document is a general overview of urban stormwater management principles and practices and is presented to those who wish to elevate their knowledge in this topic area. Efforts for this phase of the project were directed toward providing a basic understanding of urban stormwater management for those who wish to participate more effectively in the following urban processes:
« The process of evaluating the existing or proposed stormwater management element of the urban organism to determine if the element is providing the community with all the benefits that it is capable of providing.
• The development of methods and practices which would determine the optimum additional benefits which could be gained from the management element if it is determined that these facilities are not fulfilling their potential.
Increased stormwater runoff is a problem directly related to urbanization.K J The problem of increased runoff is generally resolved in their outdoor environment. Generally, the problem resolution results in physical forms which become a prominent
2


part of the visual landscape. Structures and spaces required for managing runoff which are a part of the urban landscape and subject to view by the public at large become visual messages which publicize the amount of pride the residents have in their community as well as providing visual evidence regarding the efficiency or health of the urban organism.
SUMMARY:
•This project is a two phase project.
• Phase I is the project research phase which examines the principles and practices of urban stormwater management
• Phase II is a case study wherein the knowledge generated in the first phase is applied to a specific site or location.
• The case study location is the urbanizing community of Lafayette, Colorado.
• A community is an organism comprised of many interdependent elements.
• A vital element of the urban organism is stormwater management.
• In many instances the urban stormwater management element of the urban organism has not been developed to its full potential. The community can gain added benefits from this vital element.


•The information generated for this project research phase is an overview of urban stormwater management principles and practices.
• The research is presented to those who wish to elevate their knowledge of management practices
and principles and for these who wish to participate more effectively in evaluating the benefits the community is gaining from an existing or proposed stormwater management system as well as determining the optimal additional benefits the management element can provide.
• Managing stormwater is a prominent feature in the visual environment.
• The visual forms created by managing stormwater are messages to the public at large which communicate the amount of pride residents have in their community as well as visual evidence regarding the general social health of the community.
• • •
4


RESEARCH SCOPE & SCALE
BETWEEN FLOOD CONTROL & PERCOLATION PITS
For the purposes of this study a distinction is made between flood control and stormwater management. A quote from; Stormwater Management and Design: A Manual of Procedures And Guidelines, will serve as the line of definition between the two subjects of flood control and stormwater management.
"The distinction between stormwater management and flood control often becomes an issue, ...this is essentially a matter of degree, with flooding being associated with the more severe runoff situation. The context of stormwater management may be broadened to include flood control according to personal interpretation of the basic principles of runoff control.
For the purposes of this study, urban stormwater runoff is considered a subordinate but related element of a higher order system which is the flow of water as a consequence of climatological activities over land areas. Urban stormwater runoff is an element within the larger system with its own set of issues, constraints, and opportunities which are distinct but related to other elements of both larger and smaller scale. Figure 1 graphically illustrates the project scope and scale. The element of stormwater runoff for example is a subordinate element of flood control, but superior to mitigation devices such as percolation pits.
5


& ^00 W w*tg—*> ?rrs
_____ -r^ *#£*»-------—
l, „ - wwawi
^ ^ fl2^6
&LU«T|*t4
FIG. 1 PROJECT SCOPE & SCALE
WATER QUALITY - BETWEEN POLLUTION « PCB'S
A hierarchy of scale has been established for the topic of stormwater runoff quality which is similar to the hierarchy established for the topic of stormwater runoff. The discussion of water quality in this document falls between the larger element of water pollution in general and the subordinate element of PCB contamination.

• •
6


PROJECT LOCATION
THE FRONT RANGE URBAN CORRDOR
The specific geographical area selected for applied study is known as the Valley Region which is a subordinate region within the urbanizing belt extending in a north, south direction along the base of the eastern slope of the Colorado Rocky Mountains. This urbanizing belt is referred to locally as, "The Front Range Urban Corridor." The Valley Region is a sub-region located within the geopolitical boundaries which define the Denver Regional Council of Governments. Figure 2 illustrates the contextual location of the Valley Region within the State of Colorado. Figure 3 illustrates the contextual location of the Valley Region within the boundaries of the Denver Regional Council of Governments.
The Valley Region of Colorado is presently experiencing the
r 21
greatest amount of urban growth in the state. This urban-
izing trend is expected to continue for at least the next decade. Land use in this area is changing from primarily agrarian (farming and ranching) to urban and suburban use at a rate commensurate with urban development. This region shares many characteristics with other regions within the front range urban corridor which permits many of the research conclusions and much of the research data to be applied to other areas of the front range.
• • •
7


Fig. 2 at right illustrates the location of the Denver Regional Council of Governments as it relates to the State of Colorado.
Fig. 3 below, illustrates the location of the Valley Region as it relates to the Denver Regional Council of Governments.
«TUDY A.P-SA
na 2
8
FIG. 3
Ifiillfl STUDY AREA &
REGIONAL DEVELOPMENT FRAMEWORK
4 DENVER CBD
r-rw CITY AND COUNTY Of DENVER
V, ^(CENTRAL CITY)
l j---REGIONAL DEVELOPMENT AREAS
; 1---J (URBAN SERVICE AREAS)
â–  RURAL TOWN CENTER A MOUNTAIN DEVELOPMENT AREAS
PLAINS


II. BACKGROUND


THE HYDROLOGIC CYCLE
URBANIZATION & INCREASED RUNOFF
In areas where development has not yet occured, stormwater management is provided by nature. The cycle begins with precipitation (rainfall in this example). A portion of the water is intercepted in the vegetative cover growing on the site and remains on the leaves, branches, and stems and evaporates, never coming in contact with the ground. Some of the water is absorbed into the ground near the surface and is utilized by plants for food and then ultimately returned to the atmosphere through the process of transpiration. Some water infiltrates deep into the ground and replenishes the groundwater supply. A portion of the remaining water collects in depressions in the land surface and remains in place. The water that arrives on the site after all the above storage devices have been used to their capacity flo\vs overland. The flow generally begins as sheet flow, then collects and flows in rivulets, accumulating in both volume and speed as it flows down the watershed through drainageways, streams, and rivers to the ocean where it begins the cycle again. Figure 4 is a simplified illustration of the hydrologic cycle. Figure 5 is a diagram of the hydrologic cycle which illustrates how the hydrologic cycle works schematically.
Urbanization of undeveloped land significantly affects the drainage patterns and processes that existed prior to development. Typical site development processes significantly impact the drainage system that existed prior to site development.
The major impacts to the drainage system are described below:
9


V.
ground water flow
FIG. 4 HYDROLOGIC CYCLE
RAIN (SNOWMELT)
PERVIOUS AREAS IMPERVIOUS AREAS
EVAPORATION
x
_ EVAPORATION INTERCEPTION CTDDAfcC DEPRESSION EVAPORATION .

DEPRESSION
STORAGE
EVAPOTRANS-
"PTrATIOn '
SURFACE RUNOFF
UPPER ZONE FLOW & STORAGE
INFILTRATION
INTERFLOW
"T
I
LOWER ZONE FLOW & STORAGE
+ H
I
SOIL
WATER--------1
MOVEMENT
GROUNDWATER FLOW i STORAGE
FLOW FROM WELLS (SEWAGE)
FLOW FROM SPRINGS & WETLANDS
GEOLGGICAL WATER LOSS
_____________I
FKJ. 5 SCHEMATIC DIAGRAM OF WATERSHED HYDROLOGIC MODEL
10


• Development typically increases the impervious area of a site which reduces the amount of water that was previously absorbed by the soil.
•Vegetative cover is generally reduced which increases the amount of water reaching the ground.
• The surface topography is altered which generally reduces the depression storage capacity of the site with a commensurate increase in overland flow volumes.
The cumulative result of these adjustments to the predevelopment drainage system (providing compensating adjustments are not made to the site) are:
• Development causes a significant change in the volume of overland flow.
• Development causes a significant change in the rate of overland flow.
"Urbanization has required new drainage systems because man was both unwilling to suffer the inconvenience where it could be avoided and because he would not tolerate the loss of life
('4')
or property."^ J
• • •


SUMMARY:
• Development disrupts the drainage systems existing prior to development.
• Development significantly increases the volume and rate of stormwater runoff.
• Increased runoff volumes and accelerated runoff rates resulting from development must be managed to suit the needs of man such as reduce periodic inundation, and mitigate stream bank erosion, sedimentation, and etc.
• • •
12


HISTORIC PERSPECTIVE
A CHANGE IN RUNOFF MANAGEMENT PRINCIPLES
Prior to 1945, most urban development involved small parcels of land. J Stormwater runoff was easily managed using the then prevalent management principle of rapid downstream disposal of surface water. Rapid downstream disposal (the restoration of maximum convenience in the shortest possible period of time by removing stormwater runoff as quickly as possible) was a viable disposal method as long as urbanization was slow and involved relatively small parcels of land. Slow development combined with development on a relatively small scale made the cumulative impacts of rapid downstream disposal difficult to assess. The impacts were adversely affecting the drainage system on the large scale, but the impacts were relatively minor and went unnoticed because of the small scale of development. As illustrated in Figure 6, development began to be conducted on a much larger and more rapid scale in the post 1945 period. It was at this point in time that a more vigorous stormwater management program became necessary because urbanization and its consequent disruption of the existing drainage systems resulted in significant increases in runoff volumes and runoff rates. Upstream developments were passing their increased quantities of runoff to their neighbors located downstream. Rapid disposal became a workable principle in the upper and middle reaches of a watershed, but it created
an unbalanced system which increased the hazard and risk to
(4)
those who resided in the lower reaches of the watershed.
A common practice for managing stormwater in the' pre 1945 period was the combined stormwater and sanitary sewer system. The combined sewer system accepted both sanitary sewage and storm-
13


Fig. 6: In the post 19^5 period, development occurred on a larger scale and at an increased rate. It was at this time that runoff issues had to be addressed with a degree of complexity commensurate with the scale of development and its impacts.
FIG. 6 RELATIVE GROWTH & IMPACTS
water in the same conveyance structures. The conveyance structures usually terminated at a sewage treatment facility (see Figure 7). When a storm occured the increased water load on the system would generally overload the treatment facility.
To avoid overloading the facility the mixed sanitary and stormwater influant was bypassed around the treatment facility and discharged without treatment into the watercourse serving the treatment facility. This practice caused high levels of pollution in streams serving urban areas.^
In the late 1960's and early '70!s a combination of increased problem awareness and pressure from environmental groups prompted federal legislation which dealt with the problems of water pollution through various federal acts. A federal act that had a great impact on the combined sewer system was the Federal Water Pollution Control Act and its amendments (PL 92-500) of 1972. Among other programs, this law established a national permit program for discharges from all point sources - industrial, municipal, commercial, agricultural, and other facilities that release pollutants through pipes and sewers.Since most of


the combined sewer systems discharged through a pipe into a watercourse the implications of this law were to either segregate the sewerage systems or construct treatment facilities that would have the capacity to treat both sanitary sewage and stormwater runoff to a quality level that would satisfy federal discharge criteria. The costs of constructing sewage treatment facilities with enough capacity to treat both sanitary sewage and stormwater began to exceed the benefit of this practice, particulary when the facility would be used at or near capacity only periodically during storms.
The increased hazards posed to downstream residents combined with the implications of the pollution control regulations
f
The system illustrated (right) was the general management system up until the 1970's when it became apparent that such practices were degrading the environment beyond acceptable social and natural tolerance levels.


prompted a reexamination of stormwater management practices. A new stormwater management philosophy emerged; restrict the flow of stormwater leaving a development site to the levels of flow that existed on the site prior to its development. The new philosophy represents a nearly complete reversal of the past management practice of rapid downstream disposal and lays the foundation for a variety of stormwater management structures.
SUMMARY:
• A significant change in stormwater management practices emerged in the mid to late '40's ... from rapid downstream disposal to restricting stormwater flows leaving developed sites to their predeveloped levels.
• The change in stormwater management practices was prompted by; increased hazards to residents in the lower reaches of a watershed, and the segregation of sewage systems.
• • •
16


URBAN RUNOFF
RUNOFF: A SPACE ALLOCATION PROBLEM
There are a number of related issues surrounding the management of stormwater. The major issues can generally be classified into three categories:
• Stormwater quantity and quantity related to time.
• Stormwater quality (pollution) (discussed in the following section)
• Land requried for stormwater management.
The Urban Storm Drainage Criteria Manual states, "Drainage
m
is a space allocation problem.”^ J The following two paragraphs are quoted directly from the Urban Storm Drainage Criteria Manual:
"The volume of water present at a given point in time in an urban region cannot be compressed or diminished. It is a space demand which must be considered in the planning process. Because the space required cannot be altered, choice is limited to location considerations. Where should the water be temporarily stored?"
"Effects on Other Sub-Systems. Channels and storm sewers serve both a conveyance and storage function. When a channel is planned as a conveyance feature,
it requires an outlet ---- available downstream
storage space. When considered as a space demand,
17


the provision of adequate drainage becomes a competing use for space along with other land uses.
If adequate provision is not made in a land use plan for the drainage demand, stormwater runoff will conflict with other land uses and will result in water damages and will impair or even disrupt the functioning of other systems."
The implication of the first paragraph is that the amount of stormwater existing in an urban region is fixed based upon the extent of the development and the amount of precipitation. This amount of stormwater will exist whether or not it is planned for or-managed. The only logical management alternative for planners is where this water is to be stored. It is the location function which can be most effectively manipulated in the management process. The second paragraph addresses the question of the land requried for stormwater management and other competing uses for that land required for management. This paragraph illustrates the importance of including stormwater management as an element in
('O']
land use and community planning.1 J
An aspect of runoff that has not been addressed to this point is that runoff is typically the result of a storm event. It is a fact of nature that storms are periodic and not constant which indicates that the land required for runoff management will only be used for its primary intent of management periodically whenever storm events occur. The remainder of the time (between storm events) the land required for management will not be used for its primary intent. More simply, the land required for management must always exist, but the land will only be utilized for its management function during design
storm events.


1
111
(9
S
<
X
o
<0
5
Post Development Runoff
Pre-Development Runoff
TIME
1. Increased Peak Discharge
2. Reduced Time To Peak
3. Increased Runoff Volume
(2)
FIG. 7a EFFECTS OF DEVELOPMENT ON HYDROLOGIC RESPONSE
Figure 7A illustrates the runoff which must be managed as a consequence of development. The shaded area under the curve represents that runoff which is a result of development without runoff mitigation measures. The impacts of post development runoff are listed below the illustration. It is the mitigation of the following impacts which form the foundation of contemporary stormwater management practices:
• Increased peak discharge
• Shortened time to peak discharge
• Increased runoff volume


HYDROSYSTEM
ELEMENTS
PRECIPITATION
INFILTRATION
INTERCEPTION
TRANSPIRATION
EVAPORATION
OVERLAND FLOW GROUND WATER FLOW CHANNEL FLOW
SURFACE STORAGE
WATER TABLE
FIO. 8 THE HYDROSYSTEM » RUNOFF RELATIONSHIPS
Figure 8 is a matrix which illustrates the relationships between the elements of the hydrosystem, those elements which are a function of runoff quantity, and the elements of the hydrosystem which are typically manipulated to manage stormwater runoff.
20


RUNOFF WATER QUALITY
EROSION, SEDIMENTATION, & NONPOINT SOURCE POLLUTION
Runoff water quality is a relatively new issue in runoff management. Runoff water quality became an issue of environmental concern in the late 1960's and early '70's. The Federal Water Pollution Control Act and its amendments which were enacted into law in the first half of the * 7 0's mandates that, ”... to the extent practicable, waste treatment technology shall be on an area wide basis and provide control or treatment of all point and nonpoint sources of pollution.”^
The United States Environmental Protection Agency definitions of point and nonpoint source pollution are:^
Point Source: "When wastewater is discharged through pipes or sewers it is called a 'point source,' and this form of pollution is controlled through a national permit system which issues individual permits prescribing the types and amounts of pollutants that a municipality or an industry can discharge into waterways."
Nonpoint Sources: "... pollution that is carried over land by rainwater or melting snow or which seeps through the earth and enters waterways in a general manner net through a pipe or sewer."


Figure 9 illustrates the differences between point and nonpoint pollution sources.
In their book, Handbook of Nonpoint Pollution, Novotny and Chesters propose the following as a summary of ...
differences between point and nonpoint pollution sources'"
Point Sources
Fairly steady flow and quality. Variability ranges less than one order of magnitude.
The most severe impact is during low flow summer periods
Enters receiving water at identifiable points
Primary parameters of interest: BOD, dissolved oxygen, nutrients, and suspended solids.
Nonpoint Sources
Highly dynamic in random, intermittent intervals. Variability often ranges more than several orders of magnitude.
The most severe impact during or following a storm event.
Point of entry often cannot be identified or defined.
Primary parameters of interest: Sediment, nutrients, toxic substances, pH, and dissolved oxygen.
FIG. 9 A COMPARISON OF POINT A NONPOINT POLLUTION SOURCES
Within the Valley Region, and the Denver Regional Council of Governments' boundaries, studies are now being conducted regarding water quality. At the present time the data collection phase of the study is in the final stages. A publication of the data is projected for January, 1983. These data will be useful for determining baselines and trends as well as periodicity of pollution elements contained in stormwater. A subject of significant importance is the determination of adverse environmental impact on streams and waterways; the extent of impact, and if runoff pollution even causes any significant adverse impacts. According to the Denver Regional Council of Governments however, it will be approximately another ten years
22


before mitigation systems will begin to be put in place if it
f 31
is determined that they are necessary.v J This time figure depends upon the emphasis and initiative regarding runoff water quality management remaining the same as it is at the present time. On a larger scale, not specific to the Valley Region, the literature reviewed for this document demonstrates that a sizable amount of study has been conducted in the area of stormwater runoff nonpoint source pollution. Study is currently being vigorously conducted in the following categories:
• Surface water problems
• Hydrologic considerations as related to nonpoint pollution
• Runoff water pollution from the atmosphere
•Erosion and sedimentation
• Interaction of pollutants with soils
•Groundwater pollution
•Pollution from impervious urban areas
•Nonpoint pollution simulation models
•Land use and nonpoint pollution
•Management practices of nonpoint pollution control
• Planning for nonpoint pollution control


A study conducted for the Regional Transportation District has concluded that most of the aquifer recharge areas underlying the major water courses in the Valley Region are presently contaminated. If runoff water quality is not improved it could threaten the use of these aquifers as potable water supply sources.
An aspect of stormwater management that is being investigated and is prompting action in the Valley Region is erosion and sediment control. Draft documents which will comprise the Denver Regional Council of Governments' best management practices manual deliniate the costs of erosion control and sedimentation mitigation. ('11^ Additional information
on methods and practices of erosion control and sedimentation management can be found throughout the literature.
Consequences of erosion and sedimentation include; soil loss, watercourse turbidity, modification of hydraulic profiles of runoff conveyance systems, chemical transport, siltaticn, and etc. The problem is generally being addressed at
the site of construction or disturbance. Areas that are not being disturbed by development activities often contribute to the sedimentation problem. Management techniques used in undeveloped areas usually attempt to reduce runoff velocity so that particle erosion is minimized. Land use and management practices are also being used to promote vegetative cover which reduces runoff velocity and consequent particle transport.
The Environmental Protection Agency has prepared a set of categories for which selected water quality criteria have been established. Figure 10 lists selected water quality criteria for surface waters. Figure 11 is an outline of factors which determine pollutional loadings from urban areas. The criteria


is generated from an organization of categories which are listed below;
• Problems with sediment
• Dissolved oxygen and biodegradable organics
• Nutrient contribution and eutrophication •Toxic chemicals and metals
• pH
(•)
FIG. 10 SELECTED SURFACE WATER QUALITY CRITERIA
Parameter Primary (Contact) Recreation Fish and Wildlife Protection and Propagation Warm Water Cold Water Marine
PH Total alkalinity 6J-8.3 6-S 6-9 6.7-85“
(mg CaCOj/liter) Turbidity >20 >20 “
Secchi disk (m) >12 - — -
Jackson Units Max. temperature ~ <50 <10 _
ro Max. temperature <30 <20 ~
increase (°C) <2.8b <2.8b <0.8C <2.2d
Change in salinity Dirsolved oxygen <10% of natural variations
(mg/liter) Total phosphorus >5 >6
(ug/liter) Cob form median MPN <100“ <100'
(Noil00 ml) Fecal coliforms (No./100 ml) <200* <70f
“Normal pH range should not be altered by more than 0.1 pH units.
"For lakes <1.6*C.
“Period June-August.
^Period September-May.
“For stream entering lakes <50 ug/Iiter.
*For waters used for shellfish cultivation and harvesting. Maximum of 10% of samples not to exceed MPN of 230/100 ml for five tbe tests.
•Maximum of 10% of samples not to exceed 400/100 ml during any 30-day period.
25


THE FOLLOWING LIST OF FACTORS IS PROPOSED BY NOVOTNY & CHESTERS IN THEIR BOOK: HANDBOOK OF NONPOINT POLLUTION.
"A partial list of factors that determine poliutional loadings from areal sources and their relation to land uses are listed as follows."
1. Factors strongly affecting pollution generation and correlated closely with land uses:
a. Population density.
b. Atmospheric fallout.
c. Degree of impervious area usually correlated with population density.
d. Vegetation cover.
e. Street litter accumulation rates.
f. Traffic density.
g. Curb density and height.
h. Street cleaning practices.
i. Pollution conveyance systems
2. Factors strongly affecting pollution generation but correlated poorly with land uses:
a. Street surface conditions.
b. Degree of impervious area directly connected to a channel.
c. Delivery ratio.
d. Surface storage.
e. Organic and nutrient content of soils.
3. Factors st'origly affecting pollution generation but unrelated to land uses:
a. Meteorologic factors.
b. Soil characteristics and composition.
c. Permeability.
d. Slope.
e. Geographical factors.
m
PH. 11 LAND UK t POLLUTION LOADMQ
Many of the conflicts between mitigation measures for water quantity and water quality have not yet been clearly identified. An example of how solving a runoff quantity problem can conflict with the mitigation of water quality is the common curb and gutter. The curb and gutter are usually implemented to direct/ channel runoff water. However, these same structures can become catchments which collect sediments and pollutants. It has been observed and documented that 80% of street refuse can be found within 5.9 inches of the curb and over 951 of all
r 9 q
street refuse will be within 3 feet of the curb structure.
When a storm generates enough runoff to begin flow along the gutter, the pollution is carried by the flow and deposited in the catchment/watercourse.
26


Water quality is a definite issue in urban stormwater management and the environment. (18) (-*-9) Data in this area however, are not as complete as the data available for stormwater runoff quantity. Although the objectives and goals of managing runoff quantity may at times be elusive, the objectives of runoff quality management are even less clearly defined at this point in time. There is one issue that is conclusive; the designer/ planner will have another level of complexity to deal with in urban stormwater management, and that is stormwater quality.
Implicit in this discussion of runoff water quality is the possibility of designed obsolesence. If the designer today does not think to the future when designing management structures and devices for present use, it is very likely the costs of retrofitting present structures in the future to improve water quality will be very costly.
• • •
27


MANAGEMENT METHODS
A RUNOFF MANAGEMENT PRIMER
The Urban Stormwater Criteria Manual prepared for the Denver Regional Council of Governments defines two distinct storm events and their associated drainage systems. These events are defined as the major and initial events and related systems. They are defined as follows:
"Initial Drainage System: That storm drainage system which is used for the collecting, transporting, and disposing of snowmelt, miscellaneous minor flows, and storm runoff up to the capacity of the system. The capacity should be equal to the maximum rate of runoff to be expected from the initial design storm which may have a frequency occurrence of once in 2, 5, or 10 years.
The initial system is sometimes termed the 'convenience system,' 'minor system,' or the 'storm sewer system.'
The initial system may include many features ranging from curbs and gutters to storm sewer pipes and open drainageways."
"Major Drainage System: That storm drainage system which carries the runoff from a storm having a frequency of occurrence of once in 100 years. The major system will function whether or not improvements are situated wisely


in respect to it.
The major storm system usually includes many features such as streets, gulches, and major drainage channels. Storm sewer systems may reduce the flow in many parts of the major drainage system by storing and transporting water underground.
The good planning and designing of a major system should eliminate major damage and loss of life from storms having a one percent chance of occurring in
m
any given year.MV- J
Figure 12 illustrates the three management practices in current use.
FIG. 12 COMBINED MANAGEMENT STRATEGIES


Management Practices: These practices are often referred to as nonstructural mitigation practices of stormwater effects. These practices include: land use planning and regulation, flood insurance, flood proofing of structures, ordinances covering the mitigation of stormwater runoff effects, street maintenance, open space, and site design methods.
The disadvantage of some of these practices is that they are often difficult to implement, regulate, and enforce.
Structural Practices: This method will be sub-divided into two categories.for this study. They will be defined as "hard" structure design and "soft" structure design. As the title indicates, structural practices include the use of structures for managing runoff. Hard structures include the use of engineered structures such as concrete drop structures, conduits, and etc. Such structures are designed with the primary objective of managing stormwater only, with little regard for the visual surroundings and contextual relationships between the structure and adjacent land use. Soft designs are those that maximize the natural drainages and conditions on the site for the management of runoff. Soft structures are designed to be compatible with surrounding land uses. Generally, hard design practices are less land consumptive than soft design responses.
Combination of structural and management practices:
This third category is a comprehensive practice of management techniques which combine both non-structural


and structural practices to manage runoff. This combined practice generally results in the most satisfactory management response. The primary disadvantage of this practice is that it requires an interdisciplinary design approach to generate a comprehensive master plan for stormwater management. Once the plan is formalized and approved, appropriate measures must be established to insure that the plan is complied with and the objectives of the plan are enforceable. Many communities lack the institutional resources for this practice.
There are numerous structural devices and methods which can be used for the management of runoff. Such structures can be used singularly or in conjunction with other management structures and techniques. The various structural devices are categorized according to the elements of the hydrologic cycle that are being controlled. •
• Infiltration methods/devices: Methods which manage runoff through enhancing the natural process of infiltration/percolation attempt to reduce the total volume of runoff and consequently decrease the peak discharge rate of the runoff leaving a site.
This method has the effect of reducing the amount of precipitation that becomes runoff. Infiltration devices are generally not capable of managing relatively large volumes of runoff because of soil absorption rates which are usually less than the rate of precipitation accumulation. Infiltration devices can be used for management of relatively small volumes of runoff (roof drains, small parking lots, and etc.) or they can be used in conjunction with


other devices which do not rely on infiltration
for runoff management. Specific structures/techniques
for infiltration management are:
• Infiltration Basins
• Infiltration Beds
• Infiltration Wells
• Porous Pavement
Such structures require soil analysis which will determine the absorption rate of the soils surrounding the devices. The absorption rate will
determine the efficiency of the management structure.
• Detention/Retention Facilities: These structures
enhance the surface storage element of the hydrologic system. These structures are intended to reduce the peak discharge of the runoff leaving the site. A distinction is made between detention facilities and retention facilities in that retention facilities typically hold stormwater for longer periods of time and release it at a much slower rate. Retention structures are generally larger than detention structures because retention structures usually manage larger volumes of water. Infiltration may take place in these structures but infiltration is not a design consideration in most applications. There are numerous forms of these devices, but they can usually be broadly categorized as follows:


• Detention/Retention Basins
• Detention/Retention Tanks
• Permanent Ponds
•Multiple Use Impoundment Areas:
Parking Lot Detention Areas Roof-top Retention
• Road Embankment Structures
• Conveyance Structures
Underground piping systems Open channels
Figures 13, 14, 15, and 16 are matrices which provide a summary of considerations when selecting the management device or structure that will provide the desired runoff response.
— £ ce
lu X —
DETENTION/RETENTION BASINS
DETENTION/RETENTION TANKS
DETENTION/RETENTION PONDS
PARKING LOT DETENTION
ROOF-TOP RETENTION
OPEN SPACE DETENTION
ROAD EMBANKMENT DETENTION
INFILTRATION BASINS
INFILTRATION BEDS
INFILTRATION WELLS
POROUS PAVEMENT
OPEN CHANNELS
PIPE SYSTEM,S
(t)
m. 1» OKRATWO * HAarTOUMCC CONMJQUTOMS
33


5 S
S
LAND ACQUISITION
EXCAVATION & FILL
EROSION PROTECTION
FENCING
WELL DRILLING
WELL CASING
INLET STRUCTURE
SEDIMEMT/PEBRIS CONTROL
I SOIL PERMEABILITY__________
GROUND WATER LEVEL__________
I GROUND WATER SUPPLY________
{structural SOIL LIMITATIONS LANDSCAPING
[ENGINEERING & SITE DESIGN [OPERATION 8 MAINTENANCE
FINANCING___________________
| SFWER SEPTIC FIELDS DEPTH TO BEDROCK
PKL 14 CONSOCIATIONS RELEVANT TO
. ACQUISITION OF LAND EXCLUSIVELY CONSTRUCTION OF CONTROL STRUCTURES . FENCING SERVICING SECURITY/SAFETY PURPOSES . REGRADING, NEW ROADS, NEW BRIDGES, ETC.
. CHANGES IN DESIGN (ROOF TOPS, PARKING LOTS, ETC.) SERVING A CONTROL FUNCTION
CO PO
â– â– â– â– â– 
LAND ACQUISITION (1)
EXCAVATION & FILL
EROSION PROTECTION
FENCING (2)
PUMPING FACILITIES
PIPING
INLET STRUCTURE
HYDRALIC CONTROL DEVICE (OUTLET)
SPILLWAY STRUCTURE (OUTFALL) MULTI-PURPOSE USE
MODIFICATION OF EXISTING FEATURES (3)
MODIFICATION OF EXISTING STRUCTURES (4) LANDSCAPING
ENGINEERING S SITE DESIGN
OPERATION & MAINTENANCE_________________
FINANCING
EASMENT/ACCESS


NATURAL CHANNEL_________
CHANNELIZED DRAINAGEWAY ARTIFICIAL OPEN CHANNEL
PIPE SYSTEM_____________
CULVERT
FKL 1« CONSOERATIONS RELEVANT to channel a conduit oemon
'«)
Another aspect o£ stormwater runoff management is the location of the devices used for runoff management. The location in the drainage basin where management structures are placed relative to the natural drainage patterns has a significant influence on the effectiveness of the management structures. There are three broad categories of location alternatives.
The three locations (listed below) also reflect the relative scale of runoff which must be managed in each drainage basin. The three location alternatives are:
• On-Site Control
• Off-Site Control
• In-Stream Control


Figure 17 illustrates the three management structure location alternatives.
pcv^LofMcur *rre
£FP4rre <£*?vrr*T?l_ (i^’Vre.on rpfenf -tfnjatn)
â– *rru
G*6.Ner-*4,\_-r' makidktbc* Merui»& in VALue-V timb.
d.0F*Ffie>L-
3 TYPI6AU U^CA>T)0M6
i. Fn. 17 UANAOEMENT STWKTUHE LOCATIONS
On-Site Control: Structures located on the development site are generally intended to manage the runoff which is a result of site development. Such structures (infiltration, detention, retention, etc. are located on the developed site and resolve runoff issues prior to the water leaving the site.
36


Off-Site Control: Structures located off the development site are generally used to manage runoff from a collection of developed sites. Such structures are generally larger in size thus making them more land consumptive than on-site structures.
In-Stream Control: Structures that manage runoff in-stream are usually large in scope and scale (dams, reservois, etc.). Such structures are generally used for managing runoff from less frequent storm events such as the 25-100 year storm. Structures of this size and scope are generally used for flood control and management of runoff on a regional scale. Managing the adverse effects of runoff from developed sites usually has two aspects which have to be considered, The first aspect has been discussed in the previous sections on runoff management structures which addresses the preliminary collection and mitigation of volume and volume related to time problems. The second aspect of management is the conveyance of stormwater which has been collected and managed on site from the site or management facility to a major waterway or drainageway. Conveyance structures can be categorized according to two basic types. The first type is the conduit or underground conveyance device. These structures are generally in the form of pipes and similar structures which are generally thought of as stormsewers. This method of conveyance can be more costly than open channel conveyance structures, but if land values are relatively high and underground systems result in additional revenue generating development, then such systems may be more economical than alternative conveyance structures.
The second type of conveyance structure is the open channel type. Such structures vary in size and appearance and can be designed to be a development site amenity. The majority of conveyance structures in the Valley Region are the open channel type.
37


ADVANTAGES OF THE WATERSHED APPROACH
Stormwater management is a complex system of interrelated elements that are more effectively coordinated and implemented on a regional/watershed scale. Weston and Associates states:
"In terms of stormwater management, the watershed approach entails a more comprehensive consideration of related issues. Included in this consideration is the effectiveness of different techniques such as land use planning, site design, and regional in-stream structures. The objective of the watershed approach is to achieve the best combination of alternative stormwater management measures.
Overall, larger reservoir types of structures, in most cases, are more cost effective from a cost/benefit standpoint than on-site and off-site measures. This is due to the economics of scale involved as well as to the value of multiple-use benefits. Another advantage of the larger more regional control structure is more practical maintenance. Several smaller on-site structures often become unmanageable in terms of quality control and inspection during construction, and subsequent operation and maintenance. Funding and enforcement of pertinent regulations also become less complicated issues with larger regional structures. However, the planning and approval stages for regional control structures can be very complex and drawn out.
More thought must be given to the proposals


such as drainage taxes and fees in order to make the implementation of regional stormwater management structures more prevalent.
In the immediate time frame, however, on-site runoff control seems to be the most practical and easiest to implement. On-site control, although not the ultimate solution to runoff problems, is an effective method of control and can play an important role, even in a regional context.^
• • •
39


THE SOCIAL SYSTEM
THE EXTENT TO WHICH RUNOFF IS MANAGED
The terra social system,for the purposes of this document, is taken to mean the systems and institutions created to deal with runoff and runoff management. There are two areas of concern in the social system. The first is the cultural/social environments determined by the residents of a community. Residents determine the type and kind of community in which they live as well as the services they wish their community to provide. It is the desires and aspirations of the residents of a community which prompts them to create and sustain city staffs of administrators, planners, parks directors, maintenance crews, and etc...the institutional support which works to bring the desires of the community to fruition. The second area of concern is the institutional systems which are in place to support and sustain community services, goals and objectives. It has already been determined at the regional scale that stormwater runoff is to be managed. The extent to which it is managed is largely determined by the residents of the local community.
The local community can elect to fulfill its minimal obligations in this matter, or the community may select to pursue a course which will yield them a management system which can be a community asset that responds to community needs over and above mere drainage.
The degree or extent that stormwater management systems are utilized and the extent of their efficiency is largely a function of the community institutional support facilities required for development review, approval, inspection, enforcement, and maintenance of public land and structures of all types as well as runoff management structures.
40


Community scale stormwater management is a large scale problem. Many agencies have been created to assist communities with developing stormwater management plans. These agencies have been created at all levels of government from relatively local agencies to the federal level. The assistance that these various agencies can provide varies from technical, and legal aid, to financial assistance. These agencies can be broadly categorized on the basis of the organizing entitles such as; federal, state, county, district, and private and cooperative agencies. The primary concern of all agencies is generally to promote stormwater management plans which not only serve the need of specific communities, but the region as a whole. The objective of these various agencies is to implement a logical and efficient management system that is appropriate to the conditions existing at the regional scale.
The selection of what agencies are selected for assistance will
be based largely on the development site, and the type of
management devices and principles selected for management. In
the Valley Region there are several agencies at all levels of
government which can supply information and other assistance.
From a general perspective these agencies have varying degrees
of influence and little direct enforcement powers. Most of the
agencies in the Valley Region are informational and organizational
in nature. The enforcement aspects are generally delegated to
f 21')
the local communities within the region.
From the legal perspective, a logic that can be followed under many, but not all situations is that the federal laws generally mandate broad guidelines and procedures, as well as certain minimum criteria of compliance. The individual states are permitted to formulate legislation toward compliance standards within the federal context. The state then forms its legislation


along the same format to allow the local governments to establish their own criteria within state and federal guidelines and mandates. This philosophy is intended to allow for legislative latitude to accommodate local conditions. The general logic then, is if the management designs are in compliance with the criteria generated at the local level, or the closest level of government, then it is very likely that the designs will meet the requirements of governmental entities progressively removed from the local level. If designs comply with a city's ordinances, the designs will likely comply with all other agencies; county, state, etc. The local level of government in the Valley Region is usually charged with the formulation, maintenance, and enforcement of ordinances, and codes. A cautionary note at this point is to investigate the particular system and area that is to be managed to be sure that this logic is valid for the specific design problem.
iMost of the agencies that can provide assistance in designing and implementing runoff management systems can be broadly categorized as follows:
• Flood Control/Floodplain Management
• Erosion and Sediment Control
• Water Treatment and Resue
• Water Supply Development
Two important agencies which must be considered when designing management systems in the Valley Region are: The Urban Flood and Drainage Control District and The Denver Regional Council of Governments. Ancillary agencies should also be consulted for


additional information and possible sources of funding. Some of these agencies are: Colorado Department of Highways (possible funding for bikeways and etc.), Department of Natural Resources -Game and Fish, Parks and Recreation - these and other agencies can supply information regarding multiple uses for stormwater and the lands requried for stormwater runoff management.
From a water law standpoint, the Constitution of the State of Colorado regards Water rights as personal property. One significant point that emerges out of this attitude is the effect proprietary rights have on impoundment. Stormwater runoff management and the facilities and actions necessary for managing stormwater are subordinate to the water rights of upstream and downstream users and subscribers. The concept of proprietary rights translates into the situation whereby additional runoff resulting from urbanizing activities must be managed, but the extent of management must not interfere with the historic flows which existed on the site prior to its development.
The current management philosophy (which in many instances is
the law) is: the water falling on a given site shall be, in an
ideal design situation, absorbed or retained onsite to the
extent that after development the quantity and rate of water
leaving the site would not be significantly different than if the
(4)
site had remained undeveloped.^ J Although the philosophy just
stated implies that the rate and quantity of runoff as a result
of development be contained on the development site, it is
unlikely that one would be faulted for adding more water to the
system providing that additional water did not disrupt the
(22)
hydraulic designs of the overall system. J Implicit in this statement is the idea that the amount of water added to a watercourse is not as critical an issue as when that additional water
43


arrives at the major watercourse and is conveyed through it.
This is an especially important concept in the Valley Region since this region experiences long and seasonal periods of soil moisture deficit during which times the watercourses are not flowing at full capacity. It is during such moisture deficient periods that stored runoff could be added to the watercourses. Adding water to the watercourses then, would be a function of time and watercourse capacity.
There are several federal level programs which have been formulated as a result of various federal legislation. Some of the more significant legislation that affects stormwater runoff management and establishes criteria for management are:
• The Federal Watershed Protection and Flood Prevention Act: (PL 83-566) of 1954. This legislation authorizes the Soil Conservation Service to aid state and local agencies in planning watershed projects, and provide funding for project implementation. The objective of the projects is flood control and upstream watershed conservation. The methods by which the objectives are attained are both structural and non-structural.
• The Federal Water Quality Act of 1965: This act * •
influences stormwater runoff management in that it mandates certain guidelines and procedures for the quality of stormwater. This legislation brings into focus the issue of nonpoint source pollution migitation.
• The Water Resources Planning Act of 1965: This act directs the Army Corps of Engineers to consider non-structural techniques of controlling runoff in addition to traditional structural mitigation techniques used for flood control.


• The National Flood Insurance Act of 1968: The National
Flood Insurance Program which is administered by the
Federal Insurance Administration of the Federal
Emergency Management Agency. The requirement that 100
year floodplains be defined and regulations created and
enforced regarding development in the areas of flood
hazard has established a strong precedent in all phases
of stormwater management. In addition, such action
has established a strong relationship between land use
f 2!
control and stormwater management in general.
• The National Environmental Policy Act of 1970: This act contains very general references to stormwater management, water quality, and environmental standards. The impact
of the act is in the area of establishing planning frameworks, and public participation requirements for federal projects.
SUMMARY:
• The social aspects of stormwater management can be categorized into two elements.
The goals and objectives of the residents of the community
The institutional support for achieving and sustaining the community's goals and objectives
• There are numerous agencies created to assist local communities with stormwater management. Such agencies exist at all levels of government. •
• The communities are generally the controlling and enforcing agency regarding stormwater management at


the local level. Communities are required to meet criteria for management which has been created at the larger - regional scale.
• Stormwater management does not take precedence to the water rights of individual subscribers.
• The residents of a community determine the effectiveness of stormwater management principles and the extent to which they want their management system to satisfy community needs in addition to managing stormwater.
© • ©
46


III. INTERPRETATION


IMPLICATIONS OF TRENDS & PRACTICES
The following examination of trends and practices and their implications is an organizational device which relates current trends in runoff management in the Valley Region to the possible implications and consequences of those trends. Trend analysis forces an examination of possible future consequences of current decisions. The objective is to use the device as a control element to assure that the solution to the present problem doesn't create additional problems in the future.
A concurrent benefit of trend and implication analysis is that it provides an indication of the changing management methods and the strength or momentum of the infrastructural elements created to perpetuate those methods. Determining the momentum or strength behind management methods assists the planner/designer in defining the social system tolerance levels which determines the acceptability of alternative or multiple use plans and designs.
There has been no attempt to evaluate whether the current trends and practices and their related implications are positive or negative, good or bad. Evaluation of practices and implications is a function of the design objectives and the specific objectives of the management principles should be generated on a case to case, site to site basis.


CURRENT TREND/PRACTICE
The on-site deterition/retention of runoff resulting
from development/urbanization.
IMPLICATIONS
Generally reduces costs of conveyance that would otherwise have to be implemented for rapid disposal of runoff.
Many community ordinances are ill-defined which
results in detention/retention facility locations
haphazard and uncoordinated. Facitlity site
selection is based on criteria other than management (93 \
master planning.' '
Lack of master planning and site conditions when
determining facility location can increase total
development construction costs by removing potentially
123)
salable land from development.' '
(23)
Can increase citizen tax burden' '
• communal maintenance costs for maintaining structures which may not be necessary
• land required for runoff management is removed from community tax roles
(23)
Potentially increased tort liability


CURRENT TREND/PRACTICE
The on-site detention/retention of runoff resulting
from developmerit/urbanization - continued
IMPLICATIONS
Possible adverse effects on neighborhood property
i (23) values'
Facilities can be unsightly & disfunctional if not properly maintained
Reduced sediment loads on downstream systems can adversely affect drainageway longitudinal hydraulic profiles which can alter system efficiencies.
Communities risk implementing an overall inefficient
system by utilizing detention/retention structures
(23)
out of context with site conditions.'
Possible health hazard if faci1ities/structures are not properly maintained. Structures can become breeding areas for insects & catch basins for toxic sediments.
Retention/detention structures can improve water quality through settling & precipitation of sediments providing runoff is detained for an adequate length of time (24-48 hours).


CURRENT TREND/PRACTICE
The on-site retention/detention of runoff resulting
from development/urbanization - continued
Many communities are still using runoff structures which were implemented under the historic management principle of expedient removal of runoff.
IMPLICATIONS
Many communities disregard the relationship between retention/detention facility requirements and the size of development. Developments which are relatively small may not contribute a significant amount of water to the system and thus not have a significant impact on stormwater systems... such developments may not require detention/retention facilites.
Potential future conflicts with water resource development.
Reduced aquifer recharge along natural water courses
Small impoundments haphazardly located add to the costs of consolidation if it becomes desirable to utilize impounded runoff water for potable supplies, or to implement a regional or large scale basin wide runoff collection and water utilization system.
Interfacing of "new" & "old" systems must be incorporated into the process of determining a contemporary stormwater management system.


CURRENT TREND/PRACTICE
The current principle of using retention/detention
facilities as a major element in runoff management
(3)
is primarily applicable to new developments. '
A trend toward the utilization of natural drainage systems has been expressed by the residents of urban communities.
Ol
IMPLICATIONS
The cost/benefit in many instances precludes retrofitting of developments constructed prior to retention/detention management criteria.
A clear understanding of the term "natural" between the designer & the public is necessary in order to provide an acceptable design response... true natural drainage systems can be land consumptive & tend to dictate land use rather than respond to development impacts.
There is a distinction between natural drainage systems and natural appearing drainage systems.
That distinction must be clearly defined between designer/planner & client.
A determination of definition is required ... is this trend an expression of public attitude which states that they find "hard" management structures such as concrete armored channels, concrete drop structures, and corregated steel culverts less attractive and appealing than "soft" management


CURRENT TREND/PRACTICE
A trend toward the utilization of natural drainage systems has been expressed by the residents of urban communities - continued
Runoff water quality issues are now beginning to be examined & mitigating procedures being formulated.
IMPLICATIONS
devices and structures such as blue/green ways, landscaped open spaces, and pocket parks that accompolish the same runoff management objectives
Natural/natural appearing management systems can be a visual site attributte.
Such systems provide a wider range of design options
Such systems permit multiple uses for the land required for the management of runoff
Such systems can be maintenance intensive
Systems can be more land consumptive than "hard" systems
Mitigation of poor runoff water quality can improve groundwater quality.


CURRENT TREND/PRACTICE
Runoff water quality - continued
There is an increasing trend of filing for the water
(31
rights on runoff resulting from development. '
Communities are implementing non-structural management measures (best management practices) to mitigate the adverse effects of runoff.
IMPLICATIONS
Improvement of runoff water quality can ease the burden on downstream water treatment facilities.
Conflicts can arise between the best methods for improving water quality & managing runoff quantity since problem resolution techniques between the two are not necessarily compatible
Legal & legislative communities have as yet provided a clear policy in this area. This trend will require additional legal clarification.
This trend will initiate principles which will likely require the runoff to be used as a resource rather than a liability. Generally, water which has been filed on must be used or the rights to it are lost.
Street sweeping equipment & similar devices are being used to mitigate both pollution and sediment problems in communities. This requires a relatively intense maintenance program since it has been observed that street sweeping equipment is effective in mitigating pollution & sediment loading only


CURRENT TREND/PRACTICE
Non-sturctural management - continued
Communities in the valley region are initiating drainage master plans and integrating them into the community planning and design process.
Multiple use facilities with a runoff management function are now being examined and planned in valley region communities.
IMPLICATIONS
when repetitive passes are made with the equipment.
The effectiveness of street sweeping is based on
the maintenance program since the efficiency of the
(9)
sweeping equipment is relatively low.
Non-structural practices are prompting alternative site planning measures and movement system layouts designed to mitigate runoff problems.
The results of integrated planning techniques is an urban environment that is generally more efficient & attractive.
Integrated planning processes which address drainage issues generally prompt planning decisions which have significant effects on land/property values.
Such facilities generally require the formation of a multi-discipline design/planning team for optimum results.
Multiple use facilities can reduce costs to communities if properly programmed. Costs can be


CURRENT TRENDS/PRACTICES
Multiple use facilities - continued
Communities in the valley region have adopted criteria for evaluating both the initial and major storm drainage systems.
IMPLICATIONS
significantly reduced for land acquisition & facility maintenance by combining park & recreation facilities with stormwater management systems.
Multiple purpose systems broaden possible funding resources.
Increased use of open space
Increased outdoor recreation area
Can improve the visual & aesthetic environments of neighborhoods & communities.
Requires interfacing of runoff management systems with other community systems.
The Urban Drainage Criteria Manual^ has been adopted by every community in the valley region.
This document provides a basis of organization of methods, processes, & goal definition. The document provides the framework for management which works toward a coordinated regional management plan.


CURRENT TREND/PRACTICE
Addoption of ordinances in many communities regarding
runoff management and erosion control take two
(l?l forms: '
Direct address wherein the ordinances are clearly defined under drainage headings.
Indirect address wherein the ordinances are not stated under classifications which deal specifically with runoff, but compliance with the ordinance will affect runoff.
Although many of the legislative systems are
comparatively streamlined, the legal community
generally still resolves conflicts in this area on a
(23)
case to case basis founded in applicable law. '
IMPLICATIONS
Such a practice requires that the designer/ planner of developments as well as the permitting agency must have a thorough knowledge of city ordinances & policies.
Ordinances may not be compatible with each other.
In many instances, the legal requirements are incompatible with the natural & social conditions existing in an area of development. A situation develops where laws are written for large scale applications & are expected to fulfill the requirements of development which usually takes place at a much smaller scale. This creates a situation of ambiguity which at the present time must be resolved in the preliminary design phase or through some method of mediation after the preliminary design phase when it has been discovered that a social or natural system's tolerance level has been exceeded.


CURRENT TREND/PRACTICE
A general overall awareness regarding the aesthetic impacts of runoff management structures is apparent. Studies are being conducted as to the social appropriateness of management structures when related to the sociocultural profiles and proximity of residential development.
Cl
•Nj
IMPLICATIONS
What structures are appropriate for the social context in which they are placed ... will some structure types be less subject to vandalism, create an environment for anti-social behavior?
These questions are in the process of being answered.
Questions regarding the socio-economic tolerance level of the users will have to be resolved on a individual community/site basis. It must be determined if the residents will contribute indirect or- direct financial support for aesthetics, and what the extent of that support will be.
The socio-economic profile of the user group can determine the type of management practices and devices used for runoff management.
Cost/benefit of management devices ... does the type of management enhance the marketability of a development? If it does... to what extent is the marketability enhanced?


CURRENT TREND/PRACTICE
Multiple purpose facilities recieve a higher level of
priority from institutional systems when requesting
runoff management/drainage assistance.^
Recent governmental fiscal policies have reduced the the amount of funding available to communities
IMPLICATIONS
This should encourage communities to investigate the multiple purposes stormwater management devices can provide.
Will encourage the development of multiple use plans and the implementation of multiple use devices.
Communities will have to become more efficient in managing their urban environments if the quality of life is to remain the same or improve.
There is less funding for:
Design Review
Inspection
Enforcement
Planning
Maintenance
Ordinance Review
Ordinance Upgrading
Ordinance preparation & Enactment
Etc.
Less action in the above categories can lead to a reduction in the quality of life for community residents.


CONCLUSIONS
SITE FACTORS DETERMINE DESIGN RESPONSE
Generalized comments about complex topics, such as urban stormwater management, are subject to controversy because no general statement is correct at all times and under all circumstances. Reviewers who are trained and educated in the scientific methodology are expected to find the following conclusions especially frustrating because the comments are overviews; and as such do not focus on narrowly defined facets of runoff management which have been investigated within clearly defined boundaries, at a prescribed point in time, and under a specific set of conditions. This document is an overview investigation of urban stormwater management in the Valley Region of Colorado, and as such it is obligated to take a holistic and generalized view of the situation, and derive holistic and generalized conclusions based on the research conducted.
Runoff management in the Valley Region is organized under a general strategy which allows a wide latitude of management options at the community level. These options are intended to be exercised at the local community level within the context of the regional strategy. A policy of multiple purposes for stormwater runoff and the lands used for its management is strongly
'71
encouraged in the Urban Drainage Criteria Manual.1 The result of this multiple purpose policy is a wide range of management options which can be implemented at the community level. Unfortunately, many communities do not take full advantage of this wide range of management option and the consequences of this unexploited advantage are environments which do not fulfill their community benefit potential. This typically results in management structures and systems that are singular in purpose; which do not
59


serve the neighborhood, community, or region to maximum advantage. Research for this document demonstrated that in many instances management structures which are perfunctorily installed for the single purpose of controlling runoff auanity without responding to local conditions and parameters are not cost efficient to the developer or the community, detract from the neighborhood and community image, and can, in fact, be detrimental to the overall regional scale runoff management strategy.
In order to develop runoff management strategies which respond to a variety of community needs, the tolerance levels of both the natural and social environments must be determined at both the regional and community scales. Once these levels have been determined the extent to which the management objectives exceeds the natural and social environments' tolerance levels can be reasonably evaluated. At this point, the impacts of management decisions can be evaluated and options and alternatives can be more efficiently assessed.
A key issue in runoff management is the formulation of goals and objectives. Although the Urban Drainage Criteria Manual implies a strategy of runoff quantity management as the major objective, the strategy is broad enough in scope to permit multiple use concepts for both the land utilized for runoff management and the additional runoff water generated as a result of urbanizing activities. The most effective and efficient point in the management system to initiate plans for multiple uses is at the point in the process where management objectives are determined. The general objective should be expanded from the singular one of managing quantity problems alone, to managing quantity problems while enhancing the natural and social environments of the community. A concept that could be broadly applied within the Valley Region would be to internalize and resolve
60
i


conflicts and problems locally within the boundaries of the community or area which are generating them. The implementation and success of such a concept is predicated upon an adequate supply of inventory and baseline data as well as an agreement among the populace that passing problems on to their neighbors, either upstream or downstream, is an undesirable condition.
Among the Denver Regional Council of Governments, among its other functions, serves as both a repository of data and information, and a forum where local governments can meet and resolve conflicts and problems which affect each other.
Urban stormwater management is a complex structure of interrelated elements and as such is not without its problems.
Perhaps the msot significant problem is the gap between the management principle and objectives, and the actual results of those principles when they are transformed into realtiy. There is little basis for argument against the idea that stormwater management should be initiated at the regional scale with the appropriate objectives as guiding principles. But, the success of any large scale plan is essentially based in the efficiency and effectiveness of the subordinate elements working in general harmony toward the success of the regional plan. In the Valley Region the regional objectives have been more or less clearly stated. The objective is to manage stormwater and mitigate its adverse effects on the regional scale for the benefit of the environment within the defined region as well as the environment outside the defined region. Generally, this benefit has been defined and determined based on engineering and hydrologic principles. These principles have formed the regional scale framework within which the various subordinate elements (the communities) must function. The administrators of the regional scale principles have provided communities with information on various management structures, and how to establish a management


system that satisfies the objectives of the region. In spite of numerous agencies and a satisfactory regional scale objective, it appears that the gap between the individual communities needs and objectives and the regional scale principle has yet to be bridged.
One solution that would bridge the gap between the local and regional levels is to understand the needs, objectives, and principles of the regional management structure and have the ability to enter the local participating community, determine community needs, and provide a community system which satisfies both tiie goals and objectives of the region as well as respond to the needs of the community.
It would appear that the regional level administrators have established the desirable objectives and guidelines for regional scale runoff management and, to a point, have established the methodology by which these regional objectives are to be attained. The detention/retention method appears to be the general method of management and receives a great deal of regional level institutional support. Many of the suggestions for management methods proposed for runoff management at the community level involve the retention/detention devices. The major supply of data and information support the detention/retention method.
However, it is not to say that this is the optimal management method under all conditions and all situations. The selection of the management method at the community scale can and should respond to local needs over and above the the utilitarian and single purpose of drainage. The communities have been permitted this latitude under the organization of the regional system. In general, how communities resolve their runoff problems is left to them as long as the resolution satisfies the regional objectives. Typically it is the community’s responsibility to devise and
62


implement a stormwater management system which offers the most rewards for the community while fulfilling the objectives of the region.
Many communities lack the institutional resources to develop,
construct, enforce and maintain a runoff management system that
provides all the community rewards that the management system is
capable of providing. The concept/suggestion of multiple uses
for stormwater management systems is supported at the regional
level, but determining the optimum multiple uses for the runoff
management systems has been left to the individual communities.
The challenge for local communities is to match the needs and
desires of the community to.the stormwater management system's
capacity for fulfilling those defined needs and desires within
the regional framework. It is the local communities that know
their problems most intimately and the resolution of those
problems is dependent upon local conditions. It is for this
reason that a great deal of latitude in management response has
been established. "...the definition of the design situation
will specify a particular set of design objectives. These
objectives will state to what extent and in what manner the
f 21
runoff from a given site should be controlled."^ J
There are two fundamental elements of stormwater management which are of concern to the community when it begins to formulate a runoff management strategy that satisfies the regional plan. The first element is the runoff water which is generated as a result of development. The second element that must be examined is the land required for managing the runoff water. Figure 18 is a simplified flow diagram of stormwater management. It illustrates the typical process by which the runoff water can be managed.
63


EVAPORATION
PERCOLATION/
INFILTRATION
DEVELOPER'S
GENERAL
STORMWATER
MANAGEMENT
RESPONSIBILITIES
MANAGEMENT OF STORMWATER WHICH EXCEEDS
PREDEVELOPMENT AMOUNTS & RATES
ACCEPTANCE & MANAGEMENT OF STORMWATER ARRIVING ON THE DEVELOPMENT SITE
DETENTION
RETENTION USUALLY REQUIREES MEASURES TO COMPENSATE FOR EVAPORATION LOSSES
DISPOSAL
CONDUCTION/ DIVERSION TO MAJOR DRAINAGEWAY
DISPOSAL ON A DOWNSTREAM SITE AT PRESCRIBED AMT.S & RATES
UTILIZATION: DIRECTLY RELATED TO WATER QUALITY
MANAGED WATER FROM UPSTREAM DEVELOPMENTS
UNMANAGED WATER FROM DEVELOPMENTS CONSTRUCTED PRIOR TO "STORMWATER DRAINAGE DESIGN & CRITERIA"
UNMANAGED STORMWATER FROM UPSTREAM NATURAL AREAS
FIG. 18 SUMMARY FLOW CHART OF STORMWATER MANAGEMENT


The most fundamental decision in the entire process is the decision by the community to either adopt a management concept that utilizes their runoff water for community needs, or adopt a policy that regards runoff as a liability or waste byproduct of development which must be disposed of. If the decision is to utilize the runoff water, then decisions have to be made regarding what the optimal uses might be and then formulate a physical system which will support those uses. If the decision is reached that disposal of the water is the most viable alternative for the community, then the physical system will have to support the decision. A third option is to develop a system which disposes of the water for the present, but can be modified with little effort to utilize runoff water in the future. The complexity of the objective is a reflection of the complexity and detail to which the plan must be carried out and enforced. There are multiple use benefits for stormwater...what those multiple use benefits are and how they are obtained is determined by the forces acting on the community and site conditions.
The second element of stormwater management is the land required for managing runoff. There has been a tendency on the part of many communities to adopt suggestions made by the regional administrators and transform those suggestions into ordinances and resulting physical structures without examining the specific needs and conditions of the community. This practice has resulted in problem solutions that are out of context with the conditions of the site. In other words, communities are adopting measures which are not necessarily solutions to their problems. Such measures are implemented out of context to either the engineering goals of runoff management or the surrounding environment's needs. In order to alleviate this situation a clear understanding of the regional goals, community needs, and management is necessary.
65


One method by which communities can begin to formulate a runoff management strategy which will fulfill its community potential is illustrated in Figure 19.
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FIG. 19 PROCEDURE FOR DETERMINING THE APPROPRIATE MULTIPLE USES FOR RUNOFF MANAGEMENT SYSTEMS
The first step is an inventory process which is conducted to determine the social and natural forces acting on the community. The inventory phase should focus on determining the type of stormwater management system utilized in the community at the time of inventory. The system concept should be determined and an inventory of institutional support systems should be conducted to determine if the community has the institutional support to perpetuate the runoff management concept or future alternative
66


concepts. The next step is to determine if the in-place management system is an optimum system based on:
•The in-place runoff management system's ability to fulfill the objectives of the regional scale plan.
•The physiological, sucialcultural and institutional forces existing in and around the community.
Once the type of system used for managing stormwater has been determined, and an evaluation of the system's effectiveness has been made based on the physiological, sociocultural, and institutional support systems existing in the community the next step is to determine the conflicts that exist in the system.
An example of a system conflict might be that the community has established desirable goals and objectives that are beyond the capabilities of the city's institutional support system to implement or maintain. Such conflicts should be identified and resolved before proceeding to the next phase of plan development.
The next phase of determining a multiple use plan for runoff management is to develop a concept of multiple use which responds to the physiological, sociocultural, and institutional systems tolerance levels as determined in the preceeding phases. Once the optimum multiple use concept has been determined, the next step is to formulate designs for the physical environment that support the developed multi-use concept.
An important step in the process is to develop guidelines for future developments that will perpetuate the previously formulated concept. Ideally the guidelines will provide the community with a continuous visual theme and which will allow future


developments to be integrated into the management system without disruption of the proposed multi-use management system or the physical environment.
Every community is unique. The challenge to the designer/planner is to identify what physical, social, and institutional forces are acting on the specific community and utilize that information to formulate stormwater management systems which allow the community to develop their own individual system which results in the stormwater management element of the urban organism to be developed to its full potential.
« • •
68


REFERENCES
1. Webster's New Collegiate Dictionary. Springfield, Mass. 1975.
2. Roy F. Weston, Inc. Environmental Consultants-Designers.
Storm Water Management Design: A Manual of Proceedures and Guidelines. Kenneth C. Wiswall, Project Engineer, and K.S. Shumate, Ph.D., Project Manager. Prepared for the Maryland Department of Natural Resources.
Westchester, Pennsylvania;- Roy F. Weston, Inc. June, 1972.
3. Interview with Gary Mast, Principal Planner Water Resources
Management, and John T. Doerfer, Water Quality Planner,
Denver Regional Council of Governments, Denver, Co, 4 Nov. '82.
4. Urban Land Institute, National Association of Homebuilders,
and the American Society of Civil Engineers. Residential Storm Water Management', Objectives, Principles, & Design Considerations. New York, N.Y., Washington, D.C.: Urban Land Institute, National Association of Homebuilders, and the American Society of Civil Engineers, 1975.
5. U.S. Environmental Protection Agency. A Primer on Wastewater
Treatment. Pamphlet, Washington, D.C.: GPO, (A-107), 1975.
6. U.S. Environmental Protection Agency. Clean Water:
Understanding The Law. Pamphlet, Washington, D.C.:
GPO, ID No. 1978-260-880:69', 1978.
7. Wright-McLaughlin Engineers. Denver Regional Council of
Governments Urban Storm Drainage Criteria Manual. 2 vols. Denver, Colorado: Wright-McLaughlin, March, 1969.
8. Sheaffer, John R., Kenneth R. Wright, William C. Taggart, &
Ruth M. Wright. Urban Storm Drainage Management. New York, N.Y.: Marcel Dekker, Inc., 1982.
9. Novotny, Vladimir, Ph.D., P.E., and Gordon Chesters, Ph.D.,
D.Sc. Handbook of Nonpoint Pollution Sources and Management. New York, N.Y.: Van Nostrand Reinhold Co. 1981.
10. Development Research Associates, Inc. & Wallace, McHarg,
Roberts & Todd, Inc. Regional Transportation District Interim Report Ecology, np. nd.
11. Wright-McLaughlin Engineers, Engineering Consultants.
Technical Memorandum Factors Affecting the Cost of Erosion Control Planning. Prepared for: Denver Regional Council of Governments. Draft Document. June, 1982.


12. Wright Water Engineers. Technical Memorandum Costs to
Local Governments for Implementation of Erosion Control Programs. Prepared for: Denver Regional Council of Governments. Draft Document. July, 1982.
13. Wright-McLaughlin Engineers-Engineering Consultants.
Supplemental Report. Cost of Erosion Control Measures. Prepared for the Denver Regional Council of Governments. May, 1982.
14. Mast, Gary N. Managing Erosion and Sedimentation From
Construction Activities. Denver Colorado: Denver Regional Council of Governments. April, 1980.
15. Colorado Department of Highways. Erosion Control Manual.
Denver, Co:Colorado Dept, of Highways, 1978.
16. Michigan Department of Natural Resources. Michigan Soil
Erosion & Sedimentation Control Guidebook. Lansing, Mi: Michigan Department of Natural Resources. 1975.
17. U.S. Dept, of Agriculture, Soil Conservation Service.
A Guide for Erosion & Sediment Control in Urbanizing Areas of Colorado. Interim Guide. Denver, Co: Soil Conservation Service, nd.
18. Denver Regional Council of Governments. Summary First
Year Progress Report of the Denver Regional Urban Runoff Program. In cooperation with, U.S. Geographical Survey Subdistrict, Urban Drainage & Flood Control District, and the Member Governments of the Denver Regional Council of Governments. 1979.
19. Denver Regional Council of Governments. Summary Second
Year Progress Report of the Denver Regional Urban Runoff Program. In cooperation with, U.S. Geographical Survey Subdistirct, Urban Drainage & Flood Control District, and the Memeber Governments of the Denver Regional Council of Governments. August, 1981.
20. Colt, Jon L. Percolation Pits: Their Design, Construction,
Use, and Maintenance for Stormwater Disposal, Groundwater Recharge, and Surface Water Quality Protection in Adams County, Colorado. A brochure prepared by the Adams County Planning Department, Brighton, Co. nd.


21. Interview with Ben Urbonas, Chief of Master Planning Programs, Urban Flood and Drainage Control District, Denver, Colorado, Oct. '82.
22. Interview with Davis Holder. Professor, College of Design and
Planning, University of Colorado at Denver, 4 Nov. '82.
23. Jones, Jonathan E., and D. Earl Jones. "Interfacing
Considerations in Urban Detention Ponding." Presented at the August 1-6, 1982 Engineering foundation/ASCE Conference, "Planning, Design, Operation, and Maintenance of Stormwater Detention Facilities," at Henniker,
New Hampshire.
24. Whipple, William, jr. and Joseph V. Hunter. "Settlement
of Urban Runoff Pollution." Journal of the Water Pollution Control Federation. Vol. 53, No. 12, Dec., 1981, pp 1726-1731.
25. Laszewski, Edwin J. "Problems of Public Acceptance: Storm
Drainage Through Natural Watercourses." Published Proceedings of a research conference, "Urban Runoff Quantity & Quality." Held at Franklin Pierce College,
Rindge, New Hampshire, August 11-16, 1974. Published by the American Society of Civil Engineers.


IV. APPENDICES


ISSUES TO LANDSCAPE ARCHITECTS
Although each urbanizing site and situation promotes its own discrete set of runoff management problems, conflicts and issues have to be resolved at both the regional and local level, the three issues of overiding concern are:
• Best land use practices for communities
• Runoff water quality (nonpoint source pollution)
• Runoff water quantity (volume § rate)
This rank order list is not to suggest that the problems and challenges presented in one category are of less importance than those perpetrated in other categories.
Issues related to runoff quantity are, at present, of very high priority and of course have to be addressed and resolved. But, runoff quantity management by virtue of the fact that it consumes physical space in the environment becomes a land use problem. By this reasoning quantity, and to a lesser extent quality, management become elements of a larger issue... land use. The ranking then, is not an issue of subordination of priority resolution, but a ranking of elements within the organizational taxonomy.
Within this taxonomy, runoff quality management is ranked higher than quantity management. This ranking was based on the comparative progress of study between the two fields. Issues concerning runoff quantity are in a much more advanced position of study and clarification. Issues concerning runoff quality, by comparison, are not as advanced as those concerning quantity. The significance of the engineering and scientific "distance" between these two elements can be very dramatic. The issue of water quality is barely out of the scientific stage, whereas quantity


management is well into the engineering stage. It is unlikely that scientific advancements in quantity management will perpetrate, by comparison, a drastic change in land use and physical form. Quality issues however, present a relative unknown in the algebra of runoff management. Mitigation of water quality problems could easily result in significant changes in the land use and runoff management structures.
Ranking water quality above quantity is also a reflection of the need for baseline (pivotal decision) information. An example of this situation is; issues regarding runoff quantity can usually be quantified, and as a result of this quantification engineering and design criteria can be formulated. Conversely, water quality is still in the process of being defined.
Urban stormwater management is a complex and multifaceted field which contains all the elements that the landscape architect's methodologies and processes are designed to manage effectively. The field involves responding to multiple objectives, multiple and diverse stimuli from both the natural and social systems, diverse data and information which are both quantifiable and unquantifiable. The field must attempt to resolve generalized problems whose definitions are broad in scope and scale and comprised of numerous elements. The resolution of most management problems require the organization and synergization of data that have been extracted from a wide variety of focused and specific data categories regarding specialized facets of management which have been generated by the scientific and engineering methodologies.
At the present time the scientific and engineering communities
are feeling the pressure from the public sector to resolve broad
(251
based and multifaceted management problems. J It is at this
73


point that a dichotomy between the problem and the methodology utilized for its resolution begins to manifest itself. The scientific and engineering methodology is remarkably efficient when dealing with subjects that are quantifiable, well defined, and limited in the number of imputs. The scientific and engineering methodologies become less effective from a social and cultural environmental perspective, as variables increase in numbers and latitude.
The issue to landscape architects is to respond to the challenges of a diverse, often stochastic, and multifaceted problem utilizing the methodologies and processes unique to the profession to:
• Produce physical forms which are compatible with the natural and social environments.
• Produce the plans which will facilitate physical forms.
• Assist in determining the best management practices based on the regional requirements and the needs of the individual community.
The forms and practices must be responsive to the natural and social systems' tolerance levels and enhance the natural and social environments as they are defined by the residents of the community. It is the multiple purpose concept that will produce management systems which are appropriate to context and avoid systems which are single purposed, functionally utilitarian, and environmentally discordant.


HYPOTHESIS:
The formal hypothesis stated below will serve as a guide for the further investigation and response to the problems concerning urban stormwater management. The statement will be applied to the systems in and around the City of Lafayette, Colorado.
If runoff management systems in the Valley Region are designed for multiple uses based on social and natural system's tolerance levels; then social and natural environmental quality will be enhanced.


CASE STUDY, BUDGET, & TIME LINE
The case study for this project will be the City of Lafayette, Colorado. The primary area of the case study will be determined after an examination of the drainage conditions existing within Lafayette and the surrounding area has been completed. The case study at this point may be of necessity restricted to a single drainage basin located in the described area.
The project budget has not yet been determined
The timeline for the project is:
•Dec. 27-31: review drainage master plans for Lafayette and surrounding area
•Jan. 3-7:conduct area reconnaissance
•Jan. 10-14: declare case study area and begin sociological and natural systems inventory
•Jan. 17-21: develop trends and implications analysis
•Jan. 24-28: formalize background data
•Feb. 1-4: Declare and define problem statement
• Feb. 7-11: refine and formalize data and statements •Feb. 14-18: conduct feedback loop evaluations
• Feb. 21-March 11: begin rough draft document
• March 14-25: feedback response to rough draft of work completed to date
• March 28-31: prepare rough draft of final document
•April 1-15: formalize final document
The timeline presented above is subject to revision and adj ustment.


THESIS COMMITTEE
Daniel B. Young, Program Director, Landscape Architecture, College of Design and Planning, University of Colorado at Denver
Jerry Shapins, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver
Tom Haldeman, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver
Lori McMillan, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver
Jeffrey Pecka, ASLA, Landscape Architect and Environmental Planner, 99 Corona, Denver, Colorado 80218
Thomas A. Colbert, CPSS, CPAG, President T.A.C.A. Corporation


OPTIMIZING URBAN
STORMWATER MANAGEMENT FACILITIES THROUGH MULTIPLE USE
A TEST CASE:
CITY OF LAFAYETTE, COLORADO
JOHN V. GOEBEL
1675 BEOIVERE CIRCLE • LAFAYETTE • COLORADO 80026 • (303)666-6459
This case study was prepared and submitted as partial fulfillment of the requirements for a Master of Landscape Architecture Degree from the College of Design and Planning, University of Colorado at Denver.
Accepted:__________________________________
Daniel B. Young, Program Director
Date


THESIS COMMITTEE
Daniel B. Young
Program Director, Landscape Architecture, College of Design and Planning, University of Colorado at Denver.
Jerry Shapins
Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver.
Tom Haldeman
Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver.
Lori McMillan
Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver.
Jeffrey Pecka
Landscape Architect and Environmental Planner, 99 Corona, Denver, Colorado 80218
Thomas A. Colbert, CPSS,CPAG President T.A.C.A. Corporation
JURISDICTIONAL CONTACTS
Micheal Acimovic
Lafayette City Administrator, 201 East Simpson Street, Lafayette, Colorado 80026
Kathy Davis
Planning Director, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026
Tom Hoby
Director, Parks, Recreation, and Open Space, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026
Warren Williams
Director of Public Works, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026


TABLE OF CONTENTS
SECTION I Methodology Page 3
SECTION II Existing Conditions Page 8
SECTION III Suggested Multiple Uses Page 53
SECTION IV General Policies and Guidelines Page 76
Appendix 1 Data Base Page 101
Appendix 2 Reference Maps Page 103
Appendix 3 Lafayette Objectives Page 118


FIG. 1


EXECUTIVE SUMMARY
This booklet is part II of a two part project which applies the data and information generated in Part I (the research document) to the specific geographical area of Lafayette, Colorado.
This is a community scale design case study which proposes multiple uses for underdeveloped stormwater management facilities in the rapidly urbanizing City of Lafayette, Colorado. Lafayette is a city with a population of approximately 10,000 located fifteen miles North of the Denver City limits and eight miles East of the City of Boulder, Colorado (see Vicinity Map, fig. 1). Lafayette is one of the rapidly urbanizing areas comprising the front range urban corridor whose land use is in a transitional state' from primarily rural/agricultural to urban/suburban use.
The overall purpose of this study is to provide ideas and alternative uses for lands required for stormwater management which will enhance the quality of life for the community's residents and improve community image.
The document is intended to be used by those who are interested in the urban planning and design processes of the City of Lafayette, and by those persons who are interested in gaining additional community benefits from lands already in the public domain.
This case study recommends multiple use alternatives for underdeveloped stormwater management facilities. These multiple use alternatives are proposed as a means to elevate the awareness of stormwater management facilities as an underdeveloped community resource which can be further integrated into the urban design process. The final decision on what recommendations and alternatives are to be implemented and the priorities of implementation are left to the people who know the community; the residents of Lafayette.
This case study is divided into several sections as described below. •
• Section I is an explanation of the
methodology used throughout this project phase which provided the basis for study direction and decision making.


• Section II contains a brief description of the existing stormwater management conditions found in Lafayette. This section also includes a discussion of the selected multi-use concept, the selection of which was based upon the unique natural, sociocultural, and institutional conditions existing in and around the City of Lafayette.
• Section III describes a range of suggested multiple uses for stormwater management facilities which can be implemented based on identified community needs and the conditions which exist at specific stormwater management facility sites.
• Section IV suggests guidelines for developing multi-purpose stormwater management facilities. These guidelines are intended for use in areas that are in transition from rural land use to urban land use. However, many of the guidelines can be applied to areas already urbanized but contain underdeveloped stormwater management lands.
This case study is prepared with the point of view that stormwater drainage is a necessary element of the urban development process and that the lands required for drainage facilities can be developed and utilized to provide additional community benefits without radical alterations to either the management facilities themselves, or the institutional support systems which are responsible for the implementation, operation, and maintenance of public spaces and facilities.
A portion of the expenses for materials and reproduction of this case study have been funded by the City of Lafayette, Colorado.


TRAIL JUNCTION/ACTIVITY NODE
SECTION I


INVENTORY DETERMINE THE TYPE OF STORMWATER MANAGEMENT SYSTEM
UTILIZED IN THE PROJECT AREA
• DETERMINE SYSTEM CONCEPT
• EXAMINE INSTITUTIONAL ORGANIZATION & EXTENT OF SUPPORT
ANALYS,S DETERMINE THE APPROPRIATENESS OF THE IN-PLACE MANAGEMENT
SYSTEM BASED ON THE FOLLOWING CONDITIONS:
• PHYSIOLOGICAL
• SOCIOCULTURAL
• INSTITUTIONAL
RESPONSE IDENTIFY & RESOLVE ANY SYSTEM POLICY CONFLICTS
DETERMINE THE OPTIMUM MULTI-USE CONCEPTS BASED ON THE TOLERANCE LEVELS OF THE FOLLOWING CONDITIONS:
• PHYSIOLOGICAL
• SOCIOCULTURAL
• INSTITUTIONAL
GENERATE FORM RESPONSES FOR THE BUILT ENVIRONMENT
GENERATE GUIDELINES FOR FUTURE DEVELOPMENTS WHICH WILL:
• PERPETUATE THE CONCEPT/CONCEPTS GENERATED ABOVE
• PROVIDE A CITY-WIDE CONTINUITY OF DESIGN THEME
• FACILITATE THE INTEGRATION OF FUTURE DEVELOPMENT DRAINAGE SYSTEMS
FIG. 2 PROJECT PROCEDURE


OBJECTIVE
The objective of this case study is to develop a multiple use program for the lands required to manage stormwater runoff which will enhance both the community image of Lafayette and the quality of life for its residents. The determinants on which the multi-use program is to be based are as follows:
• NATURAL ENVIRONMENT: The opportunities and constraints of the physical environment in and around the City of Lafayette.
• SOCIOCULTURAL ENVIRONMENT: The defined goals and objectives of the residents of Lafayette.
• INSTITUTIONAL ENVIRONMENT: The capabil-ities of the existing institutional support systems such as the city staff, as well as the capabilities of the various agencies and systems which have been created to assist local governments with community development.
• • •
GOAL
The project goal is to produce a program of multiple uses for stormwater management facilities that are compatible with the plans, agencies, and systems which exist in and around the City of Lafayette, and to produce a program which can respond to future growth impacts in a smooth and efficient manner.


METHODOLOGY
The methodology used in the preparation of this study involved the following phases.
• INVENTORY: An inventory of existing conditions in and around the City of Lafayette.
• ANALYSIS: An analysis and interpretation of the data and information collected in the inventory phase.
• RESPONSE: The formulation of design suggestions and guidelines that are compatible with the local conditions as they are defined in the previous two phases.
The specific procedure that was followed during the preparation of this case study is outlined in figure #2. As can be determined from the outline, a specific focus of the inventory and data gathering phase was the determination of the type of stormwater management system that is currently being used in the City of Lafayette, and the extent of the institutional support behind that management concept. These points; management concept and the extent of institutional support, were examined and analyzed in addition to the natural and social forces acting on the City of Lafayette as they are defined in the documents listed in appendix #1.
As a part of the analysis phase, an evaluation of the appropriateness of the in-place stormwater management system was made based on the natural and social environments in and around Lafayette as well as the capabilitie of the institutional system supporting the existing management policies. This evaluation was made after the data gathering and inventory phases were concluded.
The next phase of the procedure identified and resolved, at the policy level, any system conflicts that were disclosed as a result of the data gathering and inventory phase. In the case of Lafayette the system conflicts and suggested resolutions are mainly policy issues and as such do not present physical obstacles to implementing multiple uses for stormwater management facilities.


The response phase of the procedure, the final phase, involved the following three steps.
• The formulation of an optimum multi-use concept which was tailored to the capabilities and acceptability levels of the natural, social, and institutional environments in Lafayette.
• The development of plans for physical forms for the built environment which were directed by the concepts formulated in the previous step.
• The formulation of guidelines for future developments which will perpetuate the concept formulated in step 1, provide a continuity of a design theme for the city, and facilitate the integration of runoff management systems and facilities which will result from future development.
In keeping with the goal of producing a multi-use program for stormwater management facilities that would be compatible with both existing and future plans for the City of Lafayette, the inventory phase included the following tasks:
• A complete review of all the planning studies produced by the City of Lafayette. A complete listing of these documents can be found in appendix 1. •
• Information exchanges with the following parties:
City Administrator City Planning Director City Parks, Recreation, and Open Space Director
City Public Works Director


Visual inspections of the following sites and facilities:
• Areas of Lafayette which are currently being used to manage stormwater.
• Existing park facilities in Lafayette
• Land areas in Lafayette that are designated for development as future park spaces
• Areas in and around Lafayette that are designated as open space
• Sites located in neighboring communities where stormwater management lands have been developed for additional community uses
A review of planning documents for areas adjacent to the City of Lafayette.


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DRAINAGE BASIN ADAPTED FOR MULTIPLE USE
SECTION II


STORMWATER MANAGEMENT IN LAFAYETTE
The type of stormwater management system used in Lafayette at the present time is directed by two major documents which are intended to work in conjunction with each other. These two documents are:
1. "City of Lafayette and Surrounding
Unincorporated Areas of Boulder County, Colorado Storm Drainage Design and Technical Criteria."
2. "Major basinwide Planning City of
Lafayette/Boulder County Phase B Development of Preliminary Plan."
Together, these two documents establish a management policy of collecting, detaining, and conveying stormwater runoff through a system of open channels and detention facilities. From an analysis point of view, the proposed drainage system which will result from implementing the policies and procedures defined in the two documents is, in general, appropriate based on Lafayette's natural, social, and institutional support systems. The physical facilities and structures that will result when the Phase B Plan is implemented, combined with the policies and resulting forms generated by the Technical Criteria, offer unique opportunities for multiple uses.
Although the Technical Criteria and Phase B preliminary Plan are intended to work in conjunction with each other, they are two different documents. The Technical Criteria document is, in general, a policy document, whereas the Phase B development Plan is a city-wide physical design plan for major drainageways. At the present time the Technical Criteria is being implemented at the policy level and the status of the Phase B Development Plan is in the preliminary phases of implementation. The current planning status of the Phase B plan offers Lafayette the unique opportunity to incorporate multiuse concepts with the physical drainage designs in the preconstruction phase.
The expedient implementation of the Phase B Development Plan should be regarded as a high priority project by the City of Lafayette. This evaluation is based on the


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. RUNOFF: URBANIZATION & LAND USE PART 1 RESEARCH

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RUNOFF: URBANIZATION & LAND USE PART 1: RESEARCH PREPARED BY JOHN GOEBEL This thesis research is submitted as partial fulfillment of the requirements for a Master of Landscape Architecture Degree at the University of Colorado at Denver, College of Design & Planning, Graduate Program of Lands e Architecture. Accepted: 14-) 10R3' Date

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CONTENTS PREFACE I. INTRODUCTION URBAN STORMWATER MANAGEMENT RESEARCH SCOPE & SCALE PROJECT LOCATION II. BACKGROUND THE HYDROLOGIC CYCLE HISTORIC PERSPECTIVE URBAN RUNOFF METHODS THE SOCIAL SYSTEM Ill. INTERPRETATION ii 1 5 7 9 13 17 28 40 Il\1PLICATIONS OF TRENDS & PRACTICES 4 7 CONCLUSIONS 59 REFERENCES 69 IV. APPENDICES ISSUES TO LANDSCAPE ARCHITECTS HYPOTHESIS CASE STUDY, BUDGET, & TIME LINE THESIS COMMITTEE 72 75 76 77 • I

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PREFACE MOVING TOWARD A HIGHER QUALITY OF LIFE The specific purpose of this study is to assist communities in deriving additional benefits from their stormwater management systems. The method by which these additional benefits are to be gained is by proposing multiple purposes and uses for stormwater and the lands required for its management. These multiple purposes and uses will be based on the natural, social, and institutional conditions existing within and around the community seeking to upgrade their system. This study will be of value if the results enhance the services and opportunities a particular urban environment affords its residents (i.e. enhances the reasons why people reside in a particular community), and enhances these attributes in a manner that elevates the visual and aesthetic features of outdoor spaces in a practical and feasible way. The general purpose of this study is to enhance the attributes of urban life and to elevate the visual and aesthetic features of urban life and to elevate the visual and aesthetic features of outdoor urban spaces by increasing the efficiency of the urban organism. The heal thy urban organism, or community, is comprised of many elements all working in harmony to provide its residents with the services and lifestyle its residents desire. The residents, through democratic action, determine the services and the kind of lifestyle they want their community to provide and then adjust the various which make up the urban organism so that the organism will furnish the services and particular lifestyle desired by the majority based on natural, social, and economic limitations and opportunities. It follows then, that as residents of a community we are at once producers and consumers of our urban environment. As producers and consumers it is to •• II.

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• • • Ill our benefit to make sure that we receive the maximum benefits from each working element of the urban organism. Each element of the organism must fulfill its potential efficiently and economically without adversely affecting the harmony of total organism. Stormwater management is an element of the urban organism which, in many communities, has not yet been developed to its full potential. In many developed and developing areas stormwater management alternatives have not been fully examined or evaluated in an effort to determine if the existing and future management methods are supplying as much service to the community as possible. Stormwater and the lands required to it can provide additional benefits to a community and respond to additional community needs beyond the singular need of drainage. Additional community benefits can be gained by most cities through implementing a multi-purpose stormwater management strategy. This simply means that the stormwater management element of the urban organism must respond to other community needs as well as the single purposed and utilitarian function of draining an area of occassional stormwater. If a community wishes to increase the efficiency of the urban organism, then stormwater management must serve additional community needs as well as drainage. The challenge is to determine the best additional purposes and uses for this element of the organism based on the conditions existing in and around the community and within the framework of water law. • • •

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I L z 0 I(.) :::> 0 0 a: 1z • I r I I -

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URBAN STORMWATER MANAGEMENT RESEARCH & CASE STUDY This document is the conclusion of the first phase of a two phase project. Phase I is a project research phase which is a general overview of urban stormwater principles and practices. Phase II of the project is a case study which applies the information and conclusions generated in Phase I to a specific geographical location. The case study area selected for this project is the urbanizing community of Lafayette, Colorado. STOAMWATER MANAGEMENT & THE URBAN ORGANISM A dictionary definition of an organism is; "A complex structure of interdependent and subordinate elements whose relations and properties are largely determined by their function in the whole."(l) A vital element of the urban organism is stormwater management. If this element of the urban organism is not functioning properly then it reduces the efficiency (or health) of the entire urban organism. Urban stormwater management is a complex structure of interrelated parts which can be confusing to those who are not a part of the professional community which deal specifically with runoff. This research was initiated on the presumption that many stormwater management facilities may be functioning adequately f rom a strictly engineering principle and theory point of view, but from the broader perspective of urban design both the management structures and the land required to mana g e runoff are community resources which are not developed to their full potential. In most situations, communities can gain additional benefits from the stormwater management element of the urban organism. Research 1

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2 conducted for this project did not disprove the initial presumption. However, the final determination of whether or not stormwater management if fulfilli ng its potential within the urban organism is left to those who direct the form, function, and visual appearance of public spaces in our communities ... the residents. This research document is a general overview of urban stormwater management principles and practices and is presented to those who wish to elevate their knowledge in this topic area. Efforts for this phase of the project were directed toward providing a basic understanding of urban stormwater management for those who wish to participate more effectively in the following urban processes: • The process of evaluating the existing or proposed stormwater management element of the urban organism to determine if the element is providing the community with all the benefits that it is capable of providing. • The development of methods and practices which would determine the optimum additional benefits which could be gained from the management element if it is determined that these facilities are not fulfilling their potential. Increased stormwater runoff is a problem directly related to urbanization. (Z) The problem of increased runoff is general:y resolved in their outdoor environment. Generally, the prob:em resolution results in physical forms which become a prominent

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part of the visual landscape. Structures and spaces required for managing runoff which are a part of the urban landscape and subject to view by the public at large become visual messages which publicize the amount of pride the residents have in their community as well as providing visual evidence regarding the efficiency or health of the urban organism. SUMMARY: • This project is a two phase project. • Phase I is the project research phase which examines the principles and practices of urban stormwater management • Phase II is a case study wherein the knowledge generated in the first phase is applied to a specific site or location. • The case study location is the urbanizing of Lafayette, Colorado. •A community is an organism comprised of many interdependent elements. • A vi tal element of the urban organism is stormwater management. • In many instances the urban stormwater management element of the urban organism has not been develcped to its full potential. The community can gain added benefits from this vital element. 3

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4 • The information generated for this project research phase is an overview of urban stormwater management principles and practices. • The research is presented to those who wish to elevate their knowledge of management practices and principles and for those who wish to participate more effectively in evaluating the benefits the community is gaining from an existing or proposed stormwater management system as well as determining the optimal additional benefits the management element can provide. •Managing stormwater is a prominent feature in the visual environment. •The visual forms created by managing stormwater are messages to the public at large which communicate the amount of pride residents have in their community as well as visual evidence regarding the general social health of the community. • • •

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RESEARCH SCOPE & SCALE BETWEEN FLOOD CON'TltOL A PERCOLAnoN PITS For the purposes of this study a distinction is made between flood control and stormwater management. A quote from; Stormwater Management and Design: A Manual of Procedures And Guidelines, will serve as the line of definition between the two subjects of flood control and stormwater management. "The distinction between stoYmwater management and flood control often becomes an issue, ... this is essentially a matter of degree, with flooding being associated with the more severe runoff situation. The context of stormwater management may be broadened to include flood control according to personal interpretation of the basic principles of runoff control."(Z) For the purposes of this study, urban stormwater runoff is considered a subordinate but related element of a higher order system which is the flow of water as a consequence of climatological activities over land 3.reas. Urban stormwater runoff is an element within the larger system with its own set of issues, constraints, and opportunities which are d istinct but related to other elements of both larger and smaller scale. Figure 1 graphically illustrates the project scope and scale. The element of stormwater runoff for example is a subordinate element of flood control, but superior to mitigation devices such as percolation pits. 5

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6 FIG. 1 PROJECT SCOPE & SCALE WATER QUALITYBETWEEN POLLUTION A PCB'S A hierarchy of scale has been established for the topic of stormwater runoff quality which is similar to the hierarchy established for the topic of stormwater runoff. The discussion of water quality in this document falls between the larger element of water pollution in general and the subordinate element of PCB contamination. • • •

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PROJECT LOCATION THE FRONT RANGE URBAN CORRIDOR The specific geographical area selected for applied study is known as the Valley Region which is a subordinate region within the urbanizing belt extending in a north, south direction along the base of the eastern slope of the Colorado Rocky Mountains. This urbanizing belt is referred to locc:.lly as, "The Front Range Urban Corridor." The Valley Region is a sub-region located within the geopolitical boundaries which define the Denver Regional Council of Governments. Figure 2 illustrates the contextual location of the Valley Region within the State of Colorado. Figure 3 illustrates the contextual location of the Valley Region within the boundaries of the Denver Regional Council of Governments. The Valley Region of Colorado is presently experiencing the greatest amount of urban growth in the state. ( 2 ) This urbanizing trend is expected to continue for at least the next decade. Land use in this area is changing from primarily agrarian (farming and ranching) to urban and suburban use at a rate commensurate with urban development. This region shares many characteristics with other regions within the front range urban corridor which permits many of the research conclusions and much of the research data to be applied to other areas of the front range. • • • 7

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Fig. 2 at right illustrates the location of the Denver Regional Council of Governments as it relates to the State of Colorado. Fig. 3 below, illustrates the location of the Valley Region as it relates to the Denver Regional Council of Governments. 8 FIG. 2 'i PLAINS ,_ ' . --'--=:- • ' . ...___ '"' • • • FIG. 3 STUDY AREA & REGIONAL DEVELOPMENT FRAMEWORK .Ill DENVER CBD Of DENVER 0 AREAS • RURAl !OWN CENTER A MOUNTAIN DEVELOPMENT AREAS

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r L c z ::::> 0 0: (..) <( m • f _LI -

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THE HYDROLOGIC CYCLE URBANIZATION I INCREASED RUNOFF In areas where development has not yet occured, stormwater management is provided by nature. The cycle begins with precipitation (rainfall in this example). A portion of the water is intercepted in the vegetative cover growing on the site and remains on the leaves, branches, and stems and evaporates, never coming in contact with the ground. Some of the water is absorbed into the ground near the surface and is utilized by plants for food and then ultimately returned to the atmosphere through the process of transpiration. Some water infiltrates deep into the ground and replenishes the groundwater supply. A portion of the remaining water collects in depressions in the land surface and remains in place. The water that arrives on the site after all the above storage devices have been used to their capacity flows overland. The flow generally begins as sheet flow, then collects and flows in rivulets, accumulating in both volume and speed as it flows down the watershed through drainageways, streams, and rivers to the ocean where it begins the cycle again. Figure 4 is a simplified illustration of the hydrologic cycle. Figure 5 is a diagram of the hydrologic cycle which illustrates how the hydrologic cycle works schematically. Urbanization of undeveloped land significantly affects the drainage patterns and processes that existed prior to development. Typical site development processes significantly impact the drainage system that existed prior to site development. The major impacts to the drainage system are described below: 9

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10 II I : II EVAPORATION EVAPORATION I I ! I I l I I l evaporation I I 1 & II evapotransp, ration II FIG. 4 HYDROLOGIC RAIN (SNOWMELT) EV .C.PORA TT ON ...., "' SURFACE RUNOFF < 0:: 0 >-V> --, :z: INTER FLOW I "" ...., I "" >-SOIL I ., WATER--l ... MOVEMENT 3 C) I -' u... I :>: FLOW FROM SPRINGS & c( ...., 0:: I >-V> GEOLGGICAL WATER LOSS __ J FIG. 5 SCHEMAnC DIAGRAM OF WATERSHED HYDROLOGIC MODEL

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• Development typically increases the impervious area of a site which reduces the amount of water that was previously absorbed by the soil. •Vegetative cover is generally reduced which increases the amount of water reaching the ground. • The surface topography is altered which generally reduces the depression storage capacity of the site with a commensurate increase in overland flow volumes. The cumulative result of these adjustments to the predevelopment drainage system (providing compensating adjustments are not made to the site) are: •Development causes a significant change in the volume of overland flow. • Development causes a significant change 1n the rate of overland flow. "Urbanization has requ2.red new drainage systems because man was both unwilling to suffer the inconvenience where it could be avoided and because he would not tolerate the loss of life or property."(4 ) • • • 11

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12 SUMMARY: •Development disrupts the drainage systems existing prior to development. • Development significantly increases the volume and rate of stormwater runoff. • Increased runoff volumes and accelerated runoff rates resulting from development must be managed to suit the needs of man such as reduce periodic inundation, and mitigate stream bank erosion, sedimentation, and etc. • • •

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HISTORIC PERSPECTIVE A CHANGE IN RUNOFF MANAGEMENT PRINCIPLES Prior to 1945, most urban development involved small parcels of land. ( 4 ) Stormwater runoff was easily managed using the then prevalent management principle of rapid downstream disposal of surface water. Rapid downstream disposal (the restoration of maximum convenience in the shortest possible period of time by removing stormwater runoff as quickly as possible) was a viable disposal method as long as urbanization was slow and involved relatively small parcels of land. Slow development combined with development on a relatively small scale made the cumulative impacts of rapid downstream disposal difficult to assess. The impacts were adversely affecting the drainage system on the large scale, but the impacts were relatively minor and went unnoticed because of the small scale of development. As illustrated in Figure 6, development began to be conducted on a much larger and more rapid scale in the post 1945 period. It was at this point in time that a more vigorous stormwater management program became necessary because urbanization and its consequent disruption of the existing drainage systems resulted in significant increases in runoff volumes and runoff rates. Upstream developments were passing their increased quantities of runoff to their neighbors located downstream. Rapid disposal became a workable principle in the upper and middle reaches of a watershed, but it created an unbalanced system which increased the hazard and risk to those who resided in the lower reaches of the watershed. ( 4 ) A common practice for managing stormwater in the pre 1945 period was the combined stormwater and sanitary sewer system. The combined sewer system accepted both sanitary sewage and storm-13

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14 Fig. 6: In the post 1945 period, development occurred on a larger scale and at an increased rate. It was at this time that runoff issues had to be addressed with a degree of complexity commensurate with the scale of development and its impacts. 11100 -FIG. 6 RELATIVE GROWTH & IMPACTS water in the same conveyance structures. The conveyance structures usually terminated at a sewage treatment facility (see Figure 7). When a storm occured the increased water load on the system would generally overload the treatment facility. To avoid overloading the facility the mixed sanitary and stormwater influant was bypassed around the treatment facility and discharged without treatment into the watercourse serving the treatment facility. This practice caused high levels of pollution in streams serving urban areas. (S) In the late 1960's and early '7Qls a combination of increased problem awareness and pressure from environmental groups prompted federal legislation which dealt with the problems of water pollution through various federal acts. A federal act 111110'8 that had a great impact on the combined sewer system was the Federal Water Pollution Control Act and its amendments (PL 92-500) of 1972. Among other programs, this law established a national permit program for discharges from all point sources -industrial, municipal, commercial, agricultural, and other facilities that release pollutants through pipes and sewers. ( 6 ) Since most of

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the combined sewer systems discharged through a pipe into a watercourse the implications of this law were to either segregate the sewerage systems or construct treatment facilities that would have the capacity to treat both sanitary sewage and stormwater runoff to a quality level that would satisfy federal discharge criteria. The costs of constructing sewage treatment facilities with enough capacity to treat both sanitary sewage and stormwater began to exceed the benefit of this practice, particulary when the facility would be used at or near capacity only periodically during storms. The increased hazards posed to downstream residents combined with the implications of the pollution control regulations The system illustrated (right) was the general management system up until the 1970's when it became apparent that such practices were degrading the environment beyond acceptable social and natural tolerance levels. -15

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16 prompted a reexamination of stormwater management practices. A new stormwater management philosophy emerged; restrict the flow of stormwater leaving a development site to the levels of flow that existed on the site prior to its development. The new philosophy represents a nearly complete reversal of the past management practice of rapid downstream disposal and lays the foundation for a variety of stormwater management structures. SUMMARY: • A significant change in stormwater management practices emerged in the mid to late '40's ... from rapid downstream disposal to restricting stormwater flows leaving developed sites to their predeveloped levels. • The change in stormwater management practices was prompted by; increased hazards to residents in the lower reaches of a watershed, and the segregation of sewage systems. • • •

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URBAN RUNOFF RUNOFF: A SPACE ALLOCATION PROBLEM There are a number of related issues surrounding the management of stormwater. The major issues can generally be classified into three categories: • Stormwater quantity and quantity related to time. • Stormwater quality (pollution) (discussed in the following section) • Land requried for stormwater management. The Urban Storm Drainage Criteria Manual states, ''Drainage is a space allocation problem."(?) The following two paragraphs are quoted directly from the Urban Storm Drainage Criteria Manual: ''The volume of water present at a given point in time in an urban region cannot be compressed or diminished. It is a space demand which must be considered in the planning process. Because the space required canr.ot be altered, choice is limited to location considerations. Where should the water be temporarily sto:-ed?" "Effects on Other Sub-Systems. Channels and storm sewers serve both a conveyance and storage function. When a channel is planned as a conveyance feature, it requires an outlet ---available downstream storage space. When considered as a space demand, 17

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18 the provision of adequate drainage becomes a competing use for space along with other land uses. If adequate provision is not made in a land use plan for the drainage demand, stormwater runoff will conflict with other land uses and will result in water damages and will impair or even disrupt the functioning of other systems." The implication of the first paragraph is that the amount of stormwater existing in an urban region is fixed based upon the extent of the development and the amount of precipitation. This amount of stormwater will exist whether or not it is planned for ormanaged. The only logical management alternative for planners is where this water is to be stored. It is the location function which can be most effectively manipulated in the management process. The second paragraph addresses the question of the land for stormwater management and other competing uses for that land required for management. This paragraph illustrates the importance of including stormwater management as an element in land use and community planning. (S) An aspect of runoff that has not been addressed to this point is that runoff is typically the result of a storm event. It is a fact of nature that storms are periodic and not constant which indicates that the land required for runoff management will only be used for its primary intent of management periodically whenever storm events occur. The remainder of the time (between storm events) the land required for management will not be used for its primary intent. More simply, the land required fer management must always exist, but the land will only be utilized for its management function during design storm events.

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ILl " a: c % CJ Cl) Q Post Development Runoff Pre-Development Runoff TIME 1. Increased Peak Discharge 2. Reduced Time To Peak 3. Increased Runoff Volume (2) FIG. h EFFECTS OF DEVELOPMENT ON HYDROLOGIC RESPONSE Figure 7A illustrates the runoff which must be managed as a consequence of development. The shaded area under the curve represents that runoff which is a result of development without runoff mitigation measures. The impacts of post development runoff are listed below the illustration. It is the mitigation of the following impacts which form the foundation of contemporary stormwater management practices: •Increased peak discharge •Shortened time to peak discharge • Increased runoff volume 19

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20 HYDROSYSTEM ELEMENTS PRECIPITATION INFILTRATION INTERCEPTI9N TRANSPIRATION EVAPORATION OVERLAND FLOW GROUND WATER FLOW CHANNEL FLOW SURFACE STORAGE WATER TABLE > > !::: Ut-U... tu. z a.. co >UJZ UJ::> t-ot-::> ZCll Z::>UJ ez::u. UJQ..<.!) UJO t-Z UJZZ UJ::> 00: Figure 8 is a matrix which illustrates the relationships between the elements of the hydrosystem, those elements which are a function of runoff quantity, and the elements of the hydrosystem which are typically manipulated to manage stormwater runoff. • • •

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RUNOFF WATER QUALITY EROSION, SEDIMENTATION, a NON POINT SOURCE POLLUTION Runoff water quality is a relatively new issue in runoff management. Runoff water quality became an issue of environmental concern in the late 1960's and early '70's. The Federal Water Pollution Control Act and its amendments which were enacted into law in the first half of the '70's mandates that, " . . . to the extent practicable, waste treatment technology shall be on an area wide basis and provide control or treatment of all point and nonpoint sources of pollution."(6 ) The United States Environmental Protection Agency definitions of point and nonpoint source pollution are: ( 6 ) Point Source: "When wastewater is discharged through pipes or sewers it is called a 'point source,' and this form of pollution is controlled through a national permit system which issues individual permits prescribing the types and amounts of pollutants that a municipality or an industry can discharge into waterways." Nonpoint Sources: " ... pollution that is carried over land by rainwater or melting snow or which seeps through the earth and enters waterways in a general manner not through a pipe or sewer." 21

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22 Figure 9 illustrates the differences between point and nonpoint pollution sources. In their book, Handbook of Nonpoint Pollution, Novotny and Chesters propose the following as a summary of 9 ) differences between point and nonpoint pollution sources( Point Sources Fairly steady flow and quality. Variability ranges less than one order of magn1tude . The most severe impact is during low summer periods Enters receiving water at identifiable points Primary parameters of interest: BOD, dissolved oxygen, nutrients, and suspended solids. Nonooint Sources Highly dynamic in random, intermittP.nt intervals. Variability often ranges more than several orders of magnitude. The most severe impact during or following a storm event. Point of often cannot be identified or defined. Primary parameters of interest: Sediment, nutrients, toxic substances, pH, and dissolved oxygen. FIG. II A 0#' POINT a -T P0LU1T10N SOURCES Within the Valley Region, and the Denver Regional Council of Governments' boundaries, studies are now being conducted regarding water quality. At the present time the data collection phase of the study is in the final stages. A publication of the data is projected for January, 1983. These data will be useful for determining baselines and trends as well as periodicity of pollution elements contained in stormwater. A subject of significant importance is the determination of adverse environmental impact on streams and waterways; the extent of impact, and if runoff pollution even causes any significant adverse impacts. According to the Denver Regional Council of Governments however, it will be approximately another ten years

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before mitigation systems will begin to be put in place if it is determined that they are necessary. ( 3 ) This time figure depends upon the emphasis and initiative regarding runoff water quality management remaining the same as it is at the present time. On a larger scale, not specific to the Valley Region, the literature reviewed for this document demonstrates that a sizable amount of study has been conducted in the area of stormwater runoff nonpoint source pollution. Study is currently being vigorously conducted in the following categories: •Surface water problems •Hydrologic considerations as related to nonpoint pollution •Runoff water pollution from the atmosphere •Erosion and sedimentation • Interaction of pollutants with soils •Groundwater pollution •Pollution from impervious urban areas •Nonpoint pollution simulation models •Land use and nonpoint pollution •Management practices of nonpoint pollution control • Planning for nonpoint pollution control 23

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A study conducted for the Regional Transportation District has concluded that most of the aquifer recharge areas underlying the major water courses in the Valley Region are presently contaminated. If runoff water quality is not improved it could threaten the use of these aquifers as potable water supply sources. (lO) An aspect of stormwater management that is being investigated and is prompting action in the Valley Region is erosion and sediment control. Draft documents which will comprise the Denver Regional Council of Governments' best management practices manual deliniate the costs of erosion control and sedimentation mitigation. (ll) (lZ)(l3)(l4 ) Additional information on methods and practices of erosion control and sedimentation management can be found throughout the literature. Consequences of erosion and sedimentation include; soil loss, watercourse turbidity, modification of hydraulic profiles of runoff conveyance systems, chemical transport, siltaticn, and etc. (lS)(l6)(l?) The problem is generally being addressed at the site of construction or disturbance. Areas that are not being disturbed by development activities often contribute to the sedimentation problem. Management techniques used in undeveloped areas usually attempt to reduce runoff velocity so that particle erosion is minimized. Land use and management practices are also being used to promote vegetative cover which reduces runoff velocity and consequent particle transport. The Environmental Protection Agency has prepared a set of categories for which selected water quality criteria have been established. Figure 10 lists selected water quality criteria for surface waters. Figure 11 is an outline of factors which determine pollutional loadings from urban areas. The criteria 24

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lS generated from an organization of categories which are listed below; • Problems with sediment • Dissolved oxygen and biodegradable organics •Nutrient contribution and eutrophication •Toxic chemicals and metals ,., FIG. 10 I!LI!C'T1!!D SUIFACI WA 181 QUALITY CIIITPIA Filh alld Plimuy (Contact) aDd ............ A.ecra.tion WumWacer COld Wate-r pH 6.5-8.3 6-S T oral alkalini 1 y (ml CaC03/Uter) >20 Turbidity Sca:hi disk (m) >1.2 Jackson Units <50 Max. tempen.ture ("C) <30 Max. tempenNre i:lxygen (mtJlitcr} >5 Total pll osphorus ("llititer) <100" Coliform medbn MPN (NoJIOO ml) Fecal colifomts (No./100 ml) <2001 •Normal pH nnl! should nol be altered by more than 0.1 pH units. bfor l akes < 1.6 C. cPeriod June-AuiJwC. 6-9 >20 <10 <20 <2.8. >6 <1008 ttbrine 6.7-8 .51 <0.81: <2.2d <10%of rut ural varirations <70' dPeriod September-May. and hunuinJ. MaxUnum of tO% of URll)les not to ucccd MPN of 2)0/11)0 ml for five tbe IMax.imum .,r tO';b of samples not t::t exceed 400/100 ml durintany lO-day penod. 25

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26 THE FOLLOWING LIST OF FACTORS IS PROPOSED BY NOVOTNY & CHESTERS IN THEIR BOOK: HANDBOOK OF NONPOINT POLLUTION. "A list of factors that determine pollut ional load1ngs fror.1 areal sources and their relation to land uses are listed as follows." 1. Factors strongly affecting pollution generation and correlated closely with land u;es: a. Population density. b . Atmospheric fallout. c. Degree of impervious area usually correlated with population density. d. Vegetation cover. e. Street litter accumulation rates. f. Traffic density. g. Curb density and height. h. Street cleaning practices. i. Pollution conveyance systems 2. Factors strongly affecting pollution generation but correlated poorly with land uses: a . Street surface conditions. b . Degree of impervious directly connected to a channel. c . Delivery ratio. d . Surface storage. e. Organic and nutrient content of soils. 3. Factors affecting pollution generation but to land uses : a. Meteorologic factors. b. Soil characteristics and composition. c. Permeability. d . Slope. e. Geographical factors. Many of the conflicts between mitigation measures for water quantity and water quality have not yet been clearly identified. An example of how solving a runoff quantity problem can conflict with the mitigation of water quality is the common curb and gutter. The curb and gutter are usually implemented to direct/ channel runoff water. However, these same structures can become catchments which collect sediments and pollutants. It has been observed and documented that 80% of street refuse can be found within 5.9 inches of the curb and over 95% of all street refuse will be within 3 feet of the curb structure. ( 9 ) When a storm generates enough runoff to begin flow along the gutter, the pollution is carried by the flow and deposited in the catchment/watercourse.

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Water quality is a definite issue in urban stormwater management and the environment. (lS)(lg) Data in this area however, are not as complete as the data available for stormwater runoff quantity. Although the objectives and goals of managing runoff quantity may at times be elusive, the objectives of runoff quality management are even less clearly defined at this point in time. There is one issue that is conclusive; the designer/ planner will have another level of complexity to deal with in urban stormwater management, and that is stormwater quality. Implicit in this discussion of runoff water quality is the possibility of designed obsolesence. If the designer today does not think to the future when designing management structures and devices for present use, it is very likely the costs of retrofitting present structures in the future to improve water quality will be very costly. • • • 27

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28 MANAGEMENT METHODS A RUNOFF MANAGEMENT PRIMER The Urban Stormwater Criteria Manual prepared for the Denver Regional Council of Governments defines two distinct storm events and their associated drainage systems. These events are defined as the major and initial events and related systems. They are defined as follows: "Initial Drainage System: That storm drainage system which is used for the collecting, transporting, and of snowmelt, miscellaneous minor flows, and storm runoff up to the capacity of the system. The capacity should be equal to the maximum rate of runoff to be expected from the initial design storm which may have a frequency occurrence of once in 2, 5, or 10 years. The initial system is sometimes termed the 'convenience system,' 'minor system,' or the 'storm sewer system.' The initial system may include many features ranging from curbs and gutters to storm sewer pipes and open drainageways." "Major Drainage System: That storm drainage system which carries the runof f from a storm having a frequency of occurrence of once i n 100 years. The major system will function whether or not improvements are situated wisely

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in respect to it. The major storm system usually includes many features such as streets, gulches, and major drainage channels. Storm sewer systems may reduce the flow in many parts of the major drainage system by storing and transporting water underground. The good planning and designing of a major system should eliminate major damage and loss of life from storms having a one percent chance of occurring in any given year."(?) Figure 12 illustrates the three management practices in current use. I IN FIG. 12 COMBINED MANAGEMENT STRATEGIES 29

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30 • Management Practices: These practices are often referred to as nonstructural mitigation practices of stormwater effects. These practices include: land use p lanning and regulation, flood insurance, flood proofing of structures, ordinances covering the mitigation of stormwater runoff effects, street maintenance, open space, and site design methods. The disadvantage of some of these practices is that they are often difficult to implement, regulate, and enforce.CZ) • Structural Practices: This method will be sub-divided into two categories.for this study. They will be defined as "hard" structure design and "soft" structure design. As the title indicates, structural practices include the use of structures for managing runoff. Hard structures include the use of engineered structures such as concrete drop structures, conduits, and etc. Such structures are designed with the primary objective of managing stormwater only, with little regard for the visual surroundings and contextual relationships between the structure and adjacent land use. Soft designs are those that maximize the natural drainages and conditions on the site for the management of runoff. Soft structures are designed to be compatible with surrounding land uses. Generally, hard design practices are less land consumptive than soft design responses. • Comb1nation cf structural and management practices: This third category is a comprehensive practice of management techniques which combine both non-structural

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and structural practices to manage runoff. This combined practice generally results in the most satisfactory management response. The primary disadvantage of this practice is that it requires an interdisciplinary design approach to generate a comprehensive master plan for stormwater management. Once the plan is formalized and approved, appropriate measures must be established to insure that the plan is with and the objectives of the plan are enforceable. Many communities lack the institutional resources for this practice. There are numerous structural devices and methods which can be used for the management of runoff. Such structures can be used singularly or in conjunction with other management structures and techniques. The various structural devices are categorized according to the elements of the hydrologic cycle that are being controlled. • Infiltration methods/devices: Methods which manage runoff through enhancing the natural process of infiltration/percolation attempt to reduce the total volume of runoff and consequently decrease the peak discharge rate of the runoff leaving a site. This method has the effect of reducing the amount of precipitation that becomes runoff. Infiltration devices are generally not capable of managing relatively large volumes of runoff because of soil absorption rates which are usually less than the rate of precipitation accumulation. Infiltration devices can be used for management of relatively small volumes of runoff (roof drains, small parking lots, and etc.) or they can be used in conjunction with 31

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32 other devices which do not rely on infiltration for runoff management. Specific structures/techniques for infiltration management are: • Infiltration Basins • Infiltration Beds • Infiltration Wells • Porous Pavement Such structures require soil analysis which will determine the absorption rate of the soils surrounding the devices. (ZO) The absorption rate will determine the efficiency of the management structure. • Detention/Retention Facilities: These structures enhance the surface storage element of the hydrologic system. These structures are intended to reduce the peak discharge of the runoff leaving the site. A distinction is made between detention facilities and retention facilities in that retention facilities typically hold stormwater for longer periods of time and release it at a much slower rate. Retention structures are generally larger than detention structures because retention structures usually manage larger volumes of water. Infiltration may take place in these structures but infiltration is not a design consideration in most applications. There are numerous forms of these devices, but they can usually be broadly categorized as follows:

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• Detention/Retention Basins • Detention/Retention Tanks • Permanent Ponds • Multiple Use Impoundment Areas: Parking Lot Detention Areas Roof-top Retention • Road Embankment Structures • Conveyance Structures Underground piping systems Open channels Figures 13, 14, 15, and 16 are matrices which provide a summary of considerations when selecting the management device or structure that will provide the desired runoff response. 33

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W N ...... n :;:o "T1 :J:I> :X: "'"' n :Z:.G"'l:Z.Cl z :::on c G") >--m o z l/') Vl G"'l :z -j G"'l l/')-:z • "'0 "' :z 0 :z < FTl f'T'1-0 ;::: X: .., G"'l :::0 z ,-• z o en :1> )> :z 0 l/') 0 I "' Vl "' 0 • n"' 0 c:: >< "'Tl ::z ;:o ("') • "' r--t:E-iC:: I EROSION PROTECTION 0 -< Vl -ooo.......__ l/') :::0 V') < .. > tT1 0 .., r-'"0 G"'l tT1 --< )> "' -< "' Vl -< n "' . 0 "'0 :z :z m c:. (.1') G"'l --1 :::0 -t n.,"' r-0 c:: c 0 Vl n -j "' -j ... Vl Vl 0 . 0 s I :z "' 0 -j ... ;> .., 0 -n I 0 Vl :z "' -j "' "' < 0 2 r-C> Vl -j )> "' c:: I n n 0 -j I :z c:: -j "' "' "' 0 Vl ! r-g .., c:: :z n -j 0 :z

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Another aspect of stormwater runoff management is the location of the devices used for runoff management. The location in the drainage basin where management structures are placed relative to the natural drainage patterns has a significant influence on the effectiveness of the management structures. There are three broad categories of location alternatives. The three locations (listed below) also reflect the relative scale of runoff which must be managed in each drainage basin. The three location alternatives are: • On-Site Control • Off-Site Control • In-Stream Control 35

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36 Figure 17 illustrates the three management structure location alternatives. -61ft .... IN VAI..L-E.Y "T'll-''t.. l. 611'1! 1.. !SI'f' ' 6GALE DFF FilL 17 .__ITWUCTUIII LOCAl10N8 On-Site Control: Structures located on the development site are generally intended to manage the runoff which is a result of site development. Such structures (infiltration, detention, retention, etc. are located on the developed site and resolve runoff issues prior to the water leaving the site.

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Off-Site Control: Structures located off the development site are generally used to manage runoff from a collection of developed sites. Such structures are generally larger in size thus making them more land consumptive than on-site structures. In-Stream Control: Structures that manage runoff in-stream are usually large in scope and scale (dams, reservois, etc.). Such structures are generally used for managing runoff from less frequent storm events such as the 25-100 year storm. Structures of this size and scope are generally used for flood control and management of runoff on a regional scale. Managing the adverse effects of runoff from developed sites usually has two aspects which have to be The first aspect has been discussed in the previous sections on runoff management structures which addresses the preliminary collection and mitigation of volume and volume related to time problems. The second aspect of management is the conveyance of stormwater which has been collected and managed on site from the site or management facility to a major waterway or drainageway. Conveyance structures can be categorized according to two basic types. The first type is the conduit or underground conveyance device. These structures are generally in the form of pipes and similar structures which are generally thought of as stormsewers. This method of conveyance can be more costly than open channel conveyance structures, but if land values are relatively high and underground systems result in additional revenue generating development, then such systems may be more economical than alternative conveyance structures. The second type of conveyance structure is the open channel type. Such structures vary in size and appearance and can be designed to be a development site amenity. The majority of conveyance structures in the Valley Region are the open channel type. 37

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38 ADVANTAGES OF THE WATERSHED APPROACH Stormwater management is a complex system of interrelated elements that are more effectively coordinated and implemented on a regional/watershed scale. Weston and Associates states: "In terms of stormwater management, the watershed approach entails a more comprehensive consideration of related issues. Included in this consideration is the effectiveness of different techniques such as land use planning, site design, and regional in-stream structures. The objective of the watershed approach is to achieve the best combination of alternative stormwater management measures. Overall, larger reservoir types of structures, in most cases, are more cost effective from a cost/benefit standpoint than on-site and off-site measures. This is due to the economics of scale involved as well as to the value of multipleuse benefits. Another advantage of the larger more regional control structure is more practical maintenance. Several smaller on-site structures often become unmanageable in terms of quality control and inspection during construction, and subsequent operation and maintenance. Funding and enforcement of pertinent regulations also become less complicated issues with larger regional structures. However, the planning and approval stages for regional control structures can be very complex and drawn out. More thought must be given to the proposals

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such as drainage taxes and fees in order to make the implementation of regional stormwater management structures more prevalent. In the immediate time frame, however, on-site runoff control seems to be the most practical and easiest to implement. On-site control, although not the ultimate solution to runoff problems, is an effective method of control and can play an important role, even in a regional context. (Z) • • • 39

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40 THE SOCIAL SYSTEM nE EXTENT TO WHICH RUNOFF IS MANAGED The term social system,for the purposes of this document, is taken to mean the systems and institutions created to deal with runoff and runoff management. There are two areas of concern in the social system. The first is the cultural/social environments determined by the residents of a community. Residents determine the type and kind of community in which they live as well as the services they wish their community to provide. It is the desires and aspirations of the residents of a community which prompts them to create and sustain city staffs of administrators, planners, parks directors, maintenance crews, and etc ... the institutional support which works to bring the desires of the community to fruition. The second area of concern is the institutional systems which are in place to support and sustain community services, goals and objectives. It has already been determined at the regional scale that stormwater runoff is to be managed. The extent to which it is managed is largely determined by the residents of the local community. The local community can elect to fulfill its minimal obligations in this matter, or the community may select to pursue a course which will yield them a management system which can be a community asset that responds to community needs over and above mere drainage. The degree or extent that stormwater management systems are utilized and the extent of their efficiency is largely a function of the community institutional support facilities required for development review, approval, inspection, enforcement, and maintenance of public land and structures of all types as well as runoff management structures.

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Community scale stormwater management is a large scale problem. Many agencies have been created to assist communities with developing stormwater management plans. These agencies have been created at all levels of government from relatively local agencies to the federal level. The assistance that these various agencies can provide varies from technical, and legal aid, to financial assistance. These agencies can be broadly categorized on the basis of the organizing entitles such as; federal, state, county, district, and private and cooperative agencies. The primary concern of all agencies is generally to promote stormwater management plans which not only serve the need of specific communities, but the region as a whole. The objective of these various agencies is to implement a logical and efficient management system that is appropriate to the conditions existing at the regional scale. The selection of what agencies are selected for assistance will be based largely en the development site, and the type of management devices and principles selected for management. In the Valley Region there are several agencies at all levels of government which can supply information and other assistance. From a general perspective these agencies have varying degrees of influence and little direct enforcement powers. Most of the agencies in the Valley Region are informational and organizational in nature. The enforcement aspects are generally delegated to h 1 1 . . . h. h . (211 t e oca ccmmun1t1es w1t 1n t e reg1on. ' From the legal perspective, a logic that can be followed under many, but not all situations is that the federal laws generally mandate broad guidelines and procedures, as well as certain minimum criteria of compliance. The individual states are permitted to formulate legislation toward compliance standards within the federal context. The state then forms its legislation 41

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42 along the same format to allow the local governments to establish their own criteria within state and federal guidelines and mandates. Thi s philosophy is intended to allow for legislative latitude to accommodate local conditions. The general logic then, is if the management designs are in compliance with the criteria generated at the local level, or the closest level of government, then it is very likely that the designs will meet the requirements of governmental entities progressively removed from the local level. If designs comply with a city's ordinances, the designs will likely comply with all other agencies; county, state, etc. The local level of government in the Valley Region is usually charged with the formulation, maintenance, and enforcement of ordinances, codes. A cautionary note at this point is to investigate the particular system and area that is to be managed to be sure that this logic is valid for the specific design problem. Most of the agencies that can provide assistance in designing and implementing runoff management systems can be broadly categorized as follows: • Flood Control/Floodplain Management • Erosion and Sediment Control • Water Treatment and Resue • Water Supply Development Two important agencies which must be considered when designing management systems in the Valley Region are: The Urban Flcod and Drainage Control District and The Denver Regional Council of Governments. Ancillary agencies should also be consulted for

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additional information and possible sources of funding. Some of these agencies are: Colorado Department of Highways (possible funding for bikeways and etc.), Department of Natural Resources -Game and Fish, Parks and Recreation -these and other agencies can supply information regarding multiple uses for stormwater and the lands requried for stormwater runoff management. From a water law standpoint, the Constitution of the State of Colorado regards Water rights as personal property. One significant point that emerges out of this attitude is the effect proprietary rights have on impoundment. Stormwater runoff management and the facilities and actions necessary for managing stormwater are subordinate to the water rights of upstream and downstream users and subscribers. The concept of proprietary rights translates into the situation whereby additional runoff resulting from urbanizing activities must be managed, but the extent of management must not interfere with the historic flows which existed on the site prior to its development. The current management philosophy (which in many instances is the law) is: the water falling on a given site shall be, in an ideal design situation, absorbed or retained onsite to the extent that after development the quantity and rate of water leaving the site would not be significantly different than if the site had remained undeveloped. ( 4 ) Although the philosophy just stated implies that the rate and quantity of runoff as a result of development be contained on the development site, it is unlikely that one would be faulted for adding more water to the system providing that additional water did not disrupt the hydraulic designs of the overall system. (22) Implicit in this statement is the idea that the amount of water added to a watercourse is not as critical an issue as when that additional water

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arrives at the major watercourse and is conveyed through it. This is an especially important concept in the Valley Region since this region experiences long and seasonal periods of soil moisture deficit during which times the watercourses are not flowing at full capacity. It is during such moisture deficient periods that stored runoff could be added to the watercourses. Adding water to the watercourses then, would be a function of time and watercourse capacity. There are several federal level programs which have been formulated as a result of various federal legislation. Some of the more significant legislation that affects stormwater runoff management and establishes criteria for management are: •The Federal Watershed Protection and Flood Prevention Act: (PL 83-566) of 1954. This legislation authorizes the Soil Conservation Service to aid state and local agencies in planning watershed projects, and provide funding for project implementation. The objective of the projects is flood control and upstream watershed conservation. The methods by which the objectives are attained are both structural and non-structural. •The Federal Water Quality Act of 1965: This act influences stormwater runoff management in that it mandates certain guidelines and procedures for the quality of stormwater. This legislation brings into focus the issue of nonpoint source pollution migitation. •The Water Resources Planning Act of 1965: This act directs the Army Corps of engineers to consider nonstructural techniques of controlling runoff in addition to traditional structural mitigation techniques used for flood control.

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• The National Flood Insurance Act of 1968: The National Flood Insurance Program which is administered by the Federal Insurance Administration of the Federal Emergency Management Agency. The requirement that 100 year floodplains be defined and regulations created and enforced regarding development in the areas of flood hazard has established a strong precedent in all phases of stormwater manage.ment. In addition, such action has established a strong relationship between land use control and stormwater management in general. (Z) • The National Environmental Policy Act of 1970: This act contains very general references to stormwater management, water quality, and environmental standards. The impact of the act is in the area of establishing planning frameworks, and public participation requirements for federal projects. SUMMARY: •The social aspects of stormwater management can be categorized into two elements. The goals and objectives of the residents of the community The institutional support for achieving and sustaining the community's goals and objectives • There are numerous agencies created to assist local communities with stormwater management. Such agencies exist at all levels of government. • The communities are generally the controlling and enforcing agency regarding stormwater management at 45

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the local level. Communities are required to meet criteria for management which has been created at the larger -regional scale. • Stormwater management does not take precedence to the water rights of individual subscribers. • The residents of a community determine the effectiveness of stormwater management principles and the extent to which they want their management s ystem to satisfy community needs in addition to managing stormwater. • • •

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1M PLICA TIONS OF TRENDS & PRACTICES The following examination of trends and practices and their implications is an organizational device which relates current trends in runoff management in the Valley Region to the possible implications and consequences of those trends. Trend analysis forces an of possible future consequences of current decisions. The objective is to use the device as a control element to assure that the solution to the present problem doesn't create additional problems in the future. A concurrent benefit of trend and implication analysis is that it provides an indication of the changing management methods and the strength or momentum of the infrastructural elements created to perpetuate those methods. Determining the momentum or strength behind management methods assists the planner/designer in defining the social system tolerance levels which determines the acceptability of alternative or multiple use plans and designs. There has been no attempt to evaluate whether the current trends and practices and their related implications are positive or negative, good or bad. Evaluation of practices and implications is a function of the design objectives and the specific objectives of the management principles should be generated on a case to case, site to site basis. 47

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CURRENT TREND/PRACTICE The on-site detention/retention of runoff resulting from development/urbanization. IMPLICATIONS Generally reduces costs of conveyance that would otherwise have to be implemented for rapid disposal of runoff . Many community ordinances are ill-defined which results in detention/retention facility locations haphazard and uncoordinated. Facitlity site selection is based on criteria other than management master planning.(23) Lack of master planning and site conditions when determining facility location can increase total development construction costs by removing potentially salable land from development.{23) Can increase citizen tax burden(23) • communal maintenance costs for maintaining structures which may not be necessary • land required for runoff management is removed from community tax roles Potentially increased tort liability(23)

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CURRENT TREND/PRACTICE The on-site detention/retention of runoff resulting from development/urbanization continued IMPLICATIONS Possible adverse effects on neighborhood property values(23) Facilities can be unsightly & disfunctional if not properly maintained Reduced sediment loads on downstream systems can adversely affect drainageway longitudinal hydraulic profiles which can alter system efficiencies. Communities risk implementing an overall inefficient system by utilizing detention/retention structures out of context with site conditions. (23) Possible health hazard if facilities/structures are not properly maintained. Structures can become breeding areas for insects & catch basins for toxic sediments. Retention/detention structures can improve water quality through settling & precipitation of sediments providing runoff is detained for an adequate length of time (24-48 hours). (24)

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CURRENT TREND/PRACTICE The on-site retention/detention of runoff resulting from development/urbanization continued Many communities are still using runoff structures which were implemented under the historic management principle of expedient removal of runoff. IMPLICATIONS Many communities disregard the relationship between retention/detention facility requirements and the size of development. Developments which are relatively small may not contribute a significant amount of water to the system and thus not have a significant impact on stormwater systems ... such developments may not require detention/retention facilites.(23) Potential future conflicts with water resource development . Reduced aquifer recharge along natural water courses Small impoundments haphazardly located add to the costs of consolidation if it becomes desirable to utilize impounded runoff water for potable supplies, or to implement a regional or large scale basin wide runoff collection and water utilization system. Interfacing of "new" & "old" systems must be incorporated into the process of determining a contemporary stormwater management system.

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CURRENT TREND/PRACTICE The current principle of using retention/detention facilities as a major element in runoff management is primarily applicable to new developments.( 3 ) A trend toward the utilization of natural drainage systems has been expressed by the residents of urban communities. (25) IMPLICATIONS The cost/benefit in many instances precludes retrofitting of developments constructed prior to retention/detention management criteria. A clear understanding of the term 11natural11 between the designer & the public is necessary in order to provide an acceptable design response ... true natural drainage systems can be land consumptive & tend to dictate land use rather than respond to development impacts. There is a distinction between natural drainage systems and natural appearing drainage systems. That distinction must be clearly defined between designer/planner & client. A determination of definition is required ... is this trend an expression of public attitude which states that they find 11hard11 management structures such as concrete armored channels, concrete drop structures, and corregated steel culverts less attractive and appea 1 i ng than 11soft11 management

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CURRENT TREND/PRACTICE A trend toward the utilization of natural drainage systems has been expressed by the residents of urban communities continued Runoff water quality issues are now beginning to be examined & mitigating procedures being formulated.(lB) IMPLICATIONS devices and structures such as blue/green ways, landscaped open spaces, and pocket parks that accompolish the same runoff management objectives? Natural/natural appearing management systems can be a visual site attributte. Such systems provide a wider range of design options . Such systems permit multiple uses for the land required for the management of runoff Such systems can be maintenance intensive Systems can be more land consumptive than 11hard11 systems Mitigation of poor runoff water quality can improve groundwater quality. (lO)

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CURRENT TREND/PRACTICE Runoff water qua 1 ity continued There is an increasing trend of filing for the water rights on runoff resulting from development. ( 3 ) Communities are implementing non-structural management measures (best management practices) to mitigate the adverse effects of runoff. IMPLICATIONS Improvement of runoff water quality can ease the burden on downstream water treatment fac"ilities. Conflicts can arise between the best methods for improving water quality & managing runoff quantity since problem resolution techniques between the two are not necessarily compahb 1 e Legal & communities have as yet provided a clear policy in this area. This trend will require additional legal clarification. This trend will initiate principles which will likely require the runoff to be used as a resource rather than a liability. Generally, water which has been filed on must be used or the rights to it are lost. Street sweeping equipment & similar devices are being used to mitigate both pollution and sediment problems in communities. This requires a relatively intense maintenance program since it has been observed that street sweeping equipment is effective in mitigating pollution & sediment loading only

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CURRENT TREND/PRACTICE Non-sturctural management continued Communities in the valley region are initiating drainage master plans and integrating them into the community planning and design process. Multiple use facilities with a runoff management function are now being examined and planned in valley region communities. IMPLICATIONS when repetitive passes are made with the equipment. The effectiveness of street sweeping is based on the maintenance program since the efficiency of the sweeping equipment is relatively low. (g) Non-structural practices are prompting alternative site planning measures and movement system layouts designed to mitigate runoff problems. The results of integrated planning techniques is an urban environment that is generally more efficient & attractive. Integrated planning processes which address drainage issues generally prompt planning decisions which have significant effects on land/property values. Such facilities generally require the formation of a multi-discipline design/planning team for optimum results. Multiple use facilities can reduce costs to communities if properly programmed. Costs can be

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CURRENT TRENDS/PRACTICES Multiple use facilities continued IMPLICATIONS significantly reduced for land acquisition & facility maintenance by combining park & recreation facilities with stormwater management systems. Multiple purpose systems broaden possible funding resources. Increased use of open space Increased outdoor recreation area Can improve the visual & aesthetic environments of neighborhoods & communities. Requires interfacing of runoff management systems with other community systems. Comnunities in the valley region have adopted criteria The Urban Drainage Criteria Manual(?) has been for evaluating both the initial and major storm adopted by every community in the valley region. drainage systems. This document provides a basis of organization of methods, processes, & goal definition. The document provides the framework for management which works toward a coordinated regional management plan.

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CURRENT TREND/PRACTICE Addoption of ordinances in many communities regarding runoff management and erosion control take two forms:(l 2 ) Direct address wherein the ordinances are clearly defined under drainage headings. Indirect address wherein the ordinances are not stated under classifications which deal specifically with runoff, but compliance with the ordinance will affect runoff. Although many of the legislative systems are comparatively streamlined, the legal community generally still resolves conflicts in this area on a case to case basis founded in applicable law. (23) IMPLICATIONS Such a practice requires that the designer/ planner of developments as well as the permitting agency must have a thorough knowl edge of city ordinances & policies. Ordinances may not be compatible with each other. In many instances, the legal requirements dre incompatible with the natural & social conditions existing in an area of development. A situation develops where laws are written for large scale applications & are expected to fulfill the requirements of development which usually takes place at a much smaller scale. This creates a situation of ambiguity which at the present time must be resolved in the preliminary design phase or through some method of mediation after the preliminary design phase when it has been discovered that a social or natural system's tolerance level has been exceeded.

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CURRENT TREND/PRACTICE A general overall awareness regarding the aesthetic impacts of runoff management structures is apparent. Studies are being conducted as to the social appropriateness of management structures when related to the sociocultural profiles and proximity of residential development.(23) IMPLICATIONS What structures are appropriate for the social context in which they are placed ... will some structure types be less subject to vandalism, create an environment for anti-social behavior? These questions are in the process of being answered.(23) Questions regarding the socio-economic tolerance level of the users will have to be resolved on a individual community/site basis. It must be determined if the residents will contribute indirect or direct financial support for aesthetics, and what the extent of that support will be. The socio-economic profile of the user group can _ determine the type of management practices and devices used for runoff management. Cost/benefit of management devices ... does the type of management enhance the marketability of a development? If it does ... to what extent is the marketability enhanced?

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CURRENT TREND/PRACTICE Multiple purpose facilities recieve a higher level of priority from institutional systems when requesting runoff management/drainage assistance. ( 4 ) Recent gover-nmental fiscal policies have reduced the the amount of funding available to communities IMPLICATIONS This should encourage communities to investigate the multiple purposes stormwater management devices can provide. Will encourage the development of multiple use plans and the implementation of multipie use devices. Communities will have to become more efficient in managing their urban environments if the quality of life is to remain the same or improve. There is less funding for: Design Review Inspection Enforcement Planning Maintenance Ordinance Review Ordinance Upgrading Ordinance preparation & Enactment Etc . Less action in the above categories can lead to a reduction in the quality of life for community residents.

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CONCLUSIONS SITE FACTORS DETERMINE DESIGN RESPONSE Generalized comments about complex topics, such as urban stormwater management, are subject to controversy because no general statement is correct at all times and under all circumstances. Reviewers who are trained and educated in the scientific methodology are expected to find the following conclusions especially frustrating because the comments are overviews; and as such do not focus on narrowly defined facets of runoff management which have been investigated within clearly defined boundaries, at a prescribed point in time, and under a specific set of conditions. This document is an overview investigation of urban stormwater management in the Valley Region of Colorado, and as such it is obligated to take a holistic and generalized view of the situation, and derive holistic and generalized conclusions based on the research conducted. Runoff management in the Valley Region is organized under a general strategy which allows a wide latitude of management options at the community level. These options are intended to be exercised at the local community level within the context of the regional strategy. A policy of multiple purposes for stormwater runoff and the lands used for its management is strongly encouraged in the Urban Drainage Criteria Manual.(?) The result of this multiple purpose policy is a wide range of management options which can be implemented at the community level. Un fortunately, many communities do not take full advantage of this wide range of management option and the consequences of this unexploited advantage are environments which do not fulfill their community benefit potential. This typically results in management structures and systems that are singular in purpose; which do not 59

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serve the neighborhood, community, or region to maximum advantage. Research for this document demonstrated that in many instances management structures which are perfunctorily installed for the single purpose of controlling runoff quanity without responding to local conditions and parameters are not cost efficient to the developer or the community, detract from the neighborhood and community image, and can, in fact, be detrimental to the overall regional scale runoff management strategy. (Z3 ) In order to develop runoff management strategies which respond to a variety of community needs, the tolerance levels of both the natural and social environments must be determir-ed at both the regional and community Once these levels have been determined the extent to which the management objectives exceeds the natural and social environments' tolerance levels can be reasonably evaluated. At this point, the impacts of management decisions can be evaluated and options and alternatives can be more efficiently assessed. A key issue in runoff management is the formulation of goals and objectives. Although the Urban Drainage Criteria Manual implies a strategy of runoff quantity management as the major objective, the strategy is broad enough in scope to permit multiple use concepts for both the land utilized for runoff management and the additional runoff water generated as a result of urbanizing activities. The most effective and efficient point in the management system to initiate plans for multiple uses is at the point in the process where management objectives are determined. The general objective should be expanded from the singular one of managing quantity problems alone, to managing quantity problems while enhancing the natural and social environments of the community. A concept that could be broadly applied within the Valley Region would be to internalize and resolve

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conflicts and problems locally within the boundaries of the community or area which are generating them. The implementation and success of such a concept is predicated upon an adequate supply of inventory and baseline data as well as an agreement among the populace that passing problems on to their neighbors, either upstream or downstream, is an undesirable condition. Among the Denver Regional Council of Governments, among its other functions, serves as both a repository of data and information, and a forum where local governments can meet and resolve conflicts and problems which affect each other. Urban stormwater management is a complex structure of interrelated elements and as such is not without its problems. Perhaps the msot significant problem is the gap between the management principle and objectives, and the actual results of those principles when they are transformed into realtiy. There is little basis for argument against the idea that stormwater management should be initiated at the regional scale with the appropriate objectives as guiding principles. But, the success of any large scale plan is essentially based in the efficiency and effectiveness of the subordinate elements working in general harmony toward the success of the regional plan. In the Valley Region the regional objectives have been more or less clearly stated. The objective is to manage stormwater and mitigate its adverse effects on the regional scale for the benefit of the environment within the defined region as well as the environment outside the defined region. Generally, this benefit has been defined and determined based on engineering and hydrologic principles. These principles have formed the regional scale framework within which the various subordinate elements (the communities) must function. The administrators of the regional scale principles have provided communitieswithinformation on various management structures, and how to establish a management 61

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62 system that satisfies the objectives of the region. In spite of numerous agencies and a satisfactory regional scale objective, it appears that the gap between the individual communities needs and objectives and the regional scale principle has yet to be bridged. One solution that would bridge the gap between the local and regional levels is to understand the needs, objectives, and principles of the regional management structure and have the ability to enter the focal participating community, determine community needs, and provide a community system which satisfies and objectives of the region as well as respond to the needs of the community. It would appear that the regional level administrators have established the desirable objectives and guidelines for regional scale runoff management and, to a point, have established the methodology by which these regional objectives are to be attained. The detention/retention method appears to be the general method of management and receives a great deal of regional level institutional support. Many of the suggestions for management methods proposed for runoff management at the community level involve the retention/detention devices. The major supply of data and information support the detention/retention method. However, it is not to say that this is the optimal management method under all conditions and all situations. The selection of the management method at the community scale can and should respond to local needs over and above the the utilitarian and single purpose of drainage. The communities have been permitted this latitude under the organization of the regional system. In general, how communities resolve their runoff problems is left to them as long as the resolution satisfies the reg:onal objectives. Typically it is the community's responsibility to devise and

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implement a stormwater management system which offers the most rewards for the community while fulfilling the objectives of the region. Many communities lack the institutional resources to develop, construct, enforce and maintain a runoff management system that provides all the community rewards that the management system is capable of providing. The of multiple uses for stormwater management systems is supported at the regional level, but determining the optimum multiple uses for the runoff management systems has been left to the individual communities. The challenge for local communities is to match the needs and desires of the community to.the stormwater management system's capacity for fulfilling those defined needs and desires within the regional framework. It is the local communities that know their problems most intimately and the resolution of those problems is dependent upon local conditions. It is for this reason that a great deal of latitude in management response has been established. " ... the definition of the design situation will specify a particular set of design objectives. These objectives will state to what extent and in what manner the runoff from a given site should be controlled."(Z) There are two fundamental elements of stormwater management which are of concern to the community when it begins to formulate a runoff management strategy that satisfies the regional plan. The first element is the runoff water which is generated as a result of development. The second element that must be examined is the land required for managing the runoff water. Figure 18 is a simplified flow diagram of stormwater management. It illustrates the typical process by which the runoff water can be managed.

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EVAPORATION PERCOLATION/ INFILTRATION MANAGEMENT OF CONDUCT! ON/ STORMWATER WHICH r-DISPOSAL DIVERSION T O EXCEED S MAJOR DRAINAGEWAY PRE DEVELOPMENT AMOUNTS & RATES DETENTION DISPOSAL ON A DOWNSTREAM S lTE AT PRESCRIBED AMT. S & RATES DEVELOPER'S ..._ GENERAL STORMWATER -MANAGEMENT RETENTION RESPONSIBILITIES USUALLY REQUIREES --MEASURES TO COMPENSATE FOR EVAPORATIO N LOSSES ,...._ ACCEPTANCE & MANAGEMENT O F TREAT & USE FOR POTABLE -STORMWATER SUPPLIES .4RRIV1NG ON THE UTI ll ZATION: DEVELOPMENT SITE DIRECTLY RELATED AQUIFER RECHARGE TO WATER QUALITY RAW WATER IRRIGATION RECREATIO N AESTHETIC ....._ MANAGED WATER FROM UPSTREAM DEVELOPMENTS UNMANAGED WATER FROM DEVELOPMENTS CONSTRUCTED PRIOR TO "STORMI
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The most fundamental decision in the entire process is the decision by the community to either adopt a management concept that utilizes their runoff water for community needs, or adopt a policy that regards runoff as a liability or waste byproduct of development which must be disposed of. If the decision is to utilize the runoff water, then decisions have to be made regarding what the optimal uses might be and then formulate a physical s ystem which will support those uses. If the decision is reached that disposal of the water is the most viable alternative for the community, then the physical system will have to support the decision. A third option is to develop a system which disposes of the water for the present, but can be modified with little effort to utilize runoff water in the future. The complexity of the objective is a reflection of the complexity and detail to which the plan must be carried out and enforced. There are multiple use benefits for stormwater ... what those multiple use benefits are and how they are obtained is determined by the forces acting on the community and site conditions. The second element of stormwater management is the land required for managing runoff. There has been a tendency on the part of many communities to adopt suggestions made by the regional administrators and transform those suggestions into ordinances and resulting physical structures without examining the specific needs and conditions of the community. This practice has resulted in problem solutions that are out of context with the conditions of the site. In other words, communities are adopting measures which are not necessarily solutions to their problems. Such measures are implemented out of context to either the engineering goals of runoff management or the surrounding environment's needs. In order to alleviate this situation a clear understanding of the regional goals, community needs, and management is necessary.

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One method by which communities can begin to formulate a runoff management strategy which will fulfill its community potential is illustrated in Figure 19 . FIG. 19 PROCEDURE FOR DETERMINING THE APPROPRIATE MULTIPLE USES FOR RUNOFF MANAGEMENT SYSTEMS The first step is an inventory process which is conducted to determine the social and natural forces acting on the community. The inventory phase should focus on determining the type of stormwater management system utilized in the community at the time of inventory. The system concept should be determined and an inventory of institutional support systems should be conducted to determine if the community has the institutional support to perpetuate the runoff management concept or future alternative 66

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concepts. The next step is to determine if the in-place management system is an optimum system based on: • The in-place runoff management system's ability to fulfill the objectives of the regional scale plan. •The physiological, andinstitutional forces existing in and around the community. Once the type of system used for managing stormwater has been determined, and an evaluation of the system's effectiveness has been made based on the physiological, sociocultural, and institutional support existing in the community the next step is to determine the conflicts that exist in the system. An example of a system conflict might be that the community has established desirable goals and objectives that are beyond the capabilities of the city's institutional support system to implement or maintain. Such conflicts should be identified and resolved before proceeding to the next phase of plan development. The next phase of determining a multiple use plan for runoff management is to develop a concept of multiple use which responds to the physiological, sociocultural, and institutional systems tolerance levels as determined in the preceeding phases. Once the optimum use concept has been determined, the next step is to formulate designs for the physical environment that support the developed multi-use concept. An important step in the process is to develop guidelines for future developments that will perpetuate the previously formulated concept. Ideally the guidelines will provide the community with a continuous visual theme and which will allow future 67

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developments to be integrated into the management system without disruption of the proposed multi-use management system or the physical environment. Every community is unique. The challenge to the designer/planner is to identify what physical, social, and institutional forces are acting on the specific community and utilize that information to formulate stormwater management systems which allow the community to develop their own individual system which results in the stormwater management element of the urban organism to be developed to its full potential. • • •

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REFERENCES 1. Webster's New Collegiate Dictionary. Springfield, Mass. 1975. 2. Roy F. Weston, Inc. Environmental Consultants-Designers. Storm Water Management Design: A Manual of Proceedures and Guidelines. Kenneth C. Wiswall, Project Engineer, and K.S. Shumate, Ph.D., Project Manager. Prepared for the Maryland Department of Natural Resources. Westchester, Pennsylvania: Roy F. weston, Inc. June, 1972. 3. Interview with Gary Mast, Principal Planner Water Resources Management, and John T. Doerfer, Water Quality Planner, Denver Regional Council of Governments, Denver, Co, 4 Nov. '82. 4. Urban Land Institute, National Association of Homebuilders, and the American Society of Civil Engineers. Residential Storm Water Objectives, Principles, & Design Considerations. New York, N.Y., Washington, D.C.: Urban Land Institute, National Association of Homebuilders, and the American Society of Civil Engineers, 1975. 5. U.S. Environmental Protection Agency. A Primer on Wastewater Treatment. Pamphlet, Washington, D.C.: GPO, (A-107), 1976. 6. U.S. Environmental Protection Agency. Clean Water: Understanding The Law. Pamphlet, Washington, D.C.: GPO, ID No. 1978-260-880:69, 1978. 7. Wright-Mclaughlin Engineers. Denver Regional Council of Governments Urban Storm Drainage Criteria Manual. 2 vols. Denver, Colorado: Wright-Mclaughlin, March, 1969. 8. Sheaffer, John R., Kenneth R. Wright, William C. Taggart, & Ruth M. Wright. Urban Storm Drainage Management. New York, N.Y.: Marcel Dekker, Inc., 1982. 9. Novotny, Vladimir, Ph.D., P.E., and Gordon Chesters, Ph.D., D.Sc. Handbook of Nonooint Pollution Sources and Management. New York, N.Y.: Van Nostrand Reinhold Co. 1981. 10. Development Research Associates, Inc. & Wallace, McHarg, Roberts & Todd, Inc. Regional Transportation District Interim Report Ecology. np. nd. 11. Wright-Mclaughlin Engineers, Engineering Consultants. Technical Memorandum Factors Affecting the Cost of Erosion Control Planning. Prepared for: Denver Regional Council of Governments. Draft Document. June, 1982. 69

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70 12. Wright Water Engineers. Technical Memorandum Costs to Local Governments for Implementation of Erosion Control Programs. Prepared for: Denver Regional Council of Governments. Draft Document. July, 1982. 13. Wright-Mclaughlin Engineers Engineering Consultants. Supplemental Report. Cost of Erosion Control Measures. Prepared for the Denver Regional Council of Governments. May, 1982. 14. Mast, Gary N. Managing Erosion and Sedimentation From Construction Activities. Denver Colorado: Denver Regional Council of Governments. April, 1980. 15. Colorado Department of Highways. Erosion Control Manual. Denver, Co:Colorado Dept. of Highways, 1978. 16. Michigan Department of Natural Resources. Mich igan Soil Erosion & Sedimentation Control Guidebook. Lansing, Mi: Michigan Department of Natural Resources. 1975. 17. U.S. Dept. of Agriculture, Soil Conservation Service. A Guide for Erosion & Sediment Control in Urbanizing Areas of Colorado . Interim Guide. Denver, Co: Soil Conservation Service. nd. 18. Denver Regional Council of Governments. Summary First Year Progress Report of the Denver Regional Urban Runoff Program. In cooperation with, U.S. Geographical Survey Subdistrict, Urban Drainage & Flood Control District, and the Member Governments of the Denver Regional Council of Governments. 1979. 19. Denver Regional Council of Governments. Summary Second Year Progress Report of the Denver Regional Urban Runoff Program. In cooperation with, U.S. Geographical Survey Subdistirct, Urban Drainage & Flood Control District, and the Memeber Governments of the Denver Regional Council of Governments. August, 1981. 20. Colt, Jon L. Percolation Pits: Their Design, Construction, Use, and Maintenance for Stormwater Disposal, Groundwater Recharge, and Surface Water Quality Protection in Adams County, Colorado. A brochure prepared by the Adams County Planning Department, Brighton, Co. nd.

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21. Interview with Ben Urbonas, Chief of Master Planning Programs, Urban Flood and Drainage Control District, Denver, Colorado, Oct. '82. 22. Interview with Davis Holder. College of Design and Planning, University of Colorado at Denver, 4 Nov. '82. 23. Jones, Jonathan E., and D. Earl Jones. "Interfacing Considerations in Urban Detention Pending." Presented at the August 1-6, 1982 Engineering foundation/ASCE Conference, "Planning, Design, Operation, and Maintenance of Storniwater Detention Facilities," at Henniker, New Hampshire. 24. Whipple, William, jr. and Joseph V. Hunter. "Settlement of Urban Runoff Pollution." Journal of the Water Pollution Control Federation. Vol. 53, No. 12, Dec., 1981, pp 1726-1731. 25. Laszewski, Edwin J. "Problems of Public Acceptance: Storm Drainage Through Natural Watercourses." Published Proceedings of a research conference, "Urban Runoff Quantity & Quality." Held at Franklin Pierce College, Rindge, New Hampshire, August 11-16, 1974. Published by the American Society of Civil Engineers. • • • 71

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ISSUES TO LANDSCAPE ARCHITECTS Although each urbanizing site and situation promotes its own discrete set of runoff management problems, conflicts and issues have to be resolved at both the regional and local level, the three issues of overiding concern are: • Best land use practices for communities • Runoff water quality (nonpoint source pollution) • Runoff water quantity (volume & rate) This rank order list is not to suggest that the problems and challenges presented in one category are of less importance than those perpetrated in other categories. Issues related to runoff quantity are, at present, of very high priority and of course have to be addressed and resolved. But, runoff quantity management by virtue of the fact that it consumes physical space in the environment becomes a land use problem. By this reasoning quantity, and to a lesser extent quality, management become elements of a larger issue ... land use. The ranking then, is not an issue of subordination of priority resolution, but a ranking of elements within the organizational taxonomy. Within this taxonomy, runoff quality management is ranked higher than quantity management. This ranking was based on the comparative prcgress of study between the two fields. Issues concerning runoff quantity are in a much more advanced position of study and clarification. Issues concerning runoff quality, by comparison, are not as advanced as those concerning quantity. The significance of the engineering and scientific "distance" between these two elements can be very dramatic. The issue of water quality is barely out of the scientific stage, whereas quantity 72

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73 management is well into the engineering stage. It is unlikely that scientific advancements in quantity management will perpetrate, by comparison, a drastic change in land use and physical form. Quality issues however, present a relative unknown in the algebra of runoff management. Mitigation of water quality problems could easily result in significant changes in the land use and runoff management structures. Ranking water quality above quantity is also a reflection of the need for baseline (pivotal decision) information. An example of this situation is; issues regarding runoff quantity can usually be quantified, and as a result of this quantification engineering and design criteria can be formulated. Conversely, water quality is still in the process of being defined. Urban stormwater management is a complex and multifaceted field which contains all the elements that the landscape architect's methodologies and processes are designed to manage effectively. The field involves responding to multiple objectives, multiple and diverse stimuli from both the natural and social systems, diverse data and information which are both quantifiable and unquantifiable. The field must attempt to resolve generalized problems whose definitions are broad in scope and scale and comprised of numerous elements. The resolution of most management problems require the organization and synergization of data that have been extracted from a wide variety of focused and specific data categories regarding specialized facets of management which have been generated by the scientific and engineering methodologies. At the present time the scientific and engineering communities are feeling the pressure from the public sector to resolve broad based and multifaceted management problems. (ZS) It is at this

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point that a dichotomy between the problem and the methodology utilized for its resolution begins to manifest itself. The scientific and engineering methodology is remarkably efficient when dealing with subjects that are quantifiable, well defined, and limited in the number of imputs. The scientific and engineering methodologies become less effective from a social and cultural environmental perspective, as variables increase in numbers and latitude. The issue to landscape architects is to respond to the challenges of a diverse, often stochastic, and multifaceted problem utilizing the methodologies and processes unique to the profession to: • Produce physical forms which are compatible with the natural and social environments. • Produce the plans which will facilitate physical forms. • Assist in determining the best management practices based on the regional requirements and the needs of the individual community. The forms and practices must be responsive to the natural and social systems' tolerance levels and enhance the natural and social environments as they are defined by the residents of the community. It is the multiple purpose concept that will produce management systems which are appropriate to context and avoid systems which are single purposed, functionally utilitarian, and environmentally discordant. • • • 74

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HYPOTHESIS: The formal hypothesis stated below will serve as a guide for the further investigation and response to the problems concerning urban stormwater management. The statement will be applied to the systems in and around the City of Lafayette, Colorado. If runoff management systems in the Valley Region are designed for multiple uses based on social and natural system's tolerance levels; then social and natural environmental quality will be enhanced. • • • 75

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CASE STUDY, BUDGET, & TIME LINE The case study for this project will be the City of Lafayette, Colorado. The primary area of the case study will be determined after an examination of the drainage conditions existing within Lafayette and the surrounding area has been completed. The case study at this point may be of necessity restricted to a single drainage basin located in the described area. The project budget has not yet been determined The timeline for the project is: •Dec. 27-31: review drainage master plans for Lafayette and surrounding area • Jan. 3-7:conduct area reconnaissance • Jan. 10-14: declare case study area and begin sociological and natural systems inventory • Jan. 17-21: develop trends and implications analysis • Jan. 24-28: formalize background data • Feb. 1-4: Declare and define problem statement • Feb. 7-11: refine and formalize data and statements • Feb. 14-18: conduct feedback loop evaluations • Feb. 21-March 11: begin rough draft document • March 14-25: feedback response to rough draft of work completed to date •March 28-31: prepare rough draft of final document •April 1-15: formalize final document The timeline presented above is subject to revision and adjustment. • • • 76

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THESIS COMMITTEE Daniel B. Young, Program Director, Landscape Architecture, College of Design and Planning, University of Colorado at Denver Jerry Shapins, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver Tom Haldeman, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver Lori McMillan, Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver Jeffrey Pecka, ASLA, Landscape Architect and Environmental Planner, 99 Corona, Denver, Colorado 80218 Thomas A. Colbert, CPSS, CPAG, President T.A.C.A. Corporation • • • 77

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OPTIMIZING URBAN STORMWATER MANAGEMENT FACILITIES THROUGH MULTIPLE USE A TEST CASE: CITY OF LAFAYETTE, COLORADO JOHN V. GOEBEL 1875 BEDIVERE CIRCLE • LAFAYETTE • COLORADO 80028 • (303)688-8458 This case study was prepared and submitted as partial fulfillment of the requirements for a Master of Landscape Architecture Degree from the College of Design and Planning, University of Colorado at Denver. Daniel B. Young, Program Director Date

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THESIS COMMITTEE Daniel B. Young Program Director, Landscape Architecture, College of Design and Planning, University of Colorado at Denver. Jerry Professor o Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver. Torn Haldeman Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver. Lori McMillan Professor of Landscape Architecture, Landscape Architecture Program, College of Design and Planning, University of Colorado at Denver. Jeffrey Pecka Landscape Architect and Environmental Planner, 99 Corona, Denver, Colorado 80218 Thomas A. Colbert, CPSS,CPAG President T.A.C.A. Corporation JURISDICTIONAL CONTACTS Micheal Acirnovic Lafayette City Administrator, 201 East Simpson Street, Lafayette, Colorado 80026 KathX Davis Plann1ng Director, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026 Tom Hoby Director, Parks, Recreation, and Open Space, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026 Warren Williams Director of Public Works, City of Lafayette, 201 East Simpson Street, Lafayette, Colorado 80026

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TABLE OF CONTENTS SECTION I Methodology SECTION II Existing Conditions SECTION III Suggested Multiple Uses SECTION IV General Policies and Guidelines Appendix 1 Data Base Appendix 2 Reference Maps Appendix 3 Lafayette Objectives Page 3 Page 8 Page 53 Page 76 Page 101 Page 103 Page 118

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EXECUTIVE SUMMARY This booklet is part II of a two part project which applies the data and information generated in Part I (the research document) to the specific geographical area of Lafayette, Colorado. This is a community scale design case study which proposes multiple uses for underdeveloped stormwater management facilities in the rapidly urbanizing City of Lafayette, Colorado. Lafayette is a city with a population of approximately 10,000 located fifteen miles North of the Denver City limits and eight miles East of the City of Boulder, Colorado (see Vicinity Map, fig. 1). Lafayette is one of the rapidly urbanizing areas comprising the front range urban corridor whose land use is in a transitional state from primarily rural/agricultural to urban/suburban use. The overall purpose of this study is to provide ideas and alternative uses for lands required for stormwater management which will enhance the quality of life for the community's residents and improve community image. The document is intended to be used by those who are interested in the urban planning and design processes of the City of Lafayette, and by those persons who are interested in gaining additional community benefits from lands already in the public domain. This case study recommends multiple use alternatives for underdeveloped stormwater management facilities. These multiple use alternatives are proposed as a means to elevate the awareness of stormwater management facilities as an underdeveloped community resource which can be further integrated into the urban design process. The final decision on what recommendations and alternatives are to be implemented and the priorities of implementation are left to the people who know the community; the residents of Lafayette. This case study is divided into several sections as described below. • Section I is an explanation of the methodology used throughout this project phase which provided the basis for study direction and decision making.

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2 • Section II contains a brief description of the existing stormwater management conditions found in Lafayette. Thi s secti on also includes a discussi on of the selected multi-use concept, the selection of which was based upon the unique natural, sociocultural, and institutional conditions existing in and around the City of Lafayette. • Section III describes a range of suggested multiple uses for stormwater management facilities which can be implemented based on identified community needs and the conditions which exist at specific stormwater management facility sites. • Section IV suggests guidelines for developing multi-purpose stormwater management facilities. These guidelines are intended for use in areas that are in transition from rural land use to urban land use. However, many of the guidelines can be applied to areas already urbanized but contain underdeveloped stormwater management lands. This case study is prepared with the point of view that stormwater drainage is a necessary element of the urban development process and that the lands required for drainage facilities can be developed and utilized to provide additional community benefits without radical alterations to either the management facilities them selves, or the institutional support systems which are responsible for the implementation, operation, and maintenance of public spaces and facilities. A portion of the expenses for materials and reproduction of this case study have been funded by the City of Lafayette, Colorado. • • •

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TRAIL JUNCTION/ ACTIVITY NODE -z 0 5 w tJ)

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INVENTORY ANALYSIS RESPONSE DETERMINE THE TYPE OF STORMWATER MANAGEMENT SYSTEM UTILIZED IN THE PROJECT AREA • DETERMINE SYSTEM CONCEPT • EXAMINE INSTITUTIONAL ORGANIZATION & EXTENT OF SUPPORT DETERMINE THE APPROPRIATENESS OF THE IN-PLACE MANAGEMENT SYSTEM BASED ON THE FOLLOWING CONDITIONS: • PHYSIOLOGICAL • SOCIOCULTURAL • INSTITUTIONAL IDENTIFY & RESOLVE ANY SYSTEM POLICY CONFLICTS DETERMINE THE OPTIMUM MULTI-USE CONCEPTS BASED ON THE TOLERANCE LEVELS OF THE FOLLOWING CONDITIONS: • PHYSIOLOGICAL • SOCIOCULTURAL • INSTITUTIONAL GENERATE FORM RESPONSES FOR THE BUILT ENVIRONMENT GENERATE GUIDELINES FOR FUTURE DEVELOPMENTS WHICH WILL: • PERPETUATE THE CONCEPT/CONCEPTS GENERATED ABOVE • PROVIDE A CITY-WIDE CONTINUITY OF DESIGN THEME • FACILITATE THE INTEGRATION OF FUTURE DEVELOPMENT DRAINAGE SYSTEMS FIG. 2 PROJECT PROCEDURE 3

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OBJECTIVE The objective of this case study is to develop a multiple use program for the lands required to manage stormwater runoff which will enhance both the community image of Lafayette and the quality of life for its residents. The determinants on which the multi-use program is to be based are as follows: GOAL • NATURAL ENVIRONMENT: The opportun1t1es and constraints of the physical environment in and around the City of Lafayette. • SOCIOCULTURAL ENVIRONMENT: The defined goals and objectives of the residents of Lafayette. • INSTITUTIONAL ENviRONMENT: The capabilities of the existing institutional support systems such as the city staff, as well as the capabilities of the various agencies and systems which have been created to assist local governments with community development. • • • The project goal is to produce a program of multiple uses for stormwater management facilities that are compatible with the plans, agencies, and systems which exist in and around the City of Lafayette, and to produce a program which can respond to future growth impacts in a smooth and efficient manner. • • • 4

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5 METHODOLOGY The methodology used in the preparation o f this study involved the following phases. • INVENTORY: An inventory of existing conditions in and around the City of Lafayette. • ANALYSIS: An analysis and interpretation of the data and information collected in the inventory phase. • RESPONSE: The formulation of design suggestions and guidelines that are compatible with the local conditions as they are defined in the previous two phases. The specific procedure that was followed during the preparation of this case study is outlined in figure #2. As can be determined from the outline, a specific focus of the inventory and data gathering phase was the determination of the type of stormwater management system that is currently being used in the City of Lafayette, and the extent of the institutional support behind that management concept. These points; management concept and the extent of institutional support, were examined and analyzed in addition to the natural and social forces acting on the City of Lafayette as they are defined in the documents listed in appendix #1. As a part of the analysis phase, an evaluation of the appropriateness of the in-place stormwater management system was made based on the natural and social environments in and around Lafayette as well as the capabilities of the institutional system supporting the existing management policies. This evaluationwas made after the data gathering and inventory phases were concluded. The next phase of the procedure identified and resolved, at the policy level, any system conflicts that were disclosed as a result of the data gathering and inventory phase. In the case of Lafayette the system conflicts and suggested resolutions are mainly policy issues and as such do net present physical obstacles to implementing multiple uses for stormwater management facilities.

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The response phase of the procedure, the final phase, involved the following three steps. • The formulation of an optimum multi-use concept which was tailored to the capabilities and acceptability levels of the natural, social, and institutional environments in Lafayette. • The development of plans for physical forms for the built environment which were directed by the concepts formulated in the previous step. • The formulation,of guidelines for future developments which will perpetuate the concept formulated in step 1, provide a continuity of a design theme for the city, and facilitate the integration of runoff management systems and facilities which will result from future development. In keeping with the goal of producing a multi-use program for stormwater management facilities that would be compatible with both existing and future plans for the City of Lafayette, the inventory phase included the following tasks: • A complete review of all the planning studies produced by the City of Lafayette. A complete listing of these documents can be found in appendix 1. • Information exchanges with the following parties: City Administrator City Planning Director City Parks, Recreation, and Open Space Director City Public Works Director 6

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7 Visual inspections of the following sites and facilities: • Areas of Lafayette which are currently being used to manage stormwater. • Existing park facilities in Lafayette • Land areas in Lafayette that are designated for development as future park spaces • Areas in and around Lafayette that are designated as open space • Sites located in neighboring communi ties where stormwater management lands have been developed for additional community uses A review of planning documents for areas adjacent to the City of Lafayette. • • •

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STORMWATER MANAGEMENT IN LAFAYETTE The type of stormwater management system used in Lafayette at the present time is directed by two major documents which are intended to work in conjunction with each other. These two documents are: !."City of Lafayette and Surrounding Unincorporated Areas of Boulder County, Colorado Storm Drainage Design and Technical Criteria." 2."Major basinwide Planning City of Lafayette/Boulder County Phase B Development of Preliminary Plan." Together, these two documents establish a management policy of collecting, detaining, and conveying stormwater runoff through a system of open channels and detention facilities. From an analysis point of view, the proposed drainage system which will result from implementing the policies and procedures defined in the two documents is, in general, appropriate based on Lafayette's natural, social, and institutional support systems. The physical facilities and structures that will result when the Phase B Plan is implemented, combined with the policies and resulting forms generated by the Technical Criteria, offer unique opportunities for multiple uses. Although the Technical Criteria and Phase B preliminary Plan are intended to work in conjunction with each other, they are two different documents. The Technical Criteria document is, in general, a policy document, whereas the Phase B development Plan is a city-wide physical design plan for major drainageways. At the present time the Technical Criteria is being implemented at the policy level and the status of the Phase B Development Plan is in the preliminary phases of implementation. The current planning status of the Phase B plan offers Lafayette the unique opportunity to incorporate multiuse concepts with the physical drainage designs in the preconstruction phase. The expedient implementation of the Phase B Development Plan should be regarded as a high priority project by the City of Lafayette. This evaluation is based on the B

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9 data and information contained in the Phase B Development Plan which defines an existing flooded area hazard in many areas of the city. (See figure #3) This flooded area hazard is not likely to be resolved by the enforcement of the Technical Criteria alone. According to the Urban Flood and Drainage Control District the best way to mitigate the flooded area hazard that presently exists in Lafayette is to fully implement the Phase B Development Plan. FIG. 3 POTENTIAL 100-YEAR FLOODED AREA MAP CITY OF LAFAYETTE AND SURROUNDING BOULDER COUNTY •.... .. 1 LEGEND PJaoin -.,.,. 100 YFloodplai" IWIOO<--

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In order to mitigate the flooded area hazards illustrated in figure 3, the Urban Flood and Drainage Control District has proposed a system of open channel drainageways. These drainageways are illustrated in figure 4. The primary purpose of the proposed drainageways illustrated (BASE MAP• USGS REVISED 1971) Original base map from, ''Major Basinwide Planning City of Lafayette/Boulder County Phase B Development Plan." Camp, Dresser, & McKee, 1980. FIG. 4 OPEN CHANNEL DRAINAGEWAYS 10-YEAR ANO 100-YEAR DESIGN STREAMA.OWS CITY OF LAFAYETTE AND SURROUNDING BOULDER COUNTY LEGEND [BID-a,o (cfsl

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in figure 4 is to convey stormwater runoff which has been collected, briefly stored, and released at prescribed rates from various developments within the defined drainage basin boundary. The regulated water is conveyed from the de veloped/developing areas via the seven major drainageways and discharged into Coal Creek. Figure 5 is a simplified diagram which illustrates the general relationship between the proposed drainageways, creeks and ditches, and developed areas. The relationships and elements illustrated are within the Lafayette planning area boundaries. Figure 5 illustrates how the proposed conveyance structures provide a physical connection between developed and developing areas with Coal Creek. The Technical Criteria establishes the use of detention ponds as the primary method of regulating stormwater quantities and rates of flow leaving a developed site to those levels which existed prior to development. The use of detention ponds generally create open areas which are infrequently inundated by stormwater. Since these areas are only infrequently used to detain stormwater they offer an opportunity for use as developed open spaces, parks, and recreation facilities. STATUS & CONDITION The general status and condition of the stormwater management facilities in Lafayette offer opportunities for improvement. These opportunities for improvement can be classified into two general catagories; the structures themselves (existing drainageways, detention poinds, and etc.), and policy issues (coordination and implementation of drainage facilities on a city-wide basis). From a structural perspective the two major problems are erosion and sedimentation. Bank erosion and channel erosion are deteriorating many of the open channel drainageways and detention This structural deterioration results in the following impacts: • Reduced operating efficiency of the structure and the system it was designed to serve.

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(-"'1 DEVELOPED ARE.A.S ...... ./ PLANNING AREA BOUNDARY --CITY LIMITS (1983) • • • • .. • • • •••• PROPOSED ORAl NAGEWAYS ,,-.... , I ' .. \ . // . . L) • • . -.. -CREEKS/DITCHES POSSIBLE DESTINATIONS DEVELOPED DESTINATIONS AG. 5 PROPOSED DRAINAGEWAYS, CREEKS, & DITCHES AS RELATED TO DEVELOPED AREAS & DES11NA110NS

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'13 • Sedimentation which can obstruct water flow and result in bank overtopping and flooding. • Destruction o f conveyance structures such as street culverts, detention pond control structures, and etc. If drainage structures are left to deteriorate, they progressively lose their ability to mitigate the adverse conditions for which they were originally designed. In many instances deteriorated drainage structures exacerbate the adverse conditions they were originally designed to alleviate. Bank and channel erosion appear to be a particular problem in those facilities installed prior to the adoption and enforcement of the storm drainage and design criteria. Increased maintenance and upkeep of existing facilities will alleviate their deterioration and insure that the facilities will function properly when they are needed most. The second category which offers opportunities for improvement of stormwater management facilities in Lafayette is the implementation of a coordinated system of drainageways of adequate capacity, which will convey the collected and regulated runoff from the various development sites to the major drainageway serving Lafayette (Coal Creek), At the present time Lafayette lacks such a system. More simply, (see figures 6 and 7) Lafayette has a major waterway, Coal Creek, which accepts the runoff from the majority of the city's land areas. The city also has implemented storm drainage design criteria for developing areas which collect and regulate the runoff generated as a result of development. The excess at the development sites has no programmed system of drainageways to convey the collected stormwater to the point of its natural discharge, Coal Creek. The planning and engineering design phase necessary for the implementation of conveyance structures for the city has been completed, (Phase B) and the implementation phase is currently in the planning stages. The physical implementation of the Phase B Development Plan will mitigate the flooding hazard which now exists in the city between the developed areas and the natural drainageway, Coal Creek.

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. .. 0 FIG. 6 EXISTING CITY-WIDE DRAINAGE SYSTEM CONCEPT PLAN 14

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FIG. 7 PHASE •a• DEVELOPMENT PLAN CONCEPT DIAGRAM A major obstacle to the implementing the Phase B Development Plan is the lack of funding. The available financing for drainage structure construction, maintenance, and operation is relatively limited. A concept that can expand the range of possible funding sources is to develop drainage systems which perform multiple community functions. An expanded range of funding sources could go far toward implementing the Phase B Development Plan which is the vital missing link in Lafayette's stormwater management system. Without a coordinated conveyance system of adequate capacity, such as the system proposed in the Phase B Development Plan, stormwater on a city-wide scale remains unmanaged, and this can result in a continuation and possible increase in flooding hazards.

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ADDITIONAL STUDIES An investigation of development rates, patterns of development, and constraints to development, such as subsidence hazards in and around the City of Lafayette, indicate that additional drainage studies should be conducted in the very near future. The pattern of development in Lafayette is beginning to extend beyond the boundaries of the Phase B Development Plan. Land areas are now being planned and developed which are outside the programmed drainage areas outlined in the Phase B Development Plan. In order to provide these areas with a safe and adequate system of stormwater management, basins adjacent to those already programmed in the Phase B Development Plan must be similarly programmed. Development plans for land areas adjacent to those areas defined in the Phase B Development Plan should be programmed as soon as practicable if urban growth is to proceed efficiently and economically. FORMULATING A CITY WIDE MUL Tl-uSE CONCEPT There is a wide range of multiple uses for both the land required for runoff management and the increased amounts of runoff water which are a usual consequence of development. A community has the option of adopting a range of multiple use alternatives based on specific conditions existing in particular areas of the city, or the community can adopt a single alternative use concept and apply that concept on a city-wide basis. One of the early decisions that should be made by a city considering multiple uses for their stormwater drainage facilities is the decision to; 1. adopt more than one multi-use alternative, or 2. to adopt a single, city-wide multi-use concept. This decision should be based, to a large extent, on the city's institutional system and the external, regional institutional and financial support systems which exist to serve individual communities. In general, it is difficult for most cities to support and sustain more than a single, city-wide multi-use concept. One of the major reasons for this difficulty is the limitations of the city's institutional system to absorb the additional work load required to service several, smaller scale multi-use systems. The adoption

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of several multi-use alternatives increases the complexity of the business of running a city and therefore the workload placed on the institutional support systems as well as increased expenditures needed to support the different multi-use concepts adopted. The adoption of a single, city-wide multi-use concept is less detailed and less complex which usually results in a system that is more easily managed and administered, The data and information reviewed for this study indicates that the residents of Lafayette would likely be best served by a single, city-wide multiple use concept rather than attempting to adopt several different concepts on a smaller scale. This evaluation (to adopt a single multi-use rather than is based on the capacity of Lafayette's institutional system to service and sustain an additional administrative element, and the extent of service and support available to Lafayette through various and diverse agencies which assist local communities. A multiple use concept that is particularly compatible with the conditions in and around the City of Lafayette is the concept of incorporating stormwater management facilities with parks, recreation, and open space objectives. The idea of placing bikeways along drainageways, or having stormwater detention ponds perform the additional service of a pocket park is not a new concept. In many communities however, these multiple uses are generally adapted to, or "tacked on" to the runoff management facilities without examining city-wide plans and goals for recreation. This practice of merely tacking on recreational facilities to stormwater management facilities can result in recreation facilities such as bikeways and parks being created and implemented in a haphazard and unprogrammed manner. A particular hazard associated with this response type action is that each development could implement recreational uses for drainage facilities that do not coordinate with the facilities created in an adjacent development, or with the plans and goals of the community on a city-wide scale. The possibility of this condition occurring is enhanced by the policy of requiring each new development to manage its own stormwater within its own

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boundaries. Without a city-wide plan to direct developers in what kinds of recreation facilities would benefit the city the most, it is highly likely that the facilities provided will be designed for the potential users of the development and not necessarily for the benefit of the residents of the entire community. Such a responsive action strategy can lead to a recreation/ drainage system of individual parts or elements which lack a community-wide continuity. Such an unprogrammed system can become cumbersome and difficult to administer and sustain. Eventually such a system can result in the failure of the single, city-wide multi-use concept which can result in the labor intensive management practice of attempting to administer and service many individual parts of a system rather than administering a single, integrated and coordinated system. • • • THE CONCEPT INCORPORATING PARKS AND RECREATION OBJECTIVES AND FACILITIES WITH STORMWATER MANAGEMENT STRUCTURES. The single, city-wide multiple-use concept of using the lands required for stormwater management to fulfill parks and recreation goals and objectives is particularly suited to the current natural, social, and institutional conditions existing in and around Lafayette. The city's institutional system is staffed by knowledgable and competent people who are aware of the support system's capabilities and limitations. In addition, the staff is, at the present time, in an aggressive planning for the future mode. The city has a set of planning documents which, in general, have reasonable and manageable objectives and goals which provide a good starting point for future planning and document revision. A particularly strong influence in determining the multiuse concept of integrating stormwater management facilities with parks and recreation obiectives were the views 18

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and opinions of the residents. The residents expressed a desire for additional narks and recreation facilities through their response to the citizen survey and through their local elected officials. The views of the people in this matter are substantiated in the findings documented in Lafayette's Parks, Recreation, and Open Space Plan which states that Lafayette has a deficit of parks and recreation facilities based on National Recreation and Parks Association Standards. This present situation regarding parks and recreation facilities has been recognized by the elected officials of the city and they have responded by supporting parks and recreation plans for additional facilities and the renovation of existing facilities. The present stage of development and gl'owth in Lafayette offers a pl'ime opportunity for integrating stormwater management facilities parks and recreation facilities in the development planning and design stages rather than attempting to retTofit the concept to facilities that have already been constructed. The initiation of this concept at this particular stage of the city's development and growth allows for aggressive planning processes which begin to determine uses and forms rather than responsive planning which attempts to respond to the uses and forms which have already been determined and implemented. CONCEPT DEVELOPMENT The first step in developing the concept of combining parks and recreation uses with stormwater management facilities was to examine the stormwater management plans for Lafayette. As mentioned earlier, the two major drainage plans for the City of Lafayette are: l."City of Lafayette and Surrounding Unincorporated Areas of Boulder County, Colorado Storm Drainage Design and Technical Criteria." 2."Major Basinwide Planning City of Lafayette/Boulder County Phase B Development of Preliminary Plan."

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The two documents combined result in a management s ystem that combines the older stormwater management strategy of expedient conveyance o f runoff to the major drainage way with the new management strategy of collecting, detaining and then conveying the runoff water to the major waterway serving the community. Figure #8 is an abstract diagram of the management s ystem which results from the combination of these two plans (Technical Criteria and Phase B Preliminary Plan). The old management strategy of expedient conveyance of runoff has been maintained in those areas of the city that were developed prior to the adoption of the Technical Criteria. . . 8 ... { • • ..,-. . AI. . A . r . . : r. . '. ' . . .. , . .. L . 11' , ,. .. . :6-4• ... \' . . . . . . . ' .. , . . . \. .. . f'PIOII-111 D -m I f ffl't-1 FIG. 8 ABSTRACT-LAFAYETTE STORMWATER MANAGEMENT SYSTEM (FUTURE) This strategy however, onJy applies to existing land uses; development in the ol er part o f town which increases tne levels of runoff must take measures to manage that adaitional runoff! In the newer developed areas of the city the management strategy of collecting, detaining, and then conveying runoff water is mandated b y the Technical Criteria. Consequently, the newer areas o f 20

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the city will have detention ponds and the older sections of the city will not have detention ponds until the older area redevelops. The significance of this is that the older parts of the city will not have detention pond open spaces which can also be used for park space. The lines designated as conveyance structures in figure #8 are abstracts of those structures proposed in the Phase B Preliminary Plan; many of these structures do not, as yet, exist. As can be seen in figure #6, without these conveyance structures, which are designed to serve the entire basin, the water flows through the city in a generally unmanaged and unprogrammed way to Coal Creek. • • • FACILITY TYPES The next step was to define the types of stormwater management facilities used in Lafayette in order to determine an appropriate recreation multi-use, Figures SA and 8B briefly outline the th7ee types of management facilities in Lafayette, The corrective facilities are those drainageways proposed in the Phase B Preliminary Plan which are designed to mitigate the flooded area hazard which currently exists in Lafayette. Existing facilities are those facilities that are already approved for construction, or are currently under construction, or have already been completed. Included in this category is Coal Creek and its related floodplain. The final category, future facilities, are those drainage facilities that will be implemented with future developments. The significance of this categorization is that a recreational and parks program will have to be designed which will respond to these facility types in such a way as to provide a comprehensive system; if the single, city-wide multi-use concept is going to work. The recreation and parks program will have to integrate with all of the facility types in order to be effective.

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FIG. SA LAFAYETTE DRAINAGE FACILITY TYPES 22

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N LJ STORHWATER MANAGEMENT FAClllTIES TO BE EXJ\IoiiNED FOR POSSIBLE MULTIPLE USES fACILITY TYPES -------CORRECTIVE FACILITIES EXISTING FACILITIES FUTURE FACILITIES ACTION BASED ON FACILITY TYPES MITIGATE THE DEFINED 100 YEAR FLOODED-AREA HAZARD CREATED BY DEVELOPMENTS CONSTRUCTED PRIOR TO IMPLEMENTING: "STORH DRAINAGE DESIGN & TECHNICAL CRITERIA. " ADAPTATION OF DRAINAGE FACILITIES nr-bEVELOPHENTS ALREADY: APPROVED FOR CONSTRUCTION UNDER CONSTRUCTION COMPLETED DEVELOP AlTERNATIVE USES FOR ------THE-cOAl CREEK FLOOOPLAN DEVELOP GUIDELINES FOR FUTURE FACILITIES WHICH WILL INCREASE THEIR POTENTIAL FOR MULTIPLE USE FIG. 88 FACILITY TYPES & ACTION FLOWCHART HOOE Of ACTION RESPONSE RESPOND-TO EXISTING PLANS & CONDITIONS INITIATIVE lN1Tiiftltr FUTURE DRAINAGE FACILITY DESIGNS

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In summary: the natural, social, and institutional elements in Lafayette are developed to a point where all that is required for concept implementation is to bring these elements together in a manner which is more programmed and coordinated than the elements are at the present time. In other words, the basic pieces necessary for the success of the multi-use concept exist already, all that is required now, is to synthesize those pieces into a coordinated and programmed whole. • • • 24

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CONCEPT SYNTHESIS Synthesizing the concept of integrating park and recreation facilities with stormwater management facilities was conducted by constructing a set of informal overlay maps (figures 9 15). The maps were drawn and assembled primarily as an inventory and analysis tool in order to understand the location, connections, and interrelationships between the natural and social environments in and around Lafayette. Figure 9 is a composite map which overlays the existing ditches and creeks combined with the drainageways proposed in the Phase B Preliminary Plan with the city limits and Lafayette's planning area boundary. This map illustrates the relationships that exist between the city and the existing and proposed stormwater conveyance structures. The proposed drainageways illustrated in figure #9 demonstrate how the proposed drainageway routes penetrate the central core area of the city and connect that central area with Coal Creek. The proposed drainageways shown in figure #9 also illustrate how the major drainage basin defined in figure #10 is to be drained. A major drainage issue manifests itself at this point. The Phase B Preliminary Plan specifically addresses the drainage issues within the defined major drainage basin boundary (see figure #10). However, recent city growth patterns are extending development beyond this major basin boundary and into adjacent drainage basins. Research efforts were unable to supply documentation which specifically defined drainageway routes and capacities in these adjacent drainage basins. Development in drainage basins without a clear understanding of natural drainageway routes and capacities can lead to drainage problems in the future. A clear understanding of natural/existing drainageways can avert such problems as inadvertent obstruction of these as yet undefined drainageways by developments, or fixing detention pond release rates which may result in runoff quantities being released into drainageways which do not have enough capacity to convey these amounts without bank overtopping or similar effects. Either of the previously described situations can lead to another flooded area condition similar to the one that exists in the basin defined in the Phase B Preliminary Plan. 25

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••••••••••• ----------PROPOSED DRAINAGEWAY -PHASE B STUDY DITCHES/CREEKS PLANNING AREA BOUNDARY CITY LIMITS (1983) FIG. 9 DITCHES, CREEKS, & PROPOSED DRAINAGEWAYS

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CITY Of LAFAYETTE AND SURROONOING BOULDER COUNTY lEGEND sw,_...._, Drainot• Sub-llooift _.,,, t:t::: ttt'io::"a,IOO FIG. 10 MAJOR DRAINAGE BASIN & SUB-BASIN BOUNDARIES Original base map from, "Major Basinwide Planning City of Lafayette/Boulder County Phase B Development Plan.• Camp, Dresser, & McKee 19BO.

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28 DEVELOPMENT CONSTRAINTS The next map, figure #11, overlaid the general constraints to large scale development and related them to the drainageway routes proposed in the Phase B nary Plan. This map is significant because it illustrates that the general direction of future city growth is likely to be in a generally northerly direction. A significant point illustrated by this map is that a sizable area of the city is restrained from development primarily because of two elements; 1. subsidence hazards which are a result of past underground mining activities, and 2, areas which are already developed, A point of overriding importance is that the drainageways proposed in the Phase B Preliminary Plan (the implementation cif which is vital to alleviating the existing flood hazard in Lafayette) are routed through areas which are not likely to develop. Routing these drainageways through areas not likely to develop is an especially significant point if the city is relying on dedicated land from developers for acquiring land for the proposed drainageways. If land acquisition for these drainageways is dependent solely upon developer dedication it is unlikely that the implementation of the Phase B Preliminary Plan will progress in an expeditious and programmed manner. • • •

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SUBSIDENCE HAZARD DEVELOPED AREA I I I I I I I I I STEEP SLOPES FAULT LINE ----PROJECTED FAULT LINE PLANNING AREA BOUNDARY ---CITY LIMITS (1983) • • • • • • • • • • PROPOSED DRAINAGEWAYS FIG. 11 CONSTRAINTS TO LARGE SCALE DEVELOPMENT

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30 DESTINATION POINTS The map shown in figure #12 relates possible destination points to the city limits and planning area boundary. There are two types of destinations programmed into this illustration. The first are destinations that do not yet exist, but with future development are likely to become areas of public activity. These possible, future destinations are primarily based on the existing water features located to the north of the city and the assumption that the city will find acquisition of these sites forpublic use a desirable objective. The second category of destinations are those sites that have already been developed for general public use. Another land area that would likely be a desirable addition to parks and open space lands is the floodplain adjacent to Coal Creek. • • •

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DESTINATIONS POSSIBLE/FUTURE EXISTING PLANNING AREA BOUNDARY CITY LIMITS (1983)

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32 DESTINATIONS a DEVELOPMENTS Figure #13 is an overlay map that relates the destinations with the major existing developments in the Lafayette area. As can be seen on the map, there exists a close relationship between the developed areas and existing and proposed destinations. This is a fortunate development since the distances between the developed sites and possible destinations is relatively short. The short distance relationships can lead to easier planning and design of connecting links between developments and destinations. • • •

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I I r-----+ I I --+----i + L __ _t N POSSIBLE DESTINATIONS DEVELOPED DESTINATIONS DEVELOPED AREAS ---PLANNING AREA BOUNDARY ----CITY LIMITS (1983) FIG. 13 DESTINATIONS RELATED TO DEVELOPED AREAS

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34 DRAINAGEWAY RELATIONSHIPS Figure #14 (is also figure #5) is a composite overlay which illustrates the relationships which exist between 1. developed areas, 2. destinations, 3. creeks and ditches, 4. drainageways proposed by the Phase B Pre liminary Plan. At this point the relationships and . connecting links that could be developed based on multiple use of drainage structures becomes more evident and increasingly promising. • • •

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-, ( } DEVELOPED AREAS ..... .,/ PLANNING AREA BOUNDARY --CITY LIMITS (1983) • • • • •• • • • •••• PROPOSED DRAINAGEWAYS ---CREEKS/DITCHES POSSIBLE DESTINATIONS DEVELOPED DESTINATIONS FIG. 14 PROPOSED DRAINAGEWAYS, CREEKS, & DITCHES AS RELATED TO DEVELOPED AREAS & DESTINATIONS

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36 SPECIFIC RELATIONSHIPS MAP a CONNECTIONS MATRIX Figure #15 is a similar overlay to figure #14 with the exception that it was developed to a more specific scale. This specific scale began to demonstrate the close proximity relationships that exist between drainageways and more specific public sites. At this point the multi-use concept becomes more specific. The proposed drainageways can also be used as alternative transportation links (trails) between desirable destinations. The matrix in fig. 16 illustrates the proximity relationships between the drainageways (possible connecting links) and destination points, The facilities, both existing and proposed, are related to appropriate and feasible alternative recreational uses. • • •

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'lAP N O . .. / / \ .. / \ y . . . • I • ••• 1 ... ; & ,.•• ,• \2../J •••••••••••• ,. "'---I . LAF A VETTE /. : .-:-:-;-:--:-:-: • • • • ..VI\ • • • • • • • , . ---PLANNING AREA BOUNDARY ----ciTY LIMITS (1983) -CREEKS/DITCHES • • • • • • • • • PROPOSED DRAINAGEWAYS FACIUTY RELATIONSHIPS

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MAP fl:l. FACILITY 1. ORAINAGEWAY 11 2. DRAINAGEWAY ;2 3. DRAINAGEWAY 13 4. DRAINAGEWAY 5 . ORAINAGEWAY ;s 6. DRAINAGEWAY 7. DRAINAGEWAY w7 8. COAL CREEK & FLOODPLAIN 9 . PARK SPACE GLENWOOD & LUCERNE DRIVES 1D. LAFAYETTE CITY PARK 11. LAFAYETTE MIDDLE SCHOOL 12. LAFAYETTE ELEMENTARY SCHOOL 13. PARK SPACE ELEMENTARY SCHOOL 14. COMMUNITY SERVICES 15. RODEO GROUNDS 16. WANEKA RESERVOIR 17. DRAINAGE AREA-WANEKA RESERVOIR 18. FUTURE SCHOOL SITE -DELPHI OR. 19. PARK SPACE CARlA OR. & CENTAUR VILLAGE OR. 2D. DRAINAGE AREA-HERMES ST. 21. ORAINAGEWAY CARlA OR. TO S. BOULDER RD. 22. DRAINAGE AREA S. BOULDER RD. & ATLANTIS CIR. 23. DRAINAGE AREA S. BOULDER RD. 24. DRAINAGE AREA S. BOULDER RD. TO ILLIUM DR. 25. CENTAURUS HIGH SCHOOL FACILITY STATUS proposed proposed proposed proposrd ro osrd proposPd natural area natural area maintained maintained maintained maintained maintained natural area natural area natural area natural area natural area natural area natural area natura 1 area natura 1 area natura 1 area "'a i ntai ned 26. ORAINAGEWAY SW. CORNER CENTAURUS HIGH TO CENTAUR CIR. natural area 27. ELEMENTARY SCHOOL-CENTAUR VILLAGE maintained 28. PARK SPACE CENTAURUS ELEMENTARY SCHOOL, STRIP TO NW. natural area 29. PARK SPACE CENTAURUS ELEMENTARY SCHOOL, STRIP TO SW. natural area 30. COAL CREEK PARK SPACE U natural area 31. LAMONT DOES COMMUNITY PARK maintained POSSIBLE FACILITY USE CONNECTING ll fiK (NON-MOTOR! ZED RECREATION TRAIL) PARK SPACE STRIP pnqr & CONNECTING FIG. 16 FACILITY CONNECTIONS 38

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The "possible use" categories listed in the matrix of figure #16 were selected on the basis of the following: • The goals for parks and recreation facilities as they were defined by the residents in the Lafayette citizen survey • The existing and proposed stormwater management facility types in and around Lafayette In general there are two basic types of facilities in use for managing stormwater runoff in Lafayette; 1. dry detention structures and 2. conveyance structures (drainageways). These two structure types prompt two different recreational concepts (see figure #17). Those facilities which are designed to store and release runoff water at a controlled rate can be used for public activity places such as small pocket parks, playlots, and etc. The appropriate uses for these structures will depend upon their size, configuration, location, and the type of recreational need determined by the neighboring residents (playlot, basketball court, etc.). The second type of stormwater management facility is the drainageways which are intended to convey water from the detention ponds (activity places) to Coal Creek. These conveyance structures can be easily adapted for trail use which can provide the residents of Lafayette with a system of connecting links that are separate from those links designed for motorized vehicles. By extending the basic idea of detention facilities as activity places and drainageways as connecting links, and relating this concept to the specific stormwater management facility types in Lafayette, three recreational multi-use concepts can be formed. The three multi-use concepts are based on the land areas used for stormwater management facilities and are categorized below: 39

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40 • Activity Places/Dry Detention Ponds: those areas which are typically used for ing runoff water from storms having a percentage chance of recurring every 10 or 100 years. These spaces can generally be easily adapted for park or al type activities such as a basketball court, playlot, etc. (see figure #18) • Connecting Links/Drainageways: these are usually narrow strips of land that contain drainageways which are particularly adaptable for use as trails connecting various points of public interest, (see figure #19) • Combination Activity Place and Connecting Link: this type of recreational use is adaptable to those areas that are relatively wide and long which have a conveyance structure running through them. An example of this type of use would be a strip park which has a drainageway/trail running through it. (see figure #20) • • •

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UNOFF MANAGEMENT AND USE TERNATIVES RUNOFF MANAGEMENT USE DETENTION FACILITIES WET /DRY RETENTION FACILITIES OPEN CHANNEL DRAINAGEWAYS MULTIPLE USE CONCEPTS ADAPT UNDERUSED SPACES ACTIVITY PLACES CONNECTING LINKS BETWEEN DESIGNATED ACTIVITY PLACES COMBINATION OF ACTIVITY PLACES & CONNECTING LINKS (I.E. A STRIP PARK WITH A BIKEWAY CONNECTING ACTIVITY PLACES) EXA.'olPLES OF POSSIBLE ADDITIONAL USES PLAY LOTS POCKET PARKS NEIGHBORHOOD PARKS DISTRICT PARK REGIONAL PARK WILDLIFE SANCTUARY NEIGHBORHOOD GARDENING BIKEWAYS PEDESTRIAN PATHS EQUESTRIAN TRAILS FITNESS TRAILS INTERPRETIVE TRAILS PLAYLOTS STRIP PARKS INTERPRETIVE TRAIL BIKEWAY WILDLIFE SANCTUARY FIG. 17 RUNOFF STRUCTURE TYPES/MULn-USE CONCEPTS 41

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FIG. 18 DETENTION BASIN IN RESIDENTIAL DEVELOPMENT FIG. 19 DRAINAGEWAY /TRAIL THROUGH RESIDENT AIL DEVELOPMENT FIG. 20 r'T"Cf"J!.MJ L-lNE!-6 F1c':::41-1f OF" AAI orroM"LJN rrY rtl,_ .. .-STRIP PARK WITH TRAIL/DRAJNAGEWAY THROUGH RESIDENTIAL DEVELOPMENT

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TRAIL CONCEPT DEVELOPMENT An important element in the recreational multi-use concept is a system of trails which link together the various points of public interest on a city-wide scale. There are, in general, two basic types of trails; the destinational trail and the recreational trail. Each trail type has its own group of user types, and its own set of design objectives. (see figure # 21) The destinational trail, as .its name implies, is generally used to travel from one point to another with the primary user activity being located at either end of the trail. The use pattern for this type of trail usually requires the user to use the same trail for both traveling to the destination and returning from it. An example of this trail type would be a trail between a development/neighborhood and a ballfield located at some distance from the neighbo-rhood, The tTail would be used to get from the neighborhood to the ballfield where the primary reason for trail use (playing ball) is conducted. When the ball game has ended the user retraces his or her route, using the same trail, back to the neighborhood in which he or she resides. The significant difference between the destination type of trail and the recreational type of trail is that the primary use activity on a recreational trail is the activity conducted on the trail itself. In general, the successful recreational trail is usually one that returns on itself ... a loop. This loop type of pattern adds interest to the trail by not requiring the user to retrace his or her route in order to return to the point of origin. This type of trail, looping pattern, is particularly suited for use as fitness trails, interpretive trails, jogging, or leisure biking or strolling. Being designed as a loop, the user can always return to the .point of beginning without retracing his or her steps. Although two trail types have been described above, this is not to say that users cannot or will not use destinational trails for recreational purposes or that recreational trails should not have destinations. But, the categorization does indicate the primary use and user groups associated with designing a trail system. A trail system that is designed to meet the needs of both user types (recreational and destinational) is likely to be a system that affords its community the most benefit. 43

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44 Residents of the City of Lafayette are fortunate in that the locations of the primary destinations and the rout-ing of the proposed drainageways are very compatable geographically and they can easily accommodate a combination of trail types (recreational and destinational) in an integrated manner. Figure #22 is a conceptual illustration of the combination recreational and destinational trail system. In the combination type trail system destinational routes and recreational routes are interconnected and progressively build on each other. This type of design serves a larger and more diverse user group than either the destinational trail or recreational trail alone. A first step in implementing a combination trail system is to define the route or routes to be used for destinational trails. This is accomplished by first determining the base location of the primary user group (i.e. the neighborhood) and the desirable destinations (i. e . park, ballfield, shopping area, etc.) and connecting the two with a trail that is adjacent to a drainageway. After the destinational trail routes have been planned, the recreational trail routes can be added to the destinational trail framework as a system of loops or trail moduals. Planning a city-wide trail system using the methods described above allows for phased implementation within the context of a large scale strategy. Adding loop trails as modules to a trail system, for example, is a concept that is highly compatable with the planning concept of phase implementation. • • •

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• • • 111!-iO' .. .. aW!" US. "NN.-) !"4ft A. Mt!Uf" • • ''floe 1l'WI.-I!S P6 1tl fi'\?1-1 t::> A fe-ND II f'tl!4 I "fAjijl-6 '$NP'f"O &e. ' bfr!OUP .lq" A AN .A&f!VIf'l # l'Mlh 14-e f\..t.Nt.Je9 ,..Of\. .... 6t/rPUf' FIG. 21 TRAIL CONCSJIS • * .. ... '1-::.......:...-.IOf!VI!"( •. 11' AN INPMPUIIJ-LAIP!> J i e , 1-lNI'--11E'-IN • 121 Of"e!-1 If te!Ntffr 4 5 FIG. 22 COMBINED TRAIL CONCEPT

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46 INSTITUTDNAL INTERRELATIONSHIPS The final analytical step in this phase of the project examines the possible institutional interrelationships that might exist if the concept of incorporating recreation objectives and facilities with stormwater management facilities is adopted. The concept itself is compatable and easily integrated with the following planning and institutional framworks. Figure #23 is a matrix and flow diagram which illustrates the interrelationships between the various planning and institutional elements that are involved with implementing the multiuse concept of incorporating stormwater management facilities with recreation obiectives and facilities. Diagram A of figure #23 illustrates the connections between the concept and the various elements of the urban system with which it will interrelate and the extent of that interrelationship. As the diagram indicates, the concept has anintegrating effect on the following elements: • The Phase B Development of Preliminary Plan • The Storm Drainage Design and Technical CriteTia • The Transportation System • Land Use • Parks, Recreation and Open Space The matrix illustrates the following interrelationships: 1. Various elements and the multi-use concept 2. The interrelationship between the elements themselves 3. The extent of the interrelationships between the elements, and the elements as they relate to the multi-use concept

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...... -••••ttl f1,&iW 47 FIG. 23 INSTITtmONAL INTERRELATIONSHIPS

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48 Diagram C of figure #23 is an illustration of the connections and interrelationships between the various elements and the multi-use concept. The diagram illustrates that there will be strong connections between the staff positions responsible for land use, parks, recreation and open space, and public works. A moderate connection exists between land use and the technical criteria. This moderate connection reflects the situation that the technical criteria determines to a moderate degree, areas of open space which are a result of implementing dry detention ponds for the purposes of stormwater management. The slight connection between land use and the Phase B Preliminary Plan indicates that a specified amount of land and its location are already programmed or at least should be programmed into land use. There is a strong between land use, the multi-use concept, and the parks system which illustrates the impact of the concept on both development site planning and the citywide concept of incorporating recreational objectives and facilities with stormwater management facilities. There is anobvious strong connection between the multiuse concept and the parks system since the concept is particularly concerned with parks, recreation, and open space objectiyes and facilities. There is also a strong connection between the Phase B Preliminary Plan and the Technical Criteria. This strong connection illustrates that the two documents are intended to be used in conjunction with each other. The strong connection which exists between the multi-use concept and the Technical Criteria illustrates the space making influence the Technical Criteria has by directing each development site to implement dry detention ponds as stormwater management devices. The concept suggests that those detention facilites which are suitable be utilized as public acticity places. There is a strong connection between the concept, the parks system, and the Phase B Preliminary Plan. This three way connection illustrates that the system of connecting links (trails) is largely dependent upon the implementation of the conveyance structures as they are proposed in the Phase B Prelimi nary Plan. The slight connection between the parks system, the multi-use concept, and the transportation system illustrates the influence of the proposed trail system on the transportation plan and how strongly the proposed multi-use concept will affect the transportation system. As the diagrams illustrate, there are

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likely to be three staff positions with a relatively high degree of involvement in the multi-use program. These positions are likely to be those that are involved with the following UTban elements; city-wide planning and individual development site planning, parks, recreation, and open space, and public works. The majority of the involvement will be between the city-wide planning and development site planning staff member/members and the staff member/members responsible for parks, recreation, and open space goals and facilities. • • • SUMMARY Many of the stormwater management structures in Lafayette are underutilized and Those underdeveloped or underutilized land areas offer opportunities for improving the quality of life forthe residents of Lafayette as well as improving the visual environment of the entire city. Many of the existing stormwater management facilities in Lafayette are beginning to deteTiorate because of erosion and sedimentation. Such deterioration can result in increased flooding hazards with consequent property damages. Current stormwater management strategy is generally directed by two documents: • "City of Lafayette and Surrounding Unincorporated Areas of Boulder County, Colorado Storm Drainage Design and Technical Criteria." • ''Major Basinwide Planning City of Lafayette/Boulder County Phase B Development of Preliminary Plan." The Technical Criteria manual is, in general, a policy document which determines that each new development resolve its stormwater drainage issues within its own development boundaries. This usually results in each development having its own dry detention basin and influent conveyance structures. 49

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50 A flooded area hazard exists in the city of Lafayette at the present time. This flooded area hazard can be mitigated by the implementation of the Phase B Prelimi nary Plan. The Phase B Preliminary Plan is in the preliminary planning phases of This status results in the following; • A continuation of the flooded area hazard as illustrated in the Phase B Development Plan (see figure #3) • A city-wide drainage system that essentially has stormwater collected in areas which are located at some distance removed from where they are intended to be discharged (Coal Creek) with no programmed means conveying these collected waters through a system of conveyance structures. The conveyance structures proposed in the Phase B Preliminary Plan are the missing link that joins the collected water at one end of the system with the major drainageway (Coal Creek) at the other end of the system, Lacking this missing link, stormwater will con tinue to flow from the developed areas, through the city, to Coal Creek in an unmanaged and unprogrammed manner. The current status of the Phase B Preliminary Plan offers the opportunity for multiple use concepts for stormwater management structures to be implemented at the structure design stage which will result in structures that are designed for multiple use from design inception to final construction. The Phase B Preliminary Plan resolves drainage issues within a single, defined, major drainage basin. Development in Lafayette is currently beginning to extend beyond this basin boundary and into adjacent drainage basins. Developing in drainage basins without a clear understanding of the drainage patterns can result in obstructing natural drainageways, overloading natural drainageways, and similar problems. This can result in flooded area hazards and similar severe runoff impacts in the future.

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Several reaches of the conveyance structures proposed in the Phase B Preliminary Plan are routed through areas that are unlikely to be developed. If the city pursues a policy o depending on developer dedication for land acquisition for these runotf structures, then it is likely that the implementation of the Phase B Prelimi nary Plan will proceed in an expeditious and pPogrammed manner, There is a very close proximity relationship between public activity areas (parks, schools, etc.) and the conveyance structure routes proposed in the Phase B Preliminary Plan. Such a close proximity relationship is very compatible with the concept of conveyance structures serving additional recreational services such as trails, strip parks, and etc. A single city-wide multi-use concept is proposed for the city of Lafayette as opposed to several, smaller scale concepts. This suggestion is based on the idea that managing and servicing one large system is generally more efficient than trying to service several different concepts and their related systems, A single, city-wide concept which is highly compatible with the natural, social, and institutional environments in Lafayette is the concept of incorporating parks, recreation, and open space objectives and facilities with the stormwater management facilities. The benefits that can be gained by implementing this concept are as follows: • An expanded funding base for drainage facilities by combining drainage ties with parks, recreation and open space funding sources • An enhanced community visual image • Additional parks and recreation facilities for community residents • A recreational and destinational trail system which minimizes conflicts between useTs and motorized traffic

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52 • A more thorough integration of two tial planning elements, drainage and recreation, into the overall urban design The relationships between the proposed Phase B Drainageway routes and trail planning objectives combined with the locations of existing public activity places in Lafayette allow for a combined destinational and recreational trail to be implemented with relative ease. The types of trails and the suggested design process permit phased implementation of the trail system based on local need and available funding. The multiple use concept of combining park and recreation facilities and objectives with drainage facilities is a concept that is very 'compatible with present and future development. The city staff persons most likely to be involved with concept implementation and operation are as follows; 1, Those staff members concerned with planning 2, Those who are involved with development site planning 3, Those concerned with recreation and open space 4, Those who are involved with public WOTkS The two staff positions that are p-rimarily involved are those positions in planning and parks, recreation and open space. • • •

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'• ' .. 1 t ' ; ! .. : < : 1.' -' . '. , > I . ' , ' ' ,'1 ... MAINTENANCE ROAD/RECREATIONAL TRAIL -z 0 t3 w en

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TRAIL ROUTE ALTERNATIVES This section contains various alternative uses for underdeveloped stormwater management areas already existing in the city of Lafayette, The alternatives are presented as suggestions only, and not necessarily as a hard and fast program. These suggestions are intended as a menu of alternatives which are compatible with stormwater management facilities in Lafayette. The final selection of precisely which activities should be implemented at specific sites is left to those persons who know their recreational needs the best ... the residents of the surrounding neighborhoods and the citizens of Lafayette. Many of the ideas contained in this section are purposely intended to be far reaching and ambitious in scope and scale. The intent including far reaching and ambitious ideas is to provide a starting point from which constructive planning and programming can begin. The purpose of setting a starting point which is comprised of a set of goals which at first are perceived as unattainable is to provide a yardstick or measure against which actual plans and programs can be compared. Ambitious goals also provide the basis of relevant discussion and idea exchange_which are the first steps in programming, design, and implementation. THE TRAIL SYSTEM In keeping with the concepts and ideas formulated earlier in this document, three trail systems are illustrated in this section. Each system is progressively more ambitious than the previously suggested plan. Each suggested plan can stand on its own and can be implemented as illustrated. But, the primary intent behind illustrating the three plans is to stimulate alternative ideas, and thereby prompt action toward implementation of a system. Although each of the three suggested systems are different in the number of miles of trails or in their trail routes, they are all designed to respond to the same objectives. 53

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54 All three systems contain both destinational links and recreational loops. The destinational links accompany drainageways which connect to existing and future major public use facilities. The recreational trail: loops are generally kept to a length of two miles OT less which is the recommended length for recreational types of trails. These loops are generally interconnected in such a way that at least one leg of the loop is shared with an adjacent trail loop. The points at which these loops intersect have, where practicable, been placed in areas that are presently in the public domain. Those trail intersections shown which are not as yet in the public domain pTovide an incentive for the city to obtain these areas through open space dedications, or similar means of acquisition. The Coal Creek floodplain plays a major role in all three of the suggested plans. The floodplain area has long been recognized by the residents of Lafayette as a viable and valuable community resource. The floodplain riparian area has been designed into the three systems in order to provide access to this area and thereby enhance its use potential for the city's residents. Another common element shared between the three plans is that of providing regional trail connecting links. The locations of these connecting links have been designed to take advantage of the trail routes proposed in the State of Colorado Non-motorized Trail Plan. Most of the trail proposed in these illustrations which is routed along Rock Creek has already been designated as a state non-motorized trail. The trails suggested in this section are also designed to provide convenient connections to surrounding communities. The specific communities towards which those connecting points are oriented are; Louisville to the west, Broomfield to the south and Erie to the north.

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A primary objective in the design of these suggested trail systems was to utilize the drainageways proposed in the Phase B plan in order to provide a system that would minimize the use competition between motorized and non-motorized transportation modes. For the most part? this objective was achieved. The only areas which utilize streets or roads as part of a trail route are those trail links where alternative routes were not available? and using a street was the most reasonable way of providing a necessary trail link in order to complete the trail system. • • • FACILITY INVENTORY & ALTERNATIVE USE MATRIX The Facility Inventory and Alternative Use Matrix (illustration #24) consolidates and programs both existing and proposed stormwater management and public use facilities with compatible alternatives. This menu of multiple use alternatives was assembled based on selected cTiteria which responded to the identified needs of Lafayette. A primary consideration when selecting alternatives for stormwater management facilities is the compatibility between the alternative and the drainage facility, The stormwater management aspects of the facility should not be impared by the implementation of the selected alternative, nor should the facility sustain excessive damage from being temporarily inundated by runoff. An additional consideration that was used in the assembly of the menu of multiple use alternatives was the ability of the multi-use alternative to be adapted to both, 1) existing stormwater management facilities and, 2) the construction criteria for future stormwater management facilities. Multi-use alternatives that would require extensive modification of either existing stormwater management facilities or major changes in the construction criteria as detailed in the technical criteria manual has been deleted from the menu of multi-use alternatives. 55

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56 A final major consideration in the selection of multiuse alternatives was citizen input. Multi-use alternatives were selected on the basis of the views of the residents as they were expressed in 1) the Lafayette Parks and Recreation Plan and, 2 ) the Lafayette C itizen Survey. These documents expressed the need for additional recreation facilities which are appropriate to the teen/young adult age group. The menu of multi-use alternatives was assembled in order to respond to this expressed recreational need. • • • MATRIX CATAGORIES FACLITY The facility category of the matrix describes the areas of major importance selected for this study. The major facilities selected or this study are broadly defined as follows; • Major storrnwater management facilities both existing and proposed • Major public use areas such as existing parks • Undeveloped park lands • Major detention basins • Schools The existing and proposed school sites are listed primarily for illustrating probable trail destinations or activity nodes. No suggestions have been proposed, in the matrix, for recreational activities on school sites even though the existing schools have some recreation facilities. The reason recreational activities at school sites have not been included in this program is because the school system and the city's parks and recreation department are separate organizations. At the present time there is no formal agreement between the city and the school system which addresses use, maintenance, or repair of school recreation facilities.

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The facilities category in the matrix is intended to be used in conjunction with the map; "Major Stormwater Management and Community Facilites Inventory." The facilities listed under this matrix category are numbered/keyed to the facilities inventory map for convience. • • • STAnJS The status category of the matrix categorizes the status of the existing/proposed facilities. A brief explanation of each sub-ca tego'ry is lis ted below. COAL CREEK FLOODPLAIN A facility with a dot in this sub-category indicates that the corresponding facility is located in the Coal Creek Floodplain, CORRECTIVE FACILITY A facility with a dot in this sub-category indicates that the corresponding facility is one which is for mitigating the existing flooded area hazard 1n Lafayette. Such facilities are detailed in the Phase B Development Plan. NATURAL AREA A facility with a dot in this sub-category indicates the current maintenance and upkeep of that area. Generally, facilities with this designation are land areas which are unimproved, not programmed for organized recreational use, and receive minimal maintenance and upkeep. Typically, natural areas represent underdeveloped park and recreation resources. PARK Facilities with a dot in this sub-category are those land areas which are currently the responsibility of the Lafayette Parks and Recreation Department. 57

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58 SCHOOL A facility with this designation represents existing and future land areas which are or will be the responsibility of the school district, Although schools and their recreation facilities are not a part of the city's recreation department area of responsibility, they are a recreational resource for the residents of Lafayette. • • • MULTI-USE ALTERNATIVES This major category is comprised of several sub-categories which illustrate the various use alternatives for stormwater manage.ment facilities inventoried, The first four 1) activity node, 2) trail access point, 3) trail link and 4) link and node are broad categories which classify the multi-use alternatives in a general way. A brief description of each category follows: ACTIVITY NODE This classification indicates that the facility land area can or should be used for activities conducted at a specific place, Activity nodes are typically areas that users travel to, and use whatever facilities exist at that location. TRAIL ACCESS POINT Trail access points are generally those outlets which allow stormwater runoff to be conveyed from areas within a development to the major drainage facility serving the development. The outlets usually are narrow strips of land which are generally too small for use as activity nodes or parks. The outlets can, however, serve a useful function as trail access points to those trails which are located adjacent to drainageways routed behind residences, between property lines, or are generally inaccessible for similar reasons.

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TRAIL LINK Facilities with this designation are those facilities which are best suited for use as trails. Such facilities are usually on land areas that are relatively narrow, and being narrow offer little opportunity for use as activity nodes, or parks. LINK A NODE Facilities designated as link and nodes are those facilities whose land areas and configuration offer opprotunities for use as both trail links and activity nodes. An example of such a use would be a strip park that has a trail adjacent to a stormwater conveyance structure that is routed through the strip park. This multi-use alternative offers the opportunity for use as both a park and an integral part of the community-wide trail system. TRAIL TYPE The two trail types, leisure and destinational, listed under this the type of trail for which the listed facility is best suited, TRAIL USE ALTERNATIVES This sub-category describes appropriate uses for the suggested trails. The listed alterantives are briefly described below, BICYCLE These trails are generally longer or the trail routes are programmed in such a way as to connect to other trails and thereby allow users to ride for a variety of uninterrupted distances, The trails can be either destinational or recreational, 59

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60 JOGGING, FITNESS, NATURE, & INTERPRETIVE TRAILS This type of trail is generally designed for pedestrian use. Although such trails are designed primarily for the pedestrian user group, these trails can and should also be designed for use by other user groups such as bicyclists. Although each of the above listed trail types are very different, they share two important design elements ... their length and route layout. Typically, their length should be less than two miles, and the routes of such trails should allow the user to return to the point of origin without retracing his or her route. When the trails are examined from their length and routing perspective, these trails can be classified on the broader scale, as leisure type trails. An element that solidifies this leisure classification is that the primary user activity (reason for trail use) is conducted on the trail .. ,the trails are used for the activities which they provide the user, they are not designed for the primary use of traveling from one point to another. Although each of the above trials share fundamental design elements such as length, route configuration, and use profile, they are distinct from each other in the elements which accompany the trail itself. These distinctions are clarified below. JOGGING A jogging trail differs from the other trail types in that the user desires a trail whose route is uninterrupted by required stops such as street intersections and similar conflicts. The trail suTface should be relatively smooth and unbroken which allows the jogger to spend less time concentrating on the safety of his or her footing while jogging. An added factor in the design of this type of trail is that the trail should allow the user a range of visual experiences, and the opportunity to see and be seen by other people while jogging,

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FITNESS A fitness trail is typically a trail of shorter length and generally requires the installation of site structures. The trail type has, at programmed distances, stations that offer physical challenges to the user. At each station point there are generally two structural elements; 1) the obstacle intended to develop physical health and, 2) an informational element (generally a sign) which usually communicates to the user how the obstacle is intended to be used, In many instances tional information is provided the user such as desirable pulse rate, optimum amount of elapsed time from the start of the course, and similar data. The information communicated to the user generally takes two basic forms, 1) instructions on the use of the course and its obstacles and 2) feedback information which allows the user to evaluate his or her performance against a selected _set of standards. NATURE A nature trail usually relies on a sharp environmental contrast in order to provide user gratification. This environmental contrast is usually provided by a natural or natural-like setting which contrasts with the surrounding urban environment. This type of trail is usually routed through environments that are relatively unprogrammed. This is to say that the environments are usually allowed to develop and sustain themselves with little maintenance of the surroundings. INTERPRmVE Interpretive trails are trails that are intended to part information to the user about the environment surrounding the trail. Such trails can be routed throuah a range of environments :!;rom the natural to the The common element in this type of trail is the communication of information. Although the trails listed above are designed for particular uses and user groups, this is not to say that each t:ail will exclude the use of another user group, The C1ty of Lafayette has the opportunity to provide its residents with an integrated trail system which follows the city's existing or proposed stormwater conveyance facilities. The conveyance facilities are routed

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62 through a wide variety of environments which offers the unique opportunity to develop a wide variety of trail types which appeal to a wide variety of user groups. The selection of what trail type should be located in a specific area should be made with care, The trail type should be compatible with overall city plans, the environmental opportunities of the specific routes, and the desires of the users and residents of Lafayette. ALTERNATIVE NODE ACTIVITIES This section of the matrix suggests a menu of activities which are compatible with stormwater management facilities requiring relatively large land areas such as stormwater detention basins. The use alternatives proposed can usually be adapted to existing or proposed drainage facilities with a minimum of structural modifications to those drainage facilities. The majority of the alternative node activities are self-explanatory. However, in the interest of clarification the alternatives labeled; 1. green space, 2. open space, 3. natural area, 4. nature preserve, and 5 . screening are briefly defined below. GREEN SPACE These are defined for the purposes of this document to be those areas that are planted and maintained in order to provide open spaces which can be used for leisure activities. Such areas are sodded and planted with vegitation which usually require irrigation and maintenance activities such as frequent mowing and other plant care. These areas are intended to provide green spaces within the urban environment. Such spaces are intended for unprogrammed leisure use as well as enhancing the visual environment of the city.

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OPEN SPN:E. This type of space is defined for the purposes of this document, as open land areas surrounded by land areas of contrasting land use. These areas can be either green spaces or natural areas. The element between this classification and green space/natural area is that the lands are generally unprogrammed and permit leisure activities which are not organized by the city. A natural area is defined for the purposes of this document as open space land areas which receive a minimum of maintenance. Such areas are typified by the vegetation existing on the site such as those species commonly referred to as "native species." NA'IUE PRESERVE A nature preserve refers to natural areas which have been designated as areas that are set aside for the preservation and perpetuation of the animal and plant life which existed in the area prior to urban development. SCREENING Areas that are proposed for screening are areas that are relatively unsightly or present a discordant community image. The option for these areas is that if they are not developed for multiple use, they should be screened from public view. There are however, land areas listed in this sub-category which because of their size and configuration are more appropriately screened from view rather than going to the expense of attempting to adapt them for multiple use. PRIMARY USER GROUP This category defines the age group best served by the suggested multi-use alternative. Based on the research conducted for this study, the citizens of Lafayette have 63

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64 identified a need for additional recreation facilities which would serve the teen/young adult age group. As can be determined from the matrix, the majority of gested alternatives respond to the recreational need of that user age group. PARK TYPE The final section of the matrix identifies the potential park type for selected land aTeas. The stormwater runoff facilities in Lafayette permit a wide variety of park types to be integrated with a variety of drainage structure types. • • •

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CITYWIDE TRAIL PLANS To complete the multi-use program three suggested trail plans are illustrated. These trail plans are intended to be used in conjunction with the Facilities Inventory and Alternative Use Matrix in order to provide an integrated multi-use plan. (see figure 25 for trail comparison matrix) V'l >-3 ....., ...... t.:' 0 z: ... ..... z: ....., ... :I: -....., z: ... 0:: ..... ... 0:: I-0 3 z: 0 V'l z: V'l ....., ....., V'l 01-0 t.:' t.:' Q.. >-....., ..... ..... ..... z: z: .... V'l ..... ..... 03 ......... ....., V'l V'l z:....., <-' 0:: 0:: :::l :::l .... t.:' I-... ....... z: >-..... ..... ..... ..... z: 01-...... -..... ..... ......... u-0 u 0:: 0:: 0:: >-0:: 0:: 2: VI II-I-0 ....., I-...... 3 I-z: ..... ...... ...... ...... I ...... V'l ....., .... 0 0 ou.. 0 >-V'l 2: 0 V'l V'l ....., :I: :I: :I: I :I: I-0:: ..... IIII-I-....., ..... Q.. t.:' t.:' t.:' :I: t.:'UJ -I-z: z: z: t.:' z: 0:: 0 ....., ....., ........... ....., I-0:: :I: !-..... ..... ..... 0:: ..... V'l IITRAIL PLAN #1 14 7 ft. 11 mi. 1 mi. 2 mi. yes TRAIL PLAN #2 18 9.5 ft. 12 mi. 3 mi. 3 mi. no TRAIL PLAN #3 22 11.6 ft. 15 mi. 1.7mi. 5 mi. no FIG. 25 TRAIL COMPARISON MATRIX 65

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66 SUGGESTED TRAIL PLAN + 1 This plan is the least ambitious, from a total length perspective, of the three plans illustrated. The plan illustrates 14 total miles of trail linkages. This total averages out to approximately 0.0014 miles (7 feet) of trail per city resident. The trail system is categorized as follows: • 11 miles of the 14 miles total utilize existing or proposed drainageways. • 1 mile of the 14 miles total utilize street right-of-way. • 2 miles of the 14 miles total utilize lands that are independent of both drainageways and street right-of-ways. This plan would develop specific points along Coal Creek as trail junctions/activity nodes. Two of the three areas suggested for use as activity nodes are already under city responsibility (Coal Creek, south of Centaur Village and Coal Creek south of the Coal Creek Meadows Development). The trail system illustrated in Plan #1 is contained within the present City Limits of Lafayette, Since this system is contained within the city limits it is very likely that interactions with governmental agencies outside of Lafayette may be reduced as compared to the following two plans which extend beyond Lafayette City Limits.

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SUGGESTED TRAIL PLAN +2 This plan illustrates a trail system which has approximately 18 total miles of trail linkages. This system provides approximately 0.0018 miles (9,5 feet) of trail per resident. The trail system is categorized as follows: • 12 miles of the 18 miles total utilize existing or proposed drainageways. • 3 miles of the 18 miles total utilize street right-of-way. • 3 miles of the 18 miles total utilize lands that are independent of both drainageways and street right-of-way. This plan would develop specific reaches of the riparian zone along the north bank of Coal Creek into two relatively large strip parks. The parks can provide dual functions; the first function is that of a park environment with appropriate park activities, and the second function would be as a trail/connecting link which is routed through the park. 67

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SB SUGGESTED TRAIL PLAN +3 The third plan provides 22 total miles of linkages. This averages out to be 0.0022 Ul.6 feet) of trail linkage per resident. The trail system is categorized as follows: • 15 miles of the 22 miles total utilize existing or proposed drainageways. • 1.7 miles ot the 22 miles total utilize stTeet right-of-way. • 5 miles of the 22 miles total utilize lands that are independent of both drainageways and street right-of-way. This plan would develop the riparian zone along Coal Creek into a continuous strip park/connecting link. The majority of the 5 miles of suggested trail route that is independent of both drainageways or streets is that land which lies in the Coal Creek floodplain. Floodplains present constraints to commercial and residential development. Such a constraint makes developing the floodplain lands into a park an attractive and viable land use alternative,

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COMMON DESIGN ELEMENTS All three of the suggested trail plans have conceptual elements common, These shaTed elements are listed below: • Each suggested plan the existing and pToposed drainageways as the primary trail routing element, • Each plan provides connecting links to the primary points of interest in the city; i.e. residential, commeTcial, existing areas, parks, and schools. • Each plan utilizes the combination national/recreational trail concept. • Each plan provides for at least two trail connecting links to the City of Louisville (one along S. Boulder Road and one along Coal Creek). • Each plan provides for activity nodes at trail intersections. • Each plan m1n1m1zes use conflicts between motorized and non-motorized transportation modes. • Each plan allows for expansion of the system as development occurs and additional drainage data become available. • Each plan is compatible with the Colorado State Non-Motorized Trail Plan. • Each plan can accommodate linkages to adjacent communities. • Each plan is designed for phased implementation. • Each plan is designed to be compatible with city plans for parks development. The trail plans have been programmed to connect both existing and undeveloped park spaces in the city. 69

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70 EXAMPLE SITE DESIGN The segment of this section is an example site design, The site selected for this example is an exj,sting underdeveloped stomwater management facility in Lafayette, The design is intended to illustrate the concepts and programs developed in document, The site design is an example only and has not been adopted by the city, nor are there any plans pending at this time for its implementation. The particular site selected for this illustration is a functioning part of the stormwater management system in Lafayette. At the present time this site has the following characteristics. (see illustration 29 inventory) • A stormwater conveyance structure is routed through the site, • An underdeveloped maintenance road is routed adjacent to the stormwater runoff conveyance structure. • Three stormwater detention basins are located on the site. • The site is planted in "natural" grasses. • The site is not irrigated. • The site land area (approximately 6 acres) and site configuration make the development of a neighborhood strip park a viable design option. • One leg of the site j,s boardered by undeveloped land, This undeveloped land is currently undergoing a transition in land use from agricultural use to urban residential use. • The site is located in the midst of a single family, detached residential development.

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FIG. 29 SITE INVENTORY FCF--8 Alf?;A IN "Ntq"J\Ie;' rn ! j w -----'
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72 • An outlot is centrally located along the length of the site, • An dirt path has been routed through the existing outlot and across the • Existing recreational use is unprogrammed open space, Typical activities conducted on the site include; 1. bike riding generally by teens/young adults. 2. Free play 3. Informal trail connecting link between the residents of the development and located to the east. • A major public service electrial power distribution line is routed overhead through one leg of the site, The site offers the city and surrounding neighborhood several park and recreational opportunities. The selected design and activities (see illustration #30) are intended as an example of what could be done with this land area that is currently being used for managing stormwater runoff, All of the suggested recreation activities and facilities have been selected from the menu of multiple use alternatives inventoried in the Facility Inventory and Alternative Use Matrix (figure #24). The suggested trail illustrated on the site plan is routed adjacent to the stormwater conveyance structure. This trail is connected at each end of the site to conveyance structures which are routed throughout the development. These trail connections offer the opportunity to integrate the suggested trail with conveyance facilities entering and leaving the site. These connections will integrate the site with the city trail and park system.

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FIG. 30 AP.Pe.P 0 t.ertJ(J 1-IN.Pr: 17 WUFJ? Ull-I(Z1 A-? 1 .. ?uo Pi!-rtNW J:!:Nfl&-1 b? DRAINAGE FACILITY ADAPTED FOR MULTIPLE USE (J D B . -40

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74 Illustrations #31 and #32 are more specific examples of the designs suggested for the selected example site, The illustrations also demonstrate a few of the basic design utilized in implementing alternatives with stormwater management facilities. The illustrations also demonstrate how, with minor site grading modifications, detention basins can be designed for recreational uses while still serving the requirements of stoTmwater management. FIG. 31 CARlA DR. MUL n-uSE DESIGN

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P -'!ZI I"D!'FIG. 32 CARlA DR. MUL11-USE DESIGN SECTlON 75

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OUTLOT I ACCESS POl NT > -z 0 l3 w en

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GENERAL POLICIES & GUIDELINES This subsection of the case study proposes general guidelines for combining stormwater drainage and recreation facilities. The inventory includes both policy and physical design elements which will establish a system of combined uses for recreation and drainage facilities. The guidelines support the proposed multi-use concept described in an earlier section of this study and will facilitate the integration of future development drainage systems as well as provide a city-wide continuity of design theme. The guidelines which follow are intended to be used in conjunction with the trail plans and multiuse alternatives previously proposed to insure that the multiple use program can be implemented on a coordinated, city-wide scale. In keeping with the previous sections of this document the guidelines contained in this subsection are general in nature and in many instances present a range of design options. This format is necessary since a specific recreation oriented multi-use policy and consequent multiuse plan have not, as yet, been officially adopted by the city. Lacking a specific policy and plan, it would be inappropriate, at this time, to propose guidelines which are applicable to a particular use option. It would be, as an example, be less than efficient to provide a detailed inventory of guidelines for utilizing drainageway maintenance roads as bikeways if there is not a policy and consequent plan for this specific use. The intent of these guidelines is to provide a built environment that will permit the implementation of a recreation oriented multi-use, should such a policy be adopted in the future. • • • 76

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77 MULTIPLE USE POLICY A necessary first step in developing and implementing multiple uses for underdeveloped stormwater management facilites is to draft and adopt a clearly defined policy. Such a policy should clearly define the objectives of the residents of Lafayette. It is essential to have a well understood policy regarding multiple use before an effective plan can be formulated and adopted. Therefore, The city of Lafayette should draft and adopt a policy of multiple use for all stormwater management facilites. The policy should state that all drainageways and major drainage structures should be designed and implemented to respond to uses in addition to the single functions of collecting, storing, regulating, and conveying stormwater. Such uses can be active use areas such as trail, parks, recreation facilities, and etc. or passive function areas that are designed to be viewed as desirable visual elements in the cityscape. MULTIPLE USE PLAN The city of Lafayette should adopt a multiple use plan for its drainage facilities. Such a plan should respond to the multiple use policy as well as be compatable with the various existing plans and policies particular to Lafayette. The plan should reflect the hopes, goals, and aspirations of the residents of Lafayette, and respond to their percieved outdoor public space needs. The plan should also respond to the capabilities of the institutional support systems unique to Lafayette. The various plans and alternatives suggested in this document have all been formulated based on the above criteria. SUPPORTING CODES AND ORDINANCES A supporting system of codes and ordinances is necessary in order to insure that the implementation and use of the facilites follow the intent of the adopted policy and plan. The codes and ordinances should support in detail the adopted multi-use policy and plan. Such support legislation should specifically address the following issues:

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• The type and kind of multiple use for specific facility types • The construction criteria for the various multi-use facilities. • What user activities are appropriate for specific facilities. DEVELOPMENT DRAINAGE MASTER PLANNING In the interest of developing a multi-use stormwater management system which is efficient and effective the City of Lafayette should require that a master plan for managing stormwater runoff resulting from the proposed development be submitted as a part of the development package for review and approval. Such a master plan should include the existing, predevelopment drainage patterns drawn at the same scale as the required development final drainage plan. In instances where an entire site is not going to be developed at one time (the site will be developed in parcels), then it would be to the city's advantage to require a conceptual plan for those areas of the site to be developed at a later date. This system of master planning and drainage deliniation will allow for a wider scope of planning by the city. In all instances the drainage plans should be examined for the following: • The proposed drainage plans should be examined for their relationships to the drainageways proposed in the Phase B Development Plan. • How the proposed stormwater management facilities relate to the city-wide parks, recreation, and open space plans and facilites. • The relationships between the land required for managing runoff and the dedicated land required by the city. 78

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79 COORDINATING INTERDEVELOPMENT DRAINAGE FACILITIES The coordination of drainage facilities between adjacent developments and especially the interdevelopment coordination of drainageways and their collectors at the citywide scale is an important aspect of city-wide multi-use planning. The city should encourage the developer to coordinate the drainage system o his proposed development with the drainage systems and plans for all the other developments located in the same drainage basin. This coordination will promote a logical and programmed continuity to both the drainageways themselves and their requisite maintenance roads/multi-use trails. BARRIER FREE ACCESS AND' USE A concept that should be expressed throughout the various phases of planning and implementation of multi-use facilities is the concept of user access, mobility, and safety. This concept should ultimately result in sites and facilities which are free of barriers and hazards to those persons who find themselves either temporarily or permanently physically impaired. A parent pushing a stroller, a child pulling a wagon, a bicyclist, or a person requiring the use of a mechanical aid to compensate for a mobility impairment may find themselves unable to cope with a curb or a flight of stairs. In the interest of providing convenient access for all potential users to the environment it is proposed that all ordinances and codes regarding handicapped access be applied to the facilities suggested in this document. INTERIM AND POST CONSTRUCTION EROSION CONTROL Soil erosion during the project construction phase of development has resulted in excessive sediment deposits in stormwater management structures. Such sedimentation drastically reduces the ability of management structures to control stormwater runoff safely and efficiently-the structures are not functioning the way they were designed. In addition to inefficient runoff management, sedimentation can often result in land areas becoming

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mud flats or bogs which can be unsightly and limit the space's use potential. To insure an effective and efficient stormwater management system a sedimentation and erosion control plan should be an integral part of the development package presented to the City of Lafayette during the project review phase. The plan should focus on the methods and devices which will be utilized to control erosion and sedimentation during the interim and post construction phases of the development project. Periodic inspections of the site by the city during the project construction phase should include an inspection of interim sedimentation and erosion control measures and their effectiveness. Such periodic inspections and reviews will insure compliance with the original erosion control plans and determine whether additional measures are required to insure that sedimentation does not reduce the efficiency and effectiveness of stormwater management structures. A final inspection by the city should include the following items regarding erosion control. • All stormwater management structures are to be free of debris and sediment. If actions taken during the project construction phase have proved to be inadequate in this regard, then the developer should be responsible for taking whatever measures are necessary to insure the efficient operation of such structures. • Permanent measures have been taken to insure that debris and sedimentation which are likely to occur as a direct result of development do not reduce the effectiveness of runoff management structures in the future. The safe and efficient operation of stormwater management structures should be assured the residents of the development and the residents of the city prior to issuing a certificate(s) of occupancy. BC

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MINIMUM OUTLOT SIZE In the event outlets are to be used as access points to multi-use facilities the size and configuration of the outlot should be visually compatible with the developed lots in the immediate vicinity. In order to provide this compatibility the minimum outlot/access point lot frontage dimension should be no less than 60% of the average frontage dimension of the developed sites extending five lots on either side of the access point outlot. This size requirement will also provide enough land space for the installation of appropriate and adequate visual screening and physical barrier construction between the public space (outlot/access point) and adjacent private spaces (i.e. residential). The size requirement will also provide enough space for utilizing the type and kind of landscaping that will be at once a visual attribute to the community while being relatively easy to maintain. CITY-WIDE DESIGN CONTINUITY The City of Lafayette should continue to encourage and promote a continuity of design theme for multi-use facilities which projects an image of coordination and unity while allowing environmental variety. The design theme should be promoted at the city-wide scale to insure that the individual multi-use sites coordinate with each other to produce a unified, city-wide, system of multi-use facilities. The following measures can be exercised by the City of Lafayette to promote a continuity of design theme throughout the city without presenting an image of regimentation. • Develop and promote a uniform sign design for multi-use facilities which reflects the spirit and attitudes of Lafayette residents. Multi-use facility signage should have the following characteristics. All signs should be constructed of the same material. All signs should use the same lettering style.

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All signs should be the same texture. All signs should follow a prescribbed use of color All signs should be of uniform shape and configuration. A coordinated set of guidelines should be developed for sign location and placement. • Maintain a common design theme in site furnishings such as play equipment, benches, lighting fixtures, trash recepticles, and etc. • Insure that the landscaping coordinates with other site elements and uses. • Develop and promote a consistant use of paving materials based on anticipated use activity, site conditions, and maintenance requirements. • Insure that a common design theme is followed in the design of drainage structures such as headwalls, culverts, energy dissapaters, drop structures and etc. RESTRICTING UNAUTHORIZED VEHICLES The drainageway maintenance roads/rec. trails should be designed for periodic use by maintenance and emergency vehicles. However, the question of motor vehicle access and use of multi-use facilities, especially on the trails, by the general public is an issue that should be resolved prior to the physical design of the trails. Based on the interpretation of the documents researched for this case study the residents of Lafayette would likely prefer restricting the public use of the trails to non-motorized vehicles and pedestrians. General public use and access of motorized vehicles to and on the trail system should be discouraged. The following techniques can be used to discourage public use of motor vehicles on the maintenance roads/rec. trails. 82

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83 • Signs should be placed at all access points informing the public of city policy regarding appropriate trail use. Additional signs should be placed at strategic points along the maintenance roads/rec. trails which convey similar information. • The signs at access points should be located on the trail in such a way that they present a physical barrier to automobiles and the like. Such signs should be removable in order to allow access for emergency and maintenance vehicles. If necessary, the signs should be fitted with locks to which only authorized vehicles and users have the key (see figure #33). • Constrict the access point at the entry to 10 feet wide as shown in figure 33. This 101 width will allow for access of authorized vehicles once the sign is removed. The constriction also acts as a transition point which will further define the entry into a recreation zone. • Ordinances and codes should be adopted which support the intent of restricted use. MULTIPLE USE MAINTENANCE ROADS Figures 34, and 35 illustrate the conversion of the drainageway maintenance road into a multi-use recreation trail. As stated earlier, the drainageways proposed in the "Phase B Development Plan" include land area for maintenance road right of way . However, the "Phase B Plan" does not stipulate how the maintenance road is to be surfaced. If these maintenance roads are to be opened to the public for recreational uses (and once they were installed it would be very difficult to keep the public off of them), measures must be taken to minimize roadway deterioration. Without a protective surface treatment even infrequent use by authorized maintenance vehicles will result in severe roadway deterioration. To minimize roadway deterioration, drastically reduce maintenance and repair costs, and improve the overall appearance of the roadway, the roadways should be paved. As shown in figure

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85 35, the entire road width does not have to be paved. It is suggested that the maintenance roads only be paved to a width of 7 feet. This width is adequate for light maintenance vehicles (pickup trucks and etc.), is just above the minimum standard (6'-6") for a two lane bikeway, and is adequate for pedestrian use. Since the ' 'Phase B Development Plan" already proposes maintenance roads along the major drainageways, paving would be the only additional measure required to convert these maintenance roads into multi-use recreational trails. FIG. 34 fD' r.IIJ:'e.CI r-11 1-J. .. J.tU11!:1a F'b.vel:' 1W-

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SCREENING/PRIVACY CONTROL Screening measures should be taken in areas where public use lands (access lots, trails, and etc.) abut private property. This is particularly important in areas where recreation facilities run adjacent to private residences where residents must be assured of their privacy. The screening between public and private spaces should present both a visual and physical barrier to the public space user. An ideal situation would be to screen the views of the user of the public space while allowing the public space to be viewed by the adjacent private property resident (see figure 36). This is a particularly desirable condition because the public space can be monitored by persons having a interest in the adjacent public spaces. As illustrated in figure 36, this situation is readily adaptable to those sites used for runoff management since the lands adjacent to the drainageways and basins is generally graded to slope towards the particular drainage facility. l'P-IV.A-1"' _______ ......_ __ , Vlbi.A4\ e; l!\)'-t"'\e.-1'"" FIG. 36A SCREENING/PRIVACY CONTROL "( -t> \C.,!\\..-.... BS

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RG. 36 SCREENING/PRIVACY CONTROL 87

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STORMWATER DETENTION BASIN CONFIGURATION Stormwater detention basins offer opportunities for use as activity places. The range of activities which can be programmed into detention basin design are detailed in the facility inventory and alternative use matrix, figure 24. The uses range from open field free play areas to formal areas for sitting and relaxing in a park-like atmosphere. In order to enhance the multi-use opportunities for these detention facilities it would be beneficial to adjust the configuration of the typical detention facility. At the present time the detention facilities being installed in the developments in Lafayette are generally very ridged and structured. The general configuration is typically too geometric with the predominant shapes being squares and rectangles. The following principles, if implemented, will greatly enhance the range of multi-use options that can be implemented in these currently underutilized spaces. The basin rim shape should be modified to provide a more organic/curvilinier form. A detention basin with a more curvilinier rim shape is generally more visually appealing than a detention basin that has a more formal and ridgid geometric form. The depth of the detention facility should be kept to a minimum. This minimum depth will allow for activities to be conducted in the basin without the user feeling as though he or she is in a hole. The slopes of the basin sides should also be kept to a minimum. Shallow slopes on the sides of the basins will allow for easier user access and enhance the feeling of open space for the user. The principles detailed above are general in nature and as such are not quantified. It would be difficult, and in many applications inappropriate, to quantify design criteria for detention basins given the varying site conditions under which detention basins are implemented. A major consideration in detention basin design is the capacity of the basin. The basin must be able to store, and regulate the release of stormwater as prescribed BB

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in the Lafayette Stormwater Facility Design Criteria. It should be noted that if the general principles described above are implemented, the detention basins are likely to require more land area than they would if they were designed strictly for stormwater management alone. For this reason detention basin design should be evaluated on a case to case basis. Such a case to case evaluation offers the city the option of combining dedicated open space with stormwater management facilities. An added benefit of case to case evaluation is that it can provide the city and the developer with foundation guidelines for the desirable location of dedicated open space. The ideal situation would be for the city to have a programmed recreational use for the areas required for stormwater detention based on the location of the facility and the recreational need of the surrounding community . Such preprogramming will enable the city and the developer to negotiate toward the common goal of quality recreational spaces for both the resldents of the proposed development and the residents of the entire community of Lafayette. Figures 37 and 38 illustrate the basic principles of reducing the depth of detention facilities as well as reducing the basin side slopes. .fil W Plrf 1&-L.iL;:I 0 FIG. 37 -BB

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FIG. 38 + IN A!'-M . D HUI.-11"' I , ""'IJ1"e. t.Ht-NNet.... NL.JL.-11• MULTI-USE FACILITY ACCESS An aspect of multi-use facilities that must be addressed in the early stages of development design is facility accessibility. In order to derive the maximum amount of benefit from a trail system convenient access must be provided the user. Without convenient access it is unlikely that the trail system will provide maximum benefit to the community. In order to insure convenient trail and recreation facility access at least one clearly marked outlot should be provided for each block of the development that abuts or adjoins a multi-use facility. The location of the outlot should be determined by; 1. the drainage/ runoff management requirements, and 2. the free and easy access to the multi-use facility by as many potential users as possible. Figure 38 is an illustration o f this design principle. 90

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RG. 38 FACUlY ACCESS/OUTLOT LOCA110N

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SURFACING MATERIALS Ground surface treatment is an important element in the design of facilities. As already mentioned in this document, measures should be taken to reduce the deterioration of trails and other facilities. Areas of anticipated intense use such as trails and the like should have a surface treatment which responds to tne following determinants. • Minimize the environmental degradation of the trail and the immediate area surrounding the trail. • Minimize long term maintenance and repair costs for the trail. • Provide visual definition and continuity to the trail system. The major factors to be considered in selecting a surfacing material are initial installation expense and long range maintenance and repair costs of both the surface installed and the surrounding trail area. Figure 39 illustrates the various surfacing materials which are acceptable for high use areas. The materials are illustrated accompanied by their commensurate design considerations. As noted in the illustration, premanent type paving materials (asphalt and concrete) have a relatively high installation cost. Site conditions being equal, concrete paving generally offers the most permanent surface with the lowest maintenance costs. However, the installation costs for concrete surfaces are usually substantially higher than the installation costs for alternative materials. In the interest of long range costs and particularly the maintenance and repair aspects of surfacing material, an all weather, permanent type of surfacing material most adequately serves the criteria for trails. The selection of a permanent surface material generally comes down to a choice between bituminous (asphaltic) materials or concrete. Bituminous materials generally offer a substantial cost saving for initial installation, but 92

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93 bituminous materials generally require periodic resurfacing whereas concrete does not. Figure 40 illustrates the various asphalt trail paving installations compatable with the various soil conditions likely to be encountered in Lafayette. Since the trails are likely to be installed in or around areas of possible inundation by stormwater the installation required for poorlydrained soils offers the best opportunities for permanence and low maintenance. An added safeguard for 'installation is to specify that the paving be laid on an undisturbed subbase or a subbase which has been compacted to 95% of the undisturbed soil density. 1\!IIII!\UIII!I Cone. J ::..1 Concrete ... :'1 Stone Chips J MSfj Soi 1 Cement Earth Wli!Wiwooo "'"""' J All weather, permanent surfaces : (most widely used; highest installation costs, longest wearing life; especially good for heavy use in urbanareas . ) Wood Surfaces : (use only when laid perdendicular to direction of travel, usually on light bridges, boardwalks, etc.) Source: "Barrier Free Site Design." U.S. Dept. of Housing & Urban Development. Washington, D .C.: GPO, 1977. FIG. 39 SURFACING ALTERNATIVES

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STANDARD CONSTRUCTION e>tf; lANDS a GRAVELl liLTS a CLAYS POORLY DRAINED FIG. 40 SOIL TYPES & PAVING ALTERNATIVES 94

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TRAIL RADIUSES, AND MINIMUM CLEARANCES Since the trails routed adjacent to the main drainageways of Lafayette are to be used as drainageway maintenance roads as well as recreational trail linkages the trail right of way and access points should be kept clear of obstacles to vehicular movement. Figures 41 and 42 illustrate the design principle of desinging the surfaced portion of the trail curves to respond to a particular recreational user group (pedestrian, bicycles, etc.) while responding to infrequent maintenance and emergency vehicle use. The primary principle illustrated in figure 42 is that the lands adjacent to the surfaced portion of the trail (the trail right of way) should be kept free of obstructions to vehicles. This principle is applicable to all segments of the trail, but is particularly relevant to those curved portions of the trail. The minimum area that should be clear of obstacles should be that land area inside an arc described by a 48 foot radius line. A 48 foot radius line is an accepted standard ("Architectural Graphic Standards) for the minimum turning radius of the typical fire truck. Other vehicles such as maintenance vehicles ( light trucks, tractors, mowers, and etc.) as well as emergency vehicles (ambulances, police cars, code enforcement, and etc.) are anticipated to be smaller than the typical fire truck and therefore require a turning radius area less than 48 feet. Figure 41 illustrates the design principle of maintaining a minimum overhead clearance of 10'-00". Minimum trail curve radiuses should be determined based on the trail user group and access for maintenance and emergency vehicles. If the primary user group is to be pedestrians then the radiuses should be designed relatively short in order to provide curves of tight turning radiuses. Tight turning radiuses will curtail bicycle speed and thereby aleviate pedestrian/bicyclist user conflicts. A formula has been proposed for establishing bicycle speeds and is documented in the U.S. Dept. of Housing & Urban Development's publication, "Barrier Free Site Design." The formula is shown below. R=l. 2SV + 1. 4 Where R is the unbreaked radius of curvature (in feet) negotiated by a bicycle on a flat, dry, bituminous concrete surface. V is the velocity of the bicycle in mph. 95

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96 The recommended design speed for bicycles on urban bike paths is 10 mph. It is recommended that if _the trail is to be designed primarily for pedestrian use then a maximum bicycle speed should be regulated to 5 mph. Figure 43 illustrates additional design criteria for bikeways should bicyclists be chosen as the primary trail user group. As figure 43 illustrates, design criteria for bikeways varies from source to source. A general rule of thumb is listed in the "Handbook of Landscape Architectural Construction" as follows. '' ... on the whole, routes should not exceed 7% grade. Grades 100 feet long or less can be up to 15% though this is not desirable. Subtract 1% for each additional 50 feet of slope length; therefore a 400 root grade should not be over 11%. Grades over 1,000 feet long should be kept at 5% or less, if at all feasible." An added note regarding slope, if the guidelines for barrier free site design and handicapped use are followed then the slope requirements covering bikeways will be satisfied. A final point that should be addressed in the design of bikeways is the addition of curb ramps for easy access from the street to the trail. Figure 44 illustrates the minimum design standards for access ramps.

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WIDe:-fA.......et' J Of-....... -lb. \NlDE:. W./ ... FIG. 41 OVERHEAD TRAIL CLEARANCE ..... "--------------97

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--. tr our 1"t' -rt' ... 1"UIZNII--I6! fZ.a'H ........ FIG. 42 TRAIL RIGHT OF WAY CLEARANCE !38

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DESIGN CONSIDERATIONS Horizontal bikeway clearance Vertical bikeway clearance Speed Bikeway width for two-way traffic Grade in percent Curve radius Bikeway capacity GUIDELINES 10 ft. (max. desirable) ft. (min. desirable) 8 ft. 10 mph 5 ft. 3 in. min. 8 ft. recommended Max. for short runs (up to 100ft.) 15% Recommended short run max.; 10% Desirable max.; 5 % Min. 8 ft. Comfortable min. 15 ft. Average recommended 20 ft. 4 ft. wide = 1,000 bikes/hour/ one way Excerpt of table presented in "Handbook of Landscape ArchiteCtural Construction." Jot D. Carpenter, ed. Mclean, Virginia; Landscape Architecture Foundation, Inc. 1976. BIKEWAY GRADIENT 1. 7 % 2.0 % 2.5 % 2.9 3.5 4.0 4.5 Df:SIRABL.E LENGTH OF GRADE 590 410 262 200 148 102 82 Source: "Bikeway Planning Criteria and Guidelines Institute of Transportation and Traffic Engineering. " U. of California at Los Angles. April 1972. FIG. 43 ADDITIONAL BIKEWAY DESIGN CRITERIA 99

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FIG. 44 CURB RAMPS t1Il A'/PIP"l.--1 P '' &! UiJ t---tt:::::e=f6 ... e.e \'-' "-l" HINIHUH f"oP-ID ? w'fh FIG. 45 BICYCLE TURNING RADIUSES

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GEtRAL. REFERENCES 1. Carpenter, Jot D. ed. Handbook of Landscape Architectural Construction. Mclean, Virginia: Landscape Architecture Foundation, 1976. 2. DeChiara, Joseph, & Lee E. Koppelman. Site Planning Standards. New York: McGraw-Hi.ll, 1978. 3. DeChiara, Joseph, & Lee E. Koppelman. Urban Planning and Design Criteria. New York: Van Nostrand Reinhold, 1982. 4. Gold, Seymour M. Recreation Planning and Design. New York: McGraw-Hill, 1980. 5. Ramsey/Sleeper. Architectural Graphic Standards. 7th ed. New York: John Wiley & . Sons, 1981. 6. Sheaffer, John R., Kenneth R. Wright, with William C. Taggart, & Ruth M. Wright. Urban Storm Drainage Management. New York: Marcel Dekker, Inc., 1982. 7. U.S. Dept. of Interior, Bureau of Outdoor Recreation. Guidelines for Understanding & Determining Optimum Recreation Carrying Capacity. Washington, D.C.: GPO, Jan., 1977. 8. Wright-Mclaughlin Engineers. Denver Regional Council of Governments Urban Storm Drainage Criteria Manual. 2 vols. Denver: Urban Drainage & Flood Control Dist., March, 1969. SITE SPECIRC REFERENCES 1. Boulder County Comprehensive Plan. As amended June, 1980. Boulder County, Colorado. 2. Boulder County Public Works Dept. City of Lafayette Transportation Plan. Sept., 1980. 3. Camp, Dresser & McKee Inc. Basinwide Drainageway Planning City of Lafayette and Surrounding Boulder County, Colorado Phase A Development of Alternatives. Urban Drainage & Flood Control District, City of Lafayette, Boulder County, March, 1980. 4. Camp, dresser, & Mckee Inc. Major Basinwide Planning City of Lafayette/Boulder County Phase B Development of Preliminary Plan. Dec., 1980. ,.. >< -c z w a. a. <

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5 . City of Lafayette and Surrounding Unincorporated Areas of Boulder County, Colorado Storm Drainage Design and Technical Criteria. Aug. , 1980. 6. City of Lafayette and Surrounding Unincorporated Area of Boulder County, Colorado Storm Drainage Design & Technical Criteria Amendment No. 1, May, 1982. 7. City of Lafayette Planning Dept. Land Use Plan. Aug., 1981. 8. City of Lafayette Parks, Recreation, and Open Space Plan. 1981. 9. E.D.A. W . Colorado State Recreational Trails Program, Non-Motorized Plan . Colorado Division of Parks & Outdoor Recreation , 1981. 10. Schlupp-Ferguson Associates . The Lafayette Comprehensive Plan 1973. Lafayette, CO: Sept., 1973. 11. U.S. Dept. of Agriculture, Soil Conservation Service. Soil Survey of Boulder County Area, Colorado. Washington, D.C.: GPO, Jan., 1975 12. Micheal Acimovic, City of Lafayette Administrator 13. Kathy Davis, City of Lafayette Planning Director 14. Tom Hoby, City of Lafayette Parks, Recreation, & Open Space Director 15. Warren Williams, City of Lafayette Public Works Director

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MAP No. 1. MINE SUBSIDENCE HAZARD AREAS 2. HYDROGRAPHY 3. TOPOGRAPHY 4. GENERAL SLOPE CONFIGURATION 5. CONSTRAINTS TO LOCAL STREETS AND ROAD CONSTRUCTION 6. CONSTRAINTS TO PICNIC AREA CONSTRUCTION 7. CONSTRAINTS TO PLAYGROUND CONSTRUCTION 8. CONSTRAINTS TO THE CONSTRUCTION OF BUILDINGS WITHOUT BASEMENTS 9. CONSTRAINTS TO SHALLOW EXCAVATIONS 10. NON-IRRIGATED CROP CLASSIFICATION 11. IRRIGATED CROP CLASSIFICATION 12. WOODLAND SOILS CLASSIFICATION 13. SEWAGE LAGOONS 14. CONSTRAINTS ON SEPTIC TANK USE The maps included in this appendix are taken from; The Lafayette Comprehensive Plan, 1973 prepared by Schlupp-Ferguson -L.G.A. Associates, 1973. The maps are included as a ready reference only. For additional information on soil classification, and construction constraints catagories see: 1) Soil Surve of Boulder Count Area, Colorado. U.S. Dept. of Agriculture, and 2 The Lafayette Comprehensive Plan. M X .... c z w <

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'104 PROJECTED IE DRIFT ENTRY MAP MINE SUBSIDENCE HAZARD AI

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r.J SUB-BASIN [) DRAINAGE lSI STREAM AREA 1':1 FLOOD PLAIN L.:!LLIMITS MAP#2 HYDROGRAPHY

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'106 MAP TOPOGR

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0 0-2% 0 2-15% • 15%+ lSl CITY LIMIT MAP #t. SLOPE CONFIGURAllOI

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D SEVERE El) MODERATE D SLIGHT MAP STREET & ROAD CONSTRUCllON

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0 SEVERE 0 MODERATE 0 SLIGHT MAP#6 CONSTRAINTS TO PICNIC AREA

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0 SEVERE 0MODERATE 0 SLIGHT 0 MAP PLAYGROUND A

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0 SEVERE !1J3 MODERATE 0 SLIGHT The Pfeoat&tion ol tf'lll I1Mnelally .. dreG thiOUOfl a or.,u trom thrl o.o.n"*'' Housu'O and Urba n o..tiopn'4nt unoet !he Urban Pi & MII'IQ anca PrOQram authorihd ' " tiM, uii'I'WftOed. MAP#8 CONSTRAINTS TO BUILDINGS WITHOUT BASEMENT!

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D SEVERE G'J MODERATE 0 SLIGHT CONSTRAINTS TO SHALLOW EXCAVA11

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8 ... (]viE, VII E 01v E Qme 0 UNCLASSED The ol!hlt r.oort w• hi\MC.Ially aJOtd lht0u9fl • F _,.,. ;ram from tne Oeoiwtment ot Hou t •ng ano um.en O....oom.nt under tne uroan i='lann•no Au•alance Pfo9tatn authOflteG '" \ NON-IRRIGATED CROP CLASSIFICA TIO

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• m E , D••E. liS 0 •

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OLLV:>l:IISSYD S110S ON\f'IOOOM :t..-# c:IVW t 1 dno11oQ • • dnowo 0 I dnOIIO fiil e • dnOIID II

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0 MOST SUITED MAP SEWAGE LAG

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0 SEVERE B MODERATE 0 SLIGHT MAP#1

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city of PI ann i ng Department 665-9271 TO: John Goebel FROM: Lafayette DATE: February 15, 1983 SUBJ: STORM DRAINAGE MULTI-USE PROJECT Multiple Use of Drainage and Detention Areas Parks and Recreation Department Objectives 1. To determine Which areas owned by the City for the purpose of storm drainage are useable as Parks, Recreation Areas or Open Space. 2. After identifying the various sites which may have some multiple use potential the type of use and development required should be determined. 3. When determining uses and development the following should be considered -Cost to maintain and operate the site -Desires of nearby home and property owners -How uses relate to the natural and man made environments -How uses and development relate to the City of Lafayette's plans and goals for Parks and Recreation and Open Space -Cost to develop such sites 4. Possible development of a "spectrum" which might identify uses and how they relate to #2 and #3, i.e. natural areas, trails, bikeways, fitness stations, playgrounds, etc. 5. To incorporate specific recommendations based on the above for the potential areas now being used soley for storm drainage 6. To incorporate bikeways and/or pedestrian trails in these areas to provide alternative access routes to city parks and recreation facilities, shopping areas and other places of interest

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John Goebel Storm Drainage Multi-Use Project 2/15/83 Page 2 7. Review other multiple use alternatives --whatever they might be? 8. Future development of storm drainage areas --criteria for requiring developers to place these facilities at a certain location on the site 9. Minimum and maximum sizes of storm drainage areas for effective use. 5 acre? 1 acre? 4A 55802 9