EPA/625/R-93/004
September 1993
Handbook
Urban Runoff Pollution
Prevention and Control Planning
U.i Environmental Protection Agency
Cent
i'ce of Research and Development
/for Environmental Research Information
Cincinnati, Ohio
Printed on Recycled Paper
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Notice
This document has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and
administrative review policies and approved for publication. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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Contents
Chapter 1 Introduction. 1
Purpose of Handbook ..... 1
Target Audience of the Handbook 2
Overview of Urban Runoff Pollution 2
References 8
Chapter 2 Regulatory Framework 9
Storm Water NPDES Permit Program 9
Combined Sewer Overflow Strategy 10
Pollution Prevention Act (. 11
Safe Drinking Water Act 11
Nonpoint Source Management Program 12
Coastal Zone Nonpoint Source Pollution Control 12
Clean Lakes Program 13
National Estuary Program 14
Agricultural Nonpoint Source Programs 14
Summary , 15
References 15
Chapter 3 The Planning Process 17
Description of the Planning Process 17
Initiate Program 20
Determine Existing Conditions 21
Collect and Analyze Additional Data 22
; Assess and Rank Problems 22
Screen Best Management Practices 22
Select Best Management Practices. 23
Implement Plan 23
Summary 23
Case Study: City of Lewiston, Maine, CSO, Storm Water, and Nonpoint Source
Planning Program 24
References 28
iii
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Contents (continued)
Page
Chapter 4 Determine Existing Conditions . 29
Preparing a Watershed Description 29
Preparing a Receiving-Water Description 35
Summary 39
Case Study: Cily of Lewiston, Maine, CSO, Storm Water, and NPS Planning
Program Existing Conditions Assessment 40
Case Study: Pipers Creek Watershed Characterization and Water Quality
Assessment 47
References 51
Chapter 5 Collect and Analyze Additional Data 53
Objectives of Data Collection 53
Data Collection Programs '. 54
Cost Estimating for Data Collection Programs 63
Data Management and Analysis , 64
References 73
Chapter 6 Assess and Rank Problems 75
Problem Assessment Criteria 75
Resource Assessments 84
Institutional Assessments 88
Goals and Objectives Assessments 88
Problem Ranking 88
Case Study: Ohio Environmental Protection Agency Biological Criteria for the
Protection of Aquatic Life 92
References 97
Chapter 7 Screen Best Management Practices 101
Best Management Practice Overview 101
Best Management Practice Screening 102
Best Management Practice Descriptions 107
Case Study: City of Austin, Texas, Local Watersheds Ordinances 130
References 134
IV
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Contents (continued)
Page
Chapter 8 Select Best Management Practices 137
Alternatives Development 137
BMP Selection Process 140
Conclusions 147
Case Study: Maine Department of Environmental Protection
BMP Selection Matrix 148
Case Study: Santa Clara Valley, California, Nonpoint Source Control Program
BMP Screening Procedure 151
References 156
Chapter 9 Implement Plan. .... 157
Contents of an Urban Runoff Pollution Prevention and Control Plan 157
Summary 164
Case Study: Pipers Creek Watershed Action Plan for the Control of Nonpoint
Source Pollution 165
References 168
Appendix A Additional References 169
Hydrology References 169
Water Resource Sampling References... 169
Other Nonpoint Source Pollution References 169
Appendix B Table of Annotated References 171
Appendix C Acronyms and Abbreviations 173
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List of Figures
Figure
Page
1-1 "typical changes in runoff flow resulting from paved surfaces 4
1-2 Pre- and postdevelopment hydraulics 4
3-1 Urban runoff pollution prevention and control planning process 19
3-2 Watersheds in Lewiston, Maine 25
4-1 Total suspended solids (TSS) concentrations 39
4-2 Pipers Creek watershed 48
5-1 Example stage discharge rating curve. 63
5-2 Fecal coliform densities at Station A . 66
5-3 Fecal coliform densities at Station E 66
5-4 Relationship between flow and pollutant concentrations 69
5-5 Untransformed total suspended solids (TSS) data 70
5-6 Log-transformed total suspended solids (TSS) data 70
5-7 Distribution of macroinvertebrate indicator species along a sewage leachate-affected stream..... 72
5-8 Cluster analysis dendrogram for sewage-affected stream survey results 73
6-1 Schematic representation of watershed...'. 90
6-2 Number of species vs. drainage area for determining 5, 3, and 1 index of biotic
integrity (IBI) scoring 94
6-3 Total taxa vs. drainage area for determining 6, 4, 2, and 0 invertebrate community
index (IC1) scoring 96
7-1 Sample nonstructural control screening matrix 104
7-2 Extended detention pond 112
7-3 Wet detention system 114
7-4 Example shallow-constructed wetland system design for storm water treatment 115
7-5 Example wet detention system design for storm water treatment 115
7-6 Sample infiltration basin 117
7-7 Sample infiltration trench 118
7-8 Porous pavement cross section 119
7-9 Sample grass-lined swale 120
7-10 Schematic design of a filter strip 121
7-11 Conceptual design of a filtration basin 122
7-12 Schematic design of sand filter 123
7-13 Conceptual water quality inlet 125
7-14 Total suspended solids loading vs. percent impervious cover 133
8-1 Example alternative development process 139
8-2 Phosphorus removal for candidate control programs 140
8-3 Conceptual diagram of BMP selection method 141
8-4 Example continuous simulation results 142
8-5 Example cost-benefit ratio curve 144
8-6 Santa Clara Valley watershed 152
8-7 BMP selection process 154
9-1 Example CSO control conceptual design of a sedimentation/disinfection facility 158
9-2 Example runoff control conceptual design for a filter system 158
9-3 Sample agency responsibility matrix 161
VI
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List of Tables
Table
1-1
1-2
1-3
2-1
3-1
3-2
3-3
3-4
3-5
3-6
4-1
4-2
4-3
4-4
4-5
4-6
4-7
4-8
4-9
4-10
4-11
4-12
4-13
4-14
4-15
4-16
4-17
4-18
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
6-1
6-2
6-3
6-4
6-5
6-6
Page
Comparison of Water Quality Planning Projects
Summary of Urban Runoff Pollutants ... *
Relative Contribution of Nonpoint Source Loading .... .........
Estuaries in the National Estuary Program as of 1993.
Planning Approaches Defined in Regulatory Programs
Planning Approaches Defined in the Literature „
Federal and State Regulation of Urban Runoff
Land Use Near Major Watersheds in Lewiston, Maine
City of Lewiston Initial Water Resources Goals
Comparison of Maine Water Quality Standards
Use of Mapping Resources for Urban Runoff Planning .•.
Land Use and Land Cover Classification System. ,
Federal Sources of Watershed-Related Data
Federal Sources of Geographic Information System Mapping Data
Use of Nonstructural Practices in Study Area Watersheds
Frequency and Types of Nonstructural Practices Used in Study Area Watersheds
Existing Regulatory Control Summary—Subdivision Control
Federal Sources of Water Resource and Hydrology Data
Example Water Resource Data Spreadsheet
Lewiston Watershed Data
Summary of Lewiston Nonstructural Controls—Conservation Districts
Summary of Lewiston Nonstructural Controls—Performance Standards
Summary of Lewiston Nonstructural Controls—Development Review Standards
Existing Source Controls/Municipal BMPs
Lewiston Existing Structural Controls
Lewiston Source Input and Receiving-Water Data
Pipers Creek Watershed Characterization Data
Pipers Creek Water Quality Characterization Data
Priority Pollutants in at Least 10 Percent of Nationwide Urban Runoff Program Samples,
Storm Water Sampling Parameters ,
.Detection Frequencies of the Most Frequently Occurring Organic Compounds ...-.,
Typical Combined Work/Quality Assurance Project Plan
Example Spreadsheet Format for Water Resource Data
Spreadsheet to Calculate Nitrogen Loads
Commonly Used Statistical Calculations
CSO Sampling Results for Total Suspended Solids
Commonly Used Ecological Diversity Indices
Diversity Indices for Sewage Leachate-Affected Stream Samples ,..,..
Criteria for the Assessment of Pollution Problems
Types of Activities and Associated Pollutants
Water Quality Characteristics of Urban Runoff for the NURP Site
Characteristics of Rainfall, Storm Water, Combined Wastewater, and Treated Effluent ..
Estimated Urban Runoff Loadings Using Constant Concentrations
Comparison of Urban Runoff Models
. 3
. 5
. 6
14
17
18
25
26
26
27
30
31
32
33
34
35
36
37
38
41
42
43
44
45
46
46
49
50
55
55
55
58
65
65
67
68
71
72
76
77
79
80
80
83
vii
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List of Tables (continued)
6-7 Comparison of Receiving-Water Models 87
6-8 Characteristics of the Targeted Areas and Estimated Concentration Loads 91
6-9 Estimated Total Suspended Solids Loads for Targeted Areas 91
6-10 Prioritization Analysis for Urban Area Targeting 91
6-11 Index of Biotic Integrity (IBI) Metrics 93
6-12 Qualitative Assessment of Index of Biotic Integrity (IBI) Values 94
6-13 Qualitative Assessment of Modified Index of Well Being (Mlwb) Values 95
6-14 Qualitative Assessment of Invertebrate Community Index (ICI) Values 96
6-15 Indices of Biotic Integrity for Two Headwater Stations in Hocking River, Ohio 97
7-1 Urban Runoff Pollution Control BMPs 102
7-2 Structural BMP Initial Screening Criteria 106
7-3 Maximum Development Intensity 131
7-4 Barton Creek Development Requirements 134
8-1 Sample BMP Selection 138
8-2 Example Matrix Comparison 145
8-3 Example CSO Abatement Alternative Matrix Comparison 146
8-4 Priority Estuary Storm Water Control Matrix 149
8-5 Nonpriority Estuary Storm Water Control Matrix 150
8-6 Summary of BMP Treatment Level Codes 150
9-1 Potential Implementation Responsibilities 162
9-2 Pipers Creek Action Plan Recommendations 167
VIII
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Acknowledgments
This handbook is the product of the efforts of many individuals. Gratitude goes to each person
involved in the preparation and review of the document.
Authors
David Bingham, William Boucher, and Peter Boucher of Metcalf & Eddy, Inc., Wakefield, MA, were
the principal authors of this handbook.
Technical Contributors
The following individuals provided invaluable technical assistance during the development of this
handbook:
Thomas Mumley, San Francisco Bay Regional Water Quality Control Board, Oakland, CA
Austan Liebrach, City of Austin, Environmental and Conservation Services Department,
Austin, TX
Richard Field, U.S. EPA, Office of Research and Development, Storm and Combined
Sewer Program, Edison, NJ
Michael Brown, Doctoral Candidate, Cranfield Institute of Technology, School of Water
Sciences, Woldingham, Surrey, UK
William Swietlik, U.S. EPA, Office of Water, Storm Water Section, Washington, DC
William Tate, U.S. EPA, Office of Water, Storm Water Section, Washington, DC
• Richard Gustav, City of Seattle, Engineering Department, Drainage and Wastewater
Utility, Seattle, WA
Christopher Branch, City of Lewiston, Department of Public Works, Lewiston, ME
Steven Johnson, City of Lewiston, Department of Public Works, Lewiston, ME
Joyce Noel, Maine Department of Environmental Protection, Augusta, ME
Peer Reviewers
The following individuals peer reviewed this handbook:
Thomas Davenport, U.S. EPA, Region V, Watershed Management Unit, Chicago, IL
Eric Livingston, Florida Department of Environmental Regulation, Stormwater
Management Section, Tallahassee, FL
Earl Shaver, Delaware Department of Natural Resources and Environmental Control,
Division of Soil and Water Conservation, Dover, DE
Editorial Reviewers and Document Production
Heidi Schultz, Eastern Research Group, Inc. (ERG), Lexington, MA, provided editorial review and
produced this handbook.
ix
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Technical Direction and Coordination
Daniel Murray, U.S. EPA, Office of Research and Development, Center for Environmental
Research Information, Cincinnati, OH, coordinated the preparation of this handbook and
provided technical direction throughout its development.
Special Thanks
Lawrence Martin, U.S. EPA, Office of Research and Development, Office of Science, Planning
and Regulatory Evaluation, Washington, DC, provided support and assistance during the
preparation of this handbook. His efforts were truly appreciated.
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Chapter 1
Introduction
Purpose of Handbook
Urban runoff pollution sources, including storm water,
combined sewer overflows, and diffuse or nonpoint
sources of water pollution, are formidable obstacles to
achieving water resource goals in many municipalities.
Because these types of pollution sources are best
addressed locally, the U.S. Environmental Protection
Agency (EPA) has prepared this handbook to provide
local officials with a practical planning approach for
developing and implementing urban runoff pollution
prevention and control plans in urban settings.
This handbook is designed to serve as an overall
reference. Other references and guidance manuals
have addressed specific aspects of storm water and
urban nonpoint source (NPS) control, such as best
management practice (BMP) design (Schueler, 1987;
Tourbier and Westmacott, 1981), monitoring (U.S. EPA,
1988), and regulatory compliance (U.S. EPA, 1991,
1992a,b,c). This handbook, however, presents a
step-by-step planning approach that municipal officials
can use to develop technically feasible, targeted,
affordable, and comprehensive urban runoff pollution
prevention and control plans. Based on information from
numerous references, this handbook is both an
information source for urban runoff pollution issues and
a guide to the planning and implementation of effective
pollution prevention measures and controls. It will also
help municipalities comply with evolving environmental
regulations related to urban runoff management and
control.
The handbook is divided into chapters that outline a
step-by-step planning process. The planning process
emphasizes and addresses the following considerations:
• A multitude of diffuse pollution sources exist (e.g.,
combined sewer overflows (CSOs), storm water, and
NPS), and each type of source often has specific
regulatory requirements. The planning approach is
designed to be flexible enough to address these
numerous sources (including point sources) and
regulations or to focus on specific sources or
regulations.
o While a high level of complexity and uncertainty is
unavoidable in urban runoff control planning, this
handbook is designed to minimize such difficulties by
identifying a clear series of logical steps for the
analysis. These steps are founded on what various
regulations require, what is described in the technical
literature, and what is standard practice for planning.
Each chapter in the handbook describes one of these
steps.
• Municipalities need a flexible approach based on the
problems to be solved and available resources. The
handbook, therefore, presents a-range of options
(from simple to complex) for the major steps in the
planning process. Examples of these options are
provided and case study descriptions are included to
demonstrate their use.
« Numerous published resources address particular
aspects of or steps in the planning process. Rather
than repeat this literature, this handbook refers to the
best sources and shows where and how to apply
them in the planning process.
« It is more cost effective to prevent potential
urban runoff pollution problems and protect
existing resources than to implement pollution
controls once a problem exists. Therefore, this
handbook emphasizes pollution prevention and the
implementation of regulatory controls designed to
protect existing resources.
This chapter provides an overview of urban runoff
pollution issues including types of pollutants, their
origins and modes of transport, and their effects on
receiving waters. Chapter 2 discusses the regulatory
framework and the agencies and programs that deal
with urban runoff pollution prevention and control.
Chapter 3 describes the planning process set forth in
this document. It stresses the iterative nature of storm
water and urban NPS pollution prevention and control
planning, and the need to set goals that can be
reassessed and refined as efforts progress.
Subsequent chapters discuss each step in the planning
process for the development of an urban runoff pollution
prevention and control plan. The process includes
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assessment of existing conditions using available data
(Chapter 4), collection and analysis of supplemental
data (Chapter 5), problem assessment and ranking
(Chapter 6), screening (Chapter 7) and selection
(Chapter 8) of pollution prevention and control
strategies, and definition of the selected plan (Chapter 9).
Target Audience of the Handbook
This handbook has been prepared for municipalities
seeking to comply with evolving Urban runoff regulatory
requirements and to improve or protect water resources
and their uses through efficient and cost-effective
pollution prevention and control strategies. The
information in this handbook is primarily oriented to
urban and suburban communities with residential,
commercial, and industrial areas. Rural communities
with extensive agricultural areas are not directly
addressed, although some techniques discussed in the
handbook are applicable. This document can also be
used by state agencies, local environmental groups,
and other entities responsible for or interested in
protecting water resources. The handbook can be a
resource to persons of diverse backgrounds
implementing an urban runoff pollution prevention and
control project. For example, it can be used by a
muItMsciplinary team (from city or county governments)
that might include engineers, biologists, planners,
chemists, political officials, environmental group
members, and residents, all contributing their expertise
and resources to the project.
Overview of Urban Runoff Pollution
Urban runoff pollution results from numerous sources.
It is the result of rainfall and snow melt that becomes
contaminated as it travels through the atmosphere,
along the land surface, and makes its way to a water
body. Urban runoff can enter a water body from an
identifiable point source, such as a separate storm
sewer outfall or a combined sewer overflow. It can also
flow directly into a water body without an easily
identified point of entry. Regardless of the point of entry,
urban runoff has diffuse origins and, therefore, is difficult
to manage and control.
EPA regulates certain point source discharges of urban
runoff through the National Pollutant Discharge
Elimination System (NPDES) permit program. NPDES
permit requirements currently apply to urban runoff
discharges from separate storm sewer systems of many
large municipalities and urban counties across the
country; to urban runoff discharged through a combined
sewer overflow; and to urban runoff discharges from
separate storm sewer outfalls that violate state water
quality standards.
Since urban runoff that enters water bodies from diffuse
or unidentifiable locations and sources can cause
significant water quality degradation, it certainly should
be addressed as part of a municipality's overall urban
runoff pollution prevention and control program.
To benefit fully from the nation's urban water resources,
widespread implementation of urban runoff pollution
prevention measures and controls is necessary. Unlike
point source control, however, institutional frameworks
and funding sources to deal with urban runoff pollution
are usually not well established, especially in smaller
communities.
Urban runoff pollution prevention and control programs
present unique challenges. Management and control
programs must often be developed and implemented at
the municipal level by local officials who might not be
familiar with the technical and regulatory issues
surrounding urban runoff pollution. The development of
an urban runoff pollution prevention and control plan
typically requires dealing with an extraordinary amount
of ambiguity. To illustrate this complexity, Table 1-1
compares various types of water resource improvement
projects. Municipal wastewater treatment projects are
driven by regulations and the NPDES program
requirements to control point sources with large,
typically end-of-pipe methods (biological or chemical
wastewater treatment), which generally do not call for
land use control or involvement of multiple agencies. At
the other end of the spectrum, urban runoff and
nonpoint sources are inherently difficult to address
because of the large number and types of diffuse
discharges, the quantity and effects of which are difficult
to assess. Control of such sources can require
structural BMPs, stricter regulations, more
comprehensive municipal maintenance programs, and
environmental education for homeowners and
businesses. (BMPs as used in this handbook can
indicate any type of pollution control measure, including
structural, regulatory, maintenance, education, or
others.) A successful local urban runoff pollution
prevention and control program depends on the
involvement and support of multiple entities including
federal agencies, state agencies, local government
departments, watershed protection groups, and private
citizens. Each of these groups has a stake in the
program's outcome and could have significant
resources to contribute.
The promulgation of EPA's storm water regulations and
the evolution and strengthening of other p'rograms, such
as those dealing with nonpoint source pollution (see
Chapter 2), reflect a trend—municipalities are being
required to address diffuse sources of pollution to
greater and greater degrees. These programs typically
emphasize management, rather than treatment, and
rely heavily on local control measures. Given the
complexity of urban runoff pollution control and the
typical scarcity of resources, municipal departments
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Table 1-1. Comparison of Water Quality Planning Projects
Project Type
Regulatory basis
Type and number of
pollutant sources
Reliability of
predicting pollutant
loads and impacts
Type of alternatives
Emphasis on
regulatory/land use
control
Agencies needed for
implementation
Engineering
Facilities
National
Environmental
Policy Act; State
Construction
Grant Program
One or few point
source(s)
High
Engineering
Limited
Few
CSO Facilities
EPA National
Strategy; State
CSO policies
Few to multiple
point sources
High
Engineering
with some BMPs
Limited
Few
Storm Water
Management
Storm Water
Permit Rule, 40
CFR Part 122
Few to multiple
piped and direct
discharges
Moderate
BMPs and
engineering
High
Some
Nonpoint
Source
Control
CWA,
Section 319
Multiple
nonpoint
sources
Low to
moderate
BMPs with
some
engineering
High
Many
Lake
Restoration
CWA,
Section 314
Multiple
: point and
nonpoint
sources
Moderate
BMPs and
, in-lake
High
Some
Watershed
Management
SDWA, Surface
Water Treatment
Rule
Multiple point
and nonpoint
sources
Low to moderate
Engineering,
BMPs, and in-lake
High
Many
must share responsibilities, and state and federal
agencies, as well as local groups, ideally should
network and build coalitions. Successful control efforts
require effective planning and decision-making to make
the best use of available resources. Identification of
high-priority problem areas and development of
effective pollution prevention and control strategies are
critical to a successful program.
Land development and intensive land use lead directly
to many of the pollution problems associated with urban
runoff. These problems can be divided into two basic
categories: hydrologic impacts and pollution.
Hydrologic Impacts of Urbanization
When precipitation contacts the ground surface, it can
take several paths. These include returning to the
atmosphere by evaporation; evapotranspiration, which
includes direct evaporation and transpiration from plant
surfaces; infiltration into the ground surface; retention
on the ground surface (ponding); and traveling over the
ground surface (runoff). Altering the surface that
precipitation contacts alters the fate and transport of the
runoff. Urbanization replaces permeable surfaces with
impervious surfaces (e.g., rooftops, roads, sidewalks,
and parking lots), which typically are designed to
remove rainfall as quickly as possible. As seen in Figure
1-1, increasing the proportion of paved areas decreases
the infiltration and evapotranspiration paths of
precipitation, thus increasing the amount of precipitation
leaving an area as runoff.
In addition to magnifying the volume of runoff, urban
development increases the peak runoff rate and
decreases travel time of the runoff. When mechanisms
that delay entry of runoff into receiving waters (i.e.,
vegetation) are replaced with systems designed to
remove and convey storm water from the surface, the
storm water's travel time to the receiving waters is
greatly reduced, as is the time required to discharge
the storm water generated by a storm. Figure 1-2
shows an urban area's typical predevelopment and
postdevelopment discharge rates over time.
The following changes to hydrology might be expected
for a developing watershed:
• Increased peak discharges (by a factor of 2 to 5).
• Increased volume of storm runoff.
• Decreased time for runoff to reach stream.
• Increased frequency and severity of flooding.
• Reduced streamflow during periods of prolonged dry
weather (loss of base flow).
• Greater runoff and stream velocity during storm
events.
Each of these hydrologic changes can lead to increased
pollutant transport and loading to receiving waters. As
peak discharge rates increase, erosion and channel
scouring become greater problems. Eroded sediments
carry nutrients, metals, and other pollutants. In addition,
increases in runoff volume result in greater discharges
of pollutants. Pollution problems, therefore, multiply with
increased urbanization.
Changes in hydrology affect receiving waters through
channel widening and subsequent streambank erosion
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100% —
80% —
60% —
40% —
20% —
Natural
cover
10-20%
paved
35-50%
paved
75-100%
paved
Legend
r".'.!".'.'..'".".'.l Evapotranspiration
I I Runoff
Infiltration
Figure 1-1. typical changes in runoff flow resulting from paved surfaces (MPCA, 1989).
Postdevelopment
Time
Figure 1-2. Pre- and postdevelopment hydraulics (MPCA, 1989).
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and deposition, increased stream elevation due to
greater discharge rates, and an increased amount of
sedimentary material within a stream due to streambank
erosion. The decrease in the ground surface's infiltration
capacity and loss of buffering vegetation undermines a
significant mechanism for pollutant removal, thereby
increasing the load entering the receiving waters.
Hydrologic changes can result in more subtle but
equally important impacts. Removal or loss of riparian
vegetation due to erosion, for example, can increase
stream temperature as levels of direct sunlight increase,
which can in turn change the biological community
structure. With increased sunlight, algae in nutrient-rich
receiving waters grow faster and the dominant species
changes, which affects the composition of higher
organisms. Increased imperviousness and loss of
ground-water resupply can lead to more frequent
low-flow conditions in perennial streams. The effects of
hydrologic changes due to urbanization therefore
should be prevented or mitigated to minimize urban
runoff pollution.
Further discussion of urban runoff hydrologic analysis
is presented in Chapter 6. Appendix A lists sources of
additional, more detailed information on the effects of
urbanization on runoff and stream hydrology.
Urban Runoff Pollution
Prevention and control of urban runoff pollution requires
an understanding of pollutant categories, of the major
urban sources of these pollutants, and of the pollutants'
effects. Table 1-2 lists the primary categories of urban
runoff pollutants, pollutants associated with each
category, typical urban runoff pollutant sources, and
potential effects. Table 1-3 summarizes the relative
contribution of predominant NFS pollution sources to
the degradation of U.S. rivers, lakes, and estuaries.
Additional pollutant sources often included in these
categories are shown in Table 1-2. For municipalities,
urban stormrgenerated runoff and construction are the
most prevalent sources; outlying agricultural activities
also can play a significant role in many urban areas.
The effects of urban runoff pollutants vary for different
water resource types. A given municipality's pollutants
of concern, therefore, depend on the types of water
resources in and downstream of the community, and
Table 1-2. Summary of Urban Runoff Pollutants
Category Parameters
Possible Sources
Effects
Sediments
Nutrients
Pathogens
Organic
enrichment
Toxic
pollutants
Organic and inorganic
Total suspended solids (TSS)
Turbidity
Dissolved solids
Nitrate
Nitrite
Ammonia
Organic nitrogen
Phosphate
Total phosphorus
Total coliforms
Fecal coliforms
Fecal streptococci
Viruses
E. Coli
Enterococcus
Biochemical oxygen demand (BOD)
Chemical oxygen demand (COD)
Total organic carbon (TOC)
Dissolved oxygen
Toxic trace metals
Toxic organics
Salts
Sodium chloride
Construction sites
Urban/agricultural runoff
CSOs
Landfills, septic fields
Urban/agricultural runoff
Landfills, septic fields
Atmospheric deposition
Erosion
Urban/agricultural runoff
Septic systems
Illicit sanitary connections
CSOs
Boat discharges
Domestic/wild animals
Urban/agricultural runoff
CSOs
Landfills, septic systems
Urban/agricultural runoff
Pesticides/herbicides
Underground storage tanks
Hazardous waste sites
Landfills
Illegal oil disposal
Industrial discharges
Urban runoff
Snowmelt
Turbidity
Habitat alteration
Recreational and aesthetic loss
Contaminant transport
Navigation/hydrology
Bank erosion
Surface waters
Algal blooms
Ammonia toxicity
Ground water
Nitrate toxicity
Ear/intestinal infections
Shellfish bed closure
Recreational/aesthetic loss
Dissolved oxygen depletion
Odors
Fish kills
Bioaccumulation in food chain
organisms and potential toxicity
to humans and other organisms
Vehicular corrosion
Contamination of drinking water
Harmful to salt-intolerant plants
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Table 1-3. Relative Contribution of Nonpoint Source Loading
(U.S. EPA, 1990a)
Relative Impacts, %
Source
Rivers Lakes Estuaries
Agriculture
Storm sawers/urban runoff*
Hydrotogical modification
Land disposal
Resource extraction
Construction
Silviculture
55.2
12.5
12.9
4.4
13.0
6.3
8.6
58.2
28.0
33.1
26.5
4.2
3.3
0.9
18.6
38.8
4.8
27.4
43.2
12.5
1.6
' Includes combined sewer overflows.
their desired uses. While conditions are very site
specific, the water resources generally most affected by
certain pollutants are discussed in the following sections.
Sediments
Sediment is made up of particulate matter that settles
and fills in the bottoms of ditches, streams, lakes, rivers,
and wetlands. Sediment loading occurs primarily from
soil erosion and runoff from construction sites, urban
land, agricultural areas, and streambanks. While some
sedimentation is natural, construction, farming, and
urbanization accelerate the process by increasing the
rates of storm water runoff, by removing cover
vegetation, and by changing slopes and affecting soil
stability. Increased runoff from developed areas
transports solids from various sources, including
deposition from erosion, litter (both manmade and
naturally produced), and road sanding. These solids
also carry nutrients, metals, and other substances that
can affect water resources adversely.
Sedimentation can have substantial biological,
chemical, and physical effects in receiving waters.
Solids can either remain in suspension and settle
slowly, or settle quickly to the bottom. Suspended solids
can make water look cloudy or turbid, diminishing a
water body's aesthetic and recreational qualities.
Decreased light penetration into the water column due
to increased turbidity reduces the growth of microscopic
atgae and submerged aquatic vegetation. Suspended
solids can also threaten the survival of filter-feeding
organisms (e.g., shellfish and small aquatic
invertebrates), which could stop feeding or feed less
efficiently. Sight-feeding predators (e.g., game fish and
microscopic predatory feeders) have trouble locating
prey In turbid waters and, as a result, can suffer from
Increased stress and decreased survival.
Deposited sediments that change the physical nature of
the bottom can greatly alter hydrology and habitat and
affect navigation. Sedentary, bottom-dwelling species
can be smothered by accumulating sediment, and the
habitat change can threaten many species that use the
bottom habitat to feed, spawn, or live. Depositional
sediments are also a sink for adsorbed pollutants,
such as nutrients, toxic metals, and organics, which
can affect both water-column and bottom-dwelling
organisms. These toxic pollutants can be remobilized if
sediments are disturbed and can pose a health hazard
to humans through the consumption of fish and
shellfish. Solids can cause problems in either the
suspended or the deposited state. While less of an
issue for ground water, solids can affect all surface
water resource types.
Nutrients
Runoff can contain high concentrations of nitrogen and
phosphorus, the nutrients of primary concern to water
quality. Nutrients are associated with agricultural and
urban runoff, atmospheric deposition, leachate from
landfills and septic systems, and erosion. Nutrient
additions can cause eutrophication, or over-enrichment,
of receiving waters, stimulating algal growth. In many
cases, nutrients from urban runoff originate from
chemical fertilizers and thus are in a dissolved form
which algae in the receiving waters can readily utilize.
Traditionally, phosphorus is considered the
growth-limiting nutrient in freshwater systems, while
nitrogen is considered growth-limiting in marine
systems. According to research in estuarine systems,
however, seasonal shifts can occur between nitrogen
and phosphorus enhancement of algal growth (D'Elia et
al., 1986a,b).
Nutrient enrichment can result in severe algal blooms,
either in the water column or in stream and lake beds
(by attached forms of algae). Blooms in the water
column can occur either as surface scums of blue-green
algae (e.g., Anacystis or Oscillatoria blooms) or
throughout the water column by numerous species of
floating algae. In all cases, blooms can be transported
by wind and currents, and are often concentrated along
the downwind shoreline; these blooms can cause
unpleasant odors and otherwise detract from the
aesthetic value of the water resource. High densities of
certain algal species can create taste and odor
problems in drinking water from reservoirs. Some
marine algal species potentially stimulated by
eutrophication of coastal waters contain toxins that can
be harmful to humans consuming affected fish or
shellfish. In addition to increased algal densities,
nutrient enrichment can lead to shifts in species
composition that can profoundly affect the transfer of
carbon through the food web (Sanders et al., 1987;
Duguay et al., 1989).
One of the most profound effects of eutrophication is
the depletion of dissolved oxygen in the water column.
6
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Algal cells from blooms and aquatic plants not utilized
as food by fish or other aquatic species eventually settle
to the bottom sediments. Bacterial decomposition of this
material consumes oxygen and can lead to anoxic
conditions (little or no dissolved acygen) in the
near-bottom waters. These conditions can persist for
months during the summer, damaging fish habitat,
creating odors, and releasing more nutrients from the
sediments. This phenomenon can occur on a small
scale, such as in a pond, small lake, or the quiescent
embayments of lakes and rivers used for spawning, or
on a very large scale such as in the Chesapeake Bay.
While mobile organisms, such as many species of fish,
can frequently move away from oxygen-stressed
waters, sessile organisms, such as shellfish, or fish
species that require high levels of oxygen, such as trout,
are at much higher risk. In highly nutrient-enriched
waters, a diurnal variation in dissolved oxygen
concentration might occur. During daylight hours, algae
produce oxygen through photosynthesis; then at night,
algae consume dissolved oxygen through endogenous
respiration.
Generally, nutrients cause problems that allow for the
development of algal blooms in slow-moving waters,
such as lakes, coastal areas, large rivers, and wetlands.
Nutrients are not considered a significant problem in
fast-moving urban streams, except when such streams
contribute nutrient loading to other water resources.
Pathogens
Pathogens are bacteria, protozoa, and viruses that can
cause disease in humans. Although not pathogenic
themselves, the presence of bacteria such as fecal
coliform or fecal enterococci are used as indicators of
pathogens and of potential risk to human health. While
detecting these indicator organisms in runoff does not
conclusively prove the presence of pathogens, no more
reliable system has been developed.
According to data from the Nationwide Urban Runoff
Program (NURP) study (U.S. EPA, 1983), urban runoff
typically contains fecal coliform densities of 10,000 (104)
to 100,000 (105) organisms per 100 milliliters. While
these high densities of indicator organisms do not
necessarily indicate the presence of pathogens,
potential health risks are associated with primary
contact recreation, such as swimming; with secondary
contact recreation, such as boating; and with
consumption of contaminated fish and shellfish in areas
affected by urban runoff.
The primary sources of bacterial and viral pathogens
are runoff from livestock in agricultural areas and runoff
from pet wastes and other contaminants in urban areas
(ASIWPCA, 1985). Other sources of these disease-
causing ;organisms include failed septic systems,
landfills, .bathers, combined sewer overflows, and
unauthorized sanitary sewer connections to storm
drains.
Pathogens generally cause water quality degradation in
slow-moving waterways and water resources used by
humans for primary and secondary contact recreation
or shellfishing. Pathogens are considered pollutants of
concern in drinking-water sources, slow-moving rivers,
lakes, and estuaries. Pathogen-contaminated discharges
to wetlands or to fast-moving urban streams are
typically less of a concern because of the lack of
recreational use and fishing in such waters.
Oxygen-Demanding Matter
As microorganisms consume organic matter deposited
in water bodies via storm-water runoff, oxygen is
depleted from the water. Organic enrichment can arise
from agricultural and urban runoff, combined sewer
overflows (CSOs), and leachate from septic tanks and
landfills. A sudden release of oxygen-demanding
substances into a water body during a storm can result
in total oxygen depletion and fish kills. Organic
enrichment can also have long-term effects on sediment
quality, increasing organic content and the tendency of
sediments to deplete surface waters and benthos of
oxygen, referred to as sediment oxygen demand (SOD).
The solid and dissolved organic content of water and its
potential to deplete oxygen is measured by its
biochemical oxygen demand (BOD).
Oxygen-demanding matter is primarily a concern in
water bodies that support aquatic life, such as rivers,
lakes, and estuaries. While generally a less important
consideration for fast-moving urban streams and
wetlands, high organic loads have been shown to cause
oxygen depletion in some urban streams.
Tox'rc Pollutants
Toxic pollutants include metals and organic chemicals.
Heavy metals in urban runoff result from sources such
as the breakdown of galvanized and chrome-plated
products (e.g., trash cans and car bumpers), vehicular
exhaust residue, and deicing agents. Potential sources
of toxic organic pollutants include vehicular residues,
industrial areas, landfills, hazardous waste sites,
leaking underground and aboveground fuel storage
tanks, and fertilizers and pesticides. In the NURP
studies (U.S. EPA, 1983), copper, lead, and zinc were
detected in more than 90 percent of storm water
samples from residential, commercial, and light
industrial sites; 14 toxic organic compounds were
detected in more than 10 percent of samples.
Potentially toxic compounds in urban runoff pollution
include oil and grease products from vehicles and
construction equipment. These products enter
waterways in runoff from roads, parking lots, service
-------
areas, and construction sites, and can be constituents
of landfill leachate. Such hydrocarbons frequently
become adsorbed to sediment particles and are
deposited in bottom sediments. These compounds are
toxic to aquatic organisms and can bioaccumulate in
fish and shellfish, potentially resulting in toxic effects to
humans consuming this tainted food. Because of the
potentially acute and chronic effects of toxic pollutants,
their discharge to all water resource types should be
limited.
Sodium and Chloride
Discharges of sodium and chloride to surface waters
result primarily from road salting during the winter, and
snowmelt during the early spring thaws. These
discharges can affect the taste of drinking water, can
harm people who require low sodium diets, and can
result in corrosion. Also affected are salt-intolerant plant
species. Sodium and chloride concentrations in runoff
are typically small enough to not cause serious
problems in water resources with continuous flushing
(e.g., in rivers and streams). Sodium and chloride
discharges are more of a concern in drinking-water
supplies and water resources that are not well flushed
(e.g., lakes and ground water).
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
ASIWPCA. 1985. Association of State and Interstate
Water Pollution Control Administrators. America's
clean water: the states' nonpoint source assessment.
Washington, DC.
D'EIia, C.F., J.G. Sanders, and W.R. Boynton. 1986a.
Nutrient enrichment and phytoplankton dynamics in
the Patuxent River estuary. Final Report to Maryland
Office of Environmental Programs. [UMCEES]
Chesapeake Biological Laboratory Ref. No. 86-30.
D'EIia, C.F., J.G. Sanders, and W.R. Boynton. 1986b.
Nutrient enrichment studies in a coastal plain estuary:
phytoplankton growth in large-scale continuous
cultures. Can. J. Fish Aquat. Sci. 43:397-406.
Duguay, L, G. Muller-Parker, S. Cibik, J. Love, J.
Sanders, and D. Capone. 1989. Effects of insolation
and nutrient loading on the response of natural
phytoplankton. Final Report to the Maryland
Department of the Environment. [UMCEES]
Chesapeake Biological Laboratory Ref. No. 89-134.
MPCA. 1989. Minnesota Pollution Control Authority.
Protecting water quality in urban areas: best
management practices for Minnesota. St. Paul, MN.
Sanders, J.G., S.J. Cibik, C.F. D'EIia, and W.R.
Boynton. 1987. Nutrient enrichment in a coastal plain
estuary: changes in phytoplankton species
composition. Can. J. Fish. Aquat. Sci. 44(1):83-90.
Schueler, T.R. 1987. Controlling urban runoff: a
practical manual for planning and designing urban
BMPs. Metropolitan Washington Council of
Governments Publication 87703.
Tourbier, J.T., and R. Westmacott. 1981. Water
resources protection technology. A handbook of
measures to protect water resources in land
development. Urban Land Institute, Washington, DC.
U.S. EPA. 1983. U.S. Environmental Protection Agency.
Results of the Nationwide Urban Runoff Program, vol.
1. Final report (NTIS PB84-185552). Washington, DC.
U.S. EPA. 1988. U.S. Environmental Protection Agency.
Guide for preparation of quality assurance project plans
for the National Estuary Program. Washington, DC.
U.S. EPA. 1990. U.S. Environmental Protection Agency.
National water quality inventory—1988 report to
Congress. EPA/440/4-90/003. Washington, DC.
U.S. EPA. 1991. U.S. Environmental Protection Agency.
Guidance manual for the preparation of part 1 of the
NPDES permit applications for discharges from
municipal separate storm sewer systems. EPA/505/
8-91/003A. Office of Water, Washington, DC.
U.S. EPA. 1992a. U.S. Environmental Protection
Agency. Storm water management for industrial
activities: developing pollution prevention plans and
best management practices. ERA/832/R-92/006.
Office of Water, Washington, DC.
U.S. EPA. 1992b. U.S. Environmental Protection
Agency. Storm water management for construction
activities: developing pollution prevention plans and
best management practices. EPA/832/R-92/005.
Office of Water, Washington, DC.
U.S. EPA. 1992c. U.S. Environmental Protection
Agency. Guidance manual for the preparation of part
2 of the NPDES permit applications for discharges
from municipal separate storm sewer systems.
EPA/833/B-92/002. Washington, DC.
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Chapter 2
Regulatory Framework
The structure of urban runoff regulations includes all
levels of government. Responsibility for enforcement
and oversight of these regulations can be held by
federal, state, local, or in some cases regional agencies.
Despite this array of programs and regulations, the
primary responsibility for developing approaches to
solve urban runoff pollution problems generally resides
with municipalities. Such pollution problems are
considered to be best handled locally because of the
site-specific nature of pollution sources and of potential
pollution prevention and control activities.
The major direction for prevention and control of urban
runoff pollution has come from the federal government
through the 1972 Clean Water Act (CWA) and its
amendments. Several sections of the Act deal with
diffuse source pollution. Additional federal statutes that
address urban runoff pollution include the Pollution
Preventiori Act, the Safe Drinking Water Act (SDWA),
and the Coastal Zone Management Act (CZMA).
This chapter discusses the major federal regulations,
policies, and programs related to urban runoff pollution
prevention and control. Given the national scope of this
handbook and the site-specific nature of state, regional,
and local regulations, this chapter focuses on
regulations and programs at the federal level. Currently,
the major federal statutes, regulations, and programs
that provide a framework for storm water runoff and
NPS pollution prevention and control are:
• Storm Water NPDES Permit Program
• Combined Sewer Overflow Strategy
• Pollution Prevention Act
• Safe Drinking Water Act
• Nonpoint Source Management Program
• Coastal Zone Nonpoint Source Pollution Control
• Clean Lakes Program
• National Estuary Program
• Agricultural Nonpoint Source Programs
This chapter includes a general discussion of each of
these statutes, regulations, and programs and of how
they relate to urban runoff pollution control at the
municipal level. Because of the dynamic, evolving
nature of most of these regulations and programs,
municipalities must keep up to date on specific
schedules and requirements. In addition, local officials
need to be familiar with urban runoff pollution prevention
and control programs initiated and overseen by state,
county, and local entities. These programs might stem
from federal regulatory authority but will be more
tailored and directly applicable to local issues and
needs.
Storm Water NPDES Permit Program
Under Section 402 of the 1972 CWA, point source
discharges of pollutants to navigable waters are
prohibited unless authorized by an NPDES permit.
Initially, the focus of the permit program was on point
source discharges of industrial and. municipal
wastewaters. As controls for point source discharges
were implemented, however, it became apparent that to
achieve the water quality goals of the CWA, more
diffuse sources of pollutants, including urban and
agricultural runoff, also would have to be addressed.
In the 1987 amendments to the CWA, Congress
introduced new provisions and reauthorized existing
programs that address diffuse sources. The
development of a workable program to regulate storm
water discharges was challenging given the number of
individual discharges, the diffuse nature of the sources
and related water quality effects, and limited state and
federal resources. After extended development and
review, EPA promulgated the NPDES storm water
regulations in November 1990. These regulations
represent the most comprehensive program to date for
controlling urban and industrial storm water runoff
pollution. The storm water regulations apply to
municipal separate storm sewer systems that serve
either incorporated populations greater than 100,000 or
unincorporated, urbanized populations greater than
100,000 based on the 1980 decennial census. In
addition, EPA defined a discharge associated with
industrial activity; activities that fall within 11 industrial
categories are required to obtain a NPDES storm water
permit (U.S. EPA, 1990a).
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The 1990 NPDES storm water permit regulations
directly affect approximately 200 municipalities and 47
counties across the country, as well as an estimated
125,000 industries and 10,000 construction sites
annually. Under this extensive program, affected
municipalities and industries must conduct storm water
runoff sampling and collect site characterization
information for each permit application. The municipal
permit application requirements include:
• Proof of the municipality's legal authority to enforce
the regulations.
* Characterization of the municipality's storm water
runoff through wet-weather sampling.
• Location of illicit storm drain connections and
development of a plan to eliminate those
connections.
• Description of existing urban runoff control programs
and development of a proposed storm water
management program.
• Analysis of the municipality's fiscal resources to
Implement the program.
Once a permit application is filed and a permit issued,
both municipalities and industries are required to
comply with permit conditions as specified by EPA or
the responsible state permitting authority. EPA has
developed general permits designed to cover many
industrial storm water discharges. These general
permits require the elimination of non-storm water
discharges from drainage systems and the
development of a storm water pollution prevention plan,
including:
* Development of a pollution prevention team.
• Description of sources expected to add pollution to
runoff.
• Implementation of source control practices, such as:
- good housekeeping,
— preventive maintenance,
— spill prevention and response procedures,
— equipment inspections,
— employee training,
- recording and internal reporting procedures,
— removal of non-storm water discharges,
— sediment and erosion control, and
- management of runoff.
• Implementation of annual site-compliance evaluations.
Most municipalities in the United States have
populations under 100,000 and therefore are not
currently required to file municipal storm water permit
applications. EPA is considering regulations to address
storm water runoff pollution from smaller communities
(CWA Section 402), which could be required to develop
storm water management plans. In addition, existing
NPDES regulations allow EPA or a responsible state
permitting authority to require permits for any storm
water discharges that cause violations of water quality
standards.
Combined Sewer Overflow Strategy
Combined sewer overflows (CSOs) are discharges from
sewer systems that are designed to carry storm water
rainfall and snowmelt runoff, along with sanitary
sewage, pretreated industrial wastewater, and a certain
quantity of flow from storm and ground-water infiltration.
Combined systems were constructed in more than
1,200 municipalities throughout the United States,
particularly in the Northeast, East, and Midwest.
Combined sewer systems have overflow points
designed to discharge wet-weather flows tfiat exceed
the carrying capacity of the system (usually designed to
carry peak dry-weather flow). Such combined sewer
discharges, if not treated before overflowing into
receiving waters, can significantly affect water
resources and threaten human health.
Many municipalities have begun to address these
pollution sources through various means, such as
storing and treating the discharges, implementing
low-cost BMPs, and replacing combined sewers with
separate sanitary and storm sewer systems. Separating
combined systems can be a long and relatively
expensive process and results in a separate storm
drainage system that could eventually require an
NPDES permit.
To address CSO discharges, EPA developed a national
strategy (Federal Register, 1989), which sets forth three
major objectives in NPDES permitting for CSOs:
• To ensure that no CSOs occur during dry-weather
flow conditions.
• To bring all wet-weather CSOs into compliance with
the technology-based requirements of the CWA and
applicable state water quality standards.
• To minimize impacts on water quality, aquatic biota,
and human health from wet-weather generated
overflows.
To achieve these objectives, recommended strategies
include the application of the best conventional pollutant
control technology (BCT), or best available technology
economically achievable (BAT), based on best
professional judgment (BPJ).
The technology-based effluent limitation for CSOs were
mandated to include six minimum technologies:
• Proper operation and maintenance
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• Maximization of collection system storage
• Pretreatment
• Maximization of flow to treatment plant
• Elimination of dry-weather overflows
• Control of solids and floatables
Following the development of a guidance document for
implementing the National CSO Strategy, three more
minimum technologies were added to the list:
• CSO inspection, monitoring, and reporting
• Pollution prevention
• Public notification of CSO impacts
EPA, with input from numerous state, municipal, and
environmental organizations, released a new Draft CSO
Control Policy on January 19,1993. The final policy will
provide guidance to permittees on developing
consistent CSO control strategies, and to NPDES
permitting authorities on developing permit language
and enforcement strategies that will ensure consistent
implementation of control strategies.
Pollution Prevention Act
With the passage of the Pollution Prevention Act of
1990, Congress established a national policy that
emphasizes pollution prevention over control or
treatment. With this policy, Congress defined a pollution
prevention hierarchy for all pollution reduction
programs:
• Pollution should be prevented or reduced at the
source whenever feasible.
• Pollution that cannot be prevented should be
recycled in an environmentally safe manner.
• Pollution that cannot be prevented or recycled should
be treated in an environmentally safe manner.
• Disposal or other release to the environment should
be a last resort and should be conducted in an
environmentally safe manner.
As stated in Chapter 1, one goal of this handbook is to
integrate pollution prevention into urban runoff pollution
control planning. Summarizing the goals of EPA's
pollution prevention program, the National Pollution
Prevention Strategy serves two basic purposes:
• To provide guidance and direction for incorporating
pollution prevention in EPA regulatory and
nonregulatory programs.
• To set forth a program that will achieve specific
pollution prevention objectives in a reasonable time
period.
To address the first objective, EPA is investigating
changes to the institutional barriers to pollution
prevention within the Agency by:
• Designating special assistants for pollution
prevention in each assistant administrator's office,
• Developing incentives and awards for Agency staff
who engage in pollution prevention efforts.
• Incorporating prevention into each program office's
comprehensive 4-year strategic plans.
• Providing pollution prevention training to Agency staff.
• Supporting technology innovation.
• Including prevention-related activities in the Agency's
operating guidance, accountability measures, and
regulatory review and development process.
To address the second objective, EPA is targeting
high-risk chemicals and seeking to reduce releases of
these chemicals through a voluntary program.
This pollution prevention policy was originally
developed to address industrial waste issues. Since it
also applies to storm water and diffuse source pollution,
EPA is now emphasizing pollution prevention at the
municipal level in dealing with urban runoff pollution.
Municipalities are encouraged to employ techniques
and policies that reduce the amount of pollutants
available for transport in urban runoff. Municipalities can
implement activities and use management practices
that are consistent with EPA's pollution prevention
policies. Such activities include public education;
household hazardous waste collection; location and
elimination of illicit connections to separate storm
systems; reduction of roadway sanding and salting; and
reduction of pesticide, herbicide, and fertilizer use. Such
programs, which are discussed in later chapters, can
reduce the availability of pollutants for washoff.
Safe Drinking Water Act
The Surface Water Treatment Rule (SWTR) of the
SDWA outlines requirements for watershed protection.
Municipalities that use surface water for drinking-water
supplies are required by EPA or the approved state
agency to develop a watershed protection plan for such
surface waters (AWWA, 1990). Municipalities are
required to:
• Develop a watershed description, including:
- the watershed's geographic location and physical
features;
- the location of major components of the water
system in the watershed;
- annual precipitation patterns, streamflow
characteristics, and other hydrology information;
11
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- agreements and delineation of land use and
ownership.
• Identify the watershed characteristics and activities
detrimental to water quality, such as:
- the effects of precipitation, terrain, soil types, and
land cover;
— the effects of animal population;
- point sources of contamination;
- nonpoint sources of contamination, such as road
construction, pesticides, logging, grazing animals,
and recreational activities.
• Control detrimental activities by implementing
appropriate control practices.
• Conduct ongoing routine and specific monitoring.
Under the SDWA, watershed control programs also
must:
• Minimize potential contamination by Giardia cysts
and viruses in the water source.
• Characterize the watershed hydrology and land
ownership.
• Identify watershed characteristics and activities that
threaten or harm source water quality.
* Monitor activities that threaten or harm source water
quality.
These watershed control programs are designed to
protect surface drinking water supplies from urban
runoff and NPS pollutants, and to reduce the need for
subsequent water treatment.
Nonpoint Source Management Program
A 1975 federal program designed to address NPS
pollution, called the 208 program, did not lead to
significant implementation. A more recent program,
initiated under the 1987 CWA amendments, is one of
the few federal programs that specifically addresses
and provides funding for NPS control. Through this
program under CWA Section 319, states must submit a
Nonpoint Source Assessment Report which:
• Identifies navigable waters that do not meet
applicable water quality standards.
• Identifies categories of nonpoint sources that add
significant pollution to the waters not meeting water
quality standards.
• Describes the process for identifying BMPs to
address the identified nonpoint sources.
• Identifies and describes state programs for controlling
pollution from identified nonpoint sources.
To be eligible for funding under CWA Section 319, states
can use the information in Nonpoint Source Assessment
Reports to develop and gain EPA approval for Nonpoint
Source Management Plans. These management plans
provide a framework to address the state's NPS control
issues and to develop priorities for implementation. At
a minimum, management plans must include:
• An identification of the BMPs selected to address the
nonpoint sources identified in the Assessment Report.
• An identification of the programs to implement these
BMPs.
• A schedule with annual milestones for program
implementation.
• A certification of existing adequate legal authority to
implement the program.
• A description of available federal and state funding
sources to be used.
Through CWA Section 319, EPA has the authority to
base annual NPS funding on its review and approval of
these management plans. EPA usually grants funds to
the state authority overseeing NPS control and allows
the state authority to earmark the funds for specific
programs, which are to be implemented on a watershed
basis to the maximum extent possible. The priorities set
in a state's management plan influence how the funds
will be spent each year. Depending on the state, funding
through this program could be available for a
municipality, or a group of municipalities, to implement
aspects of an NPS management program in a
high-priority watershed. Funds from this program,
however, are limited and are available mainly for
demonstration projects to educate or establish the
effectiveness of particular controls.
Coastal Zone Nonpoint Source Pollution
Control
Under Section 6217(g) of the 1990 Coastal Zone Act
Reauthorization, states with existing coastal zone
management programs are required to establish coastal
NPS programs approved by EPA and the National
Oceanic and Atmospheric Administration (NOAA).
These programs will be incorporated into the existing
state NPS management plans (CWA Section 319) and
state Coastal Zone Management Programs (CZMA
Section 306). The purpose of Section 6217(g) is to
encourage states to work with local authorities and
other states to develop and implement a program of
NPS pollution management to restore and protect
coastal waters (U.S. EPA, 1991). This program is limited
to NPS pollution control in coastal areas and the
contribution of inland sources of pollution to degraded
coastal water quality. In order to maintain a federally
12
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approved coastal zone program, states must act to
reduce NFS pollution through:
• Implementing EPA-specified management measures
and additional state-developed measures to control
NPS pollution in impaired or threatened coastal
waters.
• Modifying the state coastal zone boundary, if
necessary.
• Developing enforceable policies and mechanisms to
implement the Coastal Zone Act Reauthorization
management measures.
• Coordinating activities with existing CWA programs,
such as basin planning (Section 303), NPS planning
(Section 319), and the National Estuary Program
(Section 320).
• Developing a technical assistance program for local
governments and the public to implement the
management measures.
• Developing a public participation program.
The coastal NPS program can directly affect
municipalities in coastal areas with impaired or
threatened waters if they are not covered by the NPDES
municipal permit program (CWA Section 402). They will
likely be required by the state coastal NPS control
agency to implement management practices to address
NPS pollution. In addition, since this program includes
a requirement for states to reassess their coastal zone
boundaries, municipalities that formerly were not within
coastal areas might now be included.
EPA and NOAA, along with other federal and state
agencies, are developing guidance materials: a
document to assist states in developing their coastal
NPS pollution control program (U.S. EPA, 1991) and a
document specifying management measures for
controlling NPS pollution in coastal areas (U.S. EPA,
1993). This management measures guidance document
includes the following information for each management
measure discussed:
• A description of activity categories and applicable
locations.
• A listing of the pollutants addressed.
• A description of the water quality effects of
implementation.
• An outline of the expected pollutant reductions
achievable.
• A cost description.
• An outline of specific factors to be considered in
adapting management measures to specific sites.
The major management measure categories are
agriculture, forestry, urban, marinas and recreational
boating, hydromodification, shoreline erosion, and
wetlands. Where the proposed management measures
do not address pollution problems adequately, states
must develop additional management measures to
prevent and reduce nonpoint sources of pollution.
States with existing coastal zone management
programs will be required to implement management
measures in conformity with the approved NPS
measures. This requirement could result in additional
urban runoff pollution prevention and control
requirements on affected coastal municipalities.
Clean Lakes Program
The Clean Lakes Program, initiated in 1972 under CWA
Section 314, sets goals for defining the cause and
extent of pollution problems in each state's lakes and
for developing effective techniques to restore these
lakes. Lake protection or restoration projects should
include the development of watershed assessments
that consider all point and nonpoint sources affecting
lake quality. Each state is encouraged to organize and
administer its own lakes program and to apply for EPA
grants for lakes projects that meet state and EPA
criteria.
A review of statewide lake quality, to be part of the
biennial state Section 305(b) report, must include:
• Identification and classification of all publicly owned
lakes. ' '
« Description of the procedures, processes, and
methods to control sources of pollution.
• Description of the methods and procedures to restore
lake quality.
• Description of methods and procedures to control
high acidity.
« List of the lakes for which uses are known to be
impaired.
• Assessment of the water quality status and trends.
Clean Lakes projects are conducted in several phases:
a diagnostic/feasibility study, implementation of
recommendations, and long-term monitoring. The
diagnostic section of the study must consist of the
following information:
« Name, location, and hydrologic characteristics of the
lake to be studied.
• Geologic description of the drainage basin.
• Public access to the lake,
• Size and economic structure of the watershed's
population.
13
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• Summary of historical lake uses.
• Adverse impacts caused by lake degradation.
• Water uses of the lake.
• Point sources of pollution to the lake and abatement
actions to reduce this pollution.
* Land uses in the lake watershed.
• Discussion and analysis of historical baseline
limnological data and 1 year of current limnological
data as described in 40 CFR Part 35.
• Identification and discussion of biological resources
in the lake.
The feasibility section should include:
* Identification and discussion of pollution control
alternatives.
• Benefits expected from implementing the project.
* Long-term monitoring schedule.
• Proposed milestone implementation schedule.
• Description of how nonfederal funds will be obtained
for the project
• Relationship between the proposed lake project and
other water pollution control initiatives in the area.
• Summary of public participation in developing and
assessing the project.
* Operation and maintenance plan.
* Copies of all permits and impending permits
applicable to the project.
Once a diagnostic/feasibility report has been submitted
and approved, federal grants may be available to
implement project recommendations.
National Estuary Program
With the 1987 passage of CWA amendments (Section
320), Congress created the National Estuary Program
(NEP) to identify nationally significant estuaries, protect
and improve their water quality, and enhance their living
resources (U.S. EPA, 1990b). NEP estuary selection is
based on the estuaries' potential to include
environments of significant national concern and the
demonstrated commitment by involved local parties to
protect these valuable resources. Currently, 21
estuaries are part of the NEP (see Table 2-1). Common
problems found in these estuaries include pollution from
agricultural and urban runoff and waste disposal
activities, as well as high levels of toxins and pathogens,
excess nutrient loading, habitat loss, and declining
abundance of living marine resources.
Table 2-1. Estuaries in the National Estuary Program
as of 1993
Albemarle-Pamlico Sounds, NC
Buzzards Bay, MA
Casco Bay, ME
Chesapeake Bay, MD/PA/VA
Corpus Christi, TX
Delaware Bay, DE
Delaware Inland Bays, DE
Galveston Bay, TX
Indian River Lagoon, FL
Long Island Sound, CT/NY
Massachusetts Bay, MA
Narragansett Bay, Rl
New York/New Jersey Harbor,
NY/NJ
Peconic Bay, NY
Puget Sound, WA
San Francisco Bay, CA
San Juan Bay, PR
Santa Monica Bay, CA
Sarasota Bay, FL
Tampa Bay, FL
Tillamook Bay, OR
Once an estuary is accepted into the NEP, EPA formally
convenes a Management Conference of Agency and
local representatives to develop a Comprehensive
Conservation and Management Plan (CCMP) to protect
the estuary. The Management Conference must also
build support to carry out the CCMP recommended
actions, conduct extensive research, and implement
projects to improve the water quality of the estuary.
These projects are usually demonstration activities
implemented on a small scale, but can be applicable to
larger areas of an estuary.
The NEP is not specifically designed to address the
issue of NPS pollution. All 21 estuaries currently in the
program have identified storm water runoff and diffuse
source pollution as problems. Municipalities located
within an NEP estuary's watershed might be
encouraged as part of the CCMP, therefore, to address
diffuse source pollution issues. In addition, the NEP is
a potential funding source for urban runoff control
projects. Municipalities in the watersheds of major
coastal embayments should be aware of this program
and understand the management structure and
program objectives of local NEPs.
Agricultural Nonpoint Source Programs
While this handbook focuses primarily on storm water
and NPS pollution issues in urban watersheds, many
municipalities have outlying agricultural and other areas
that contribute solids, nutrients, pesticides, herbicides,
and pathogenic organisms to urban receiving waters. In
many areas of the country, a basinwide approach must
be taken to correct receiving-water impacts, and the
basin is likely to contain agricultural activities. The U.S.
Department of Agriculture (USDA) administers
programs that address agricultural NPS problems.
These programs are managed by the Soil Conservation
Service (SCS) and the Agricultural Stabilization
and Conservation Service (ASCS), which conduct
14
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research; undertake demonstration projects; develop
technologies; and provide education, technical
assistance, and funding (Margheim, 1990).
USDA programs do not set specific regulatory controls
on agricultural practices to prevent or reduce diffuse
source pollution. Rather, they provide technical
assistance and cost-sharing-based funding to farmers
for implementing agricultural BMPs, such as animal
waste control systems, conservation tillage, vegetative
buffer strips, and filter strips. Also, informational and
educational services are provided through these
programs by the Cooperative Extension Service.
Examples of USDA pollution control activities include:
• Conservation operations: Provides basic funding for
technical assistance to farmers, other landowners,
and units of government.
• Small watershed projects:. Provides planning,
technical, and financial assistance for implementation
of BMPs in small watersheds.
• Resource conservation and development projects:
Provides funding for personnel to coordinate
interorganizational cooperation and coordination on
certain environmental activities in designated
multicounty areas.
• Hydrologic unit areas: Provides technical assistance
to targeted agricultural watersheds to improve and
protect water quality.
• Demonstration projects: Provides funding for planning,
educational, technical, and financial assistance in
agricultural watersheds for demonstrating and
accelerating the adoption and implementation of new
and innovative technologies that emphasize protecting
ground water from agrichemicals.
• Agricultural conservation program: Shares cost of
implementing agricultural conservation practices
(BMPs) on farmland
• Special projects: Shares cost of implementing water
quality BMPs in identified watersheds.
• Other: Accelerate technical assistance to regional
projects such as National Estuary Programs; develop
and transfer water quality technology, training, and
public involvement; promote many locally oriented
and organized water quality projects (e.g., Lakes Lay
Monitoring Program, educational programs for
schools, conferences on wetlands and sludge, and
certification programs for pesticide use).
Summary
As demonstrated in this chapter, numerous regulations
address urban runoff pollution prevention and control at
the federal, state, and local levels. In planning a
program, all applicable regulations should be
considered and integrated. For example, the planning
process outlined in this handbook can be used to
develop plans to address pollution from separated or
combined systems, or where both systems exist. The
process applies to BMP programs both for CSO
problems and for separate storm water; in many
instances, both sources exist within the same
watershed. It can also be used in multijurisdictional
planning efforts where storm water, CSO,
drinking-water protection, or other elements are
controlled by different levels of state, regional, or local
government.
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
AWWA. 1990. American Water Works Association.
Guidance manual for compliance with the filtration
and disinfection requirements for public water
systems using surface water sources. (NTIS
PB90-148016). Washington, DC.
Federal Register. 1989. Fed. Reg. 54(173). Septembers.
Margheim, G.A. 1990. Making nonpoint pollution control
programs work, proceedings of a national
conference, April 23-26, 1989. National Association
of Conservation Districts. St. Louis, MO.
U.S. EPA. 1990a. U.S. Environmental Protection
Agency. NPDES permit application requirements for
storm water discharges. Final regulation: a summary.
October 31.
U.S. EPA. 1990b. U.S. Environmental Protection
Agency. Progress in the National Estuary Program,
report to Congress. EPA/503/9-90/005. Office of
Water, Washington, DC.
U.S. EPA. 1991. U.S. Environmental Protection Agency.
Coastal Nonpoint Pollution Control Program: program
development and approval guidance. Office of Water,
Washington, DC.
U.S. EPA. 1993. U.S. Environmental Protection Agency.
Guidance specifying management measures for
sources of nonpoint pollution in coastal waters.
EPA/840/B-92/002. Office of Water, Washington, DC.
15
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Chapter 3
The Planning Process
This chapter outlines the process for developing and
initiating urban runoff pollution prevention and control
plans. It also discusses the establishment and
refinement of program goals. Each step in the planning
process is discussed separately and in detail in
subsequent chapters.
Description of the Planning Process
The planning process for urban runoff pollution
prevention and control programs presented in this
handbook is based on regulations that require such
programs and on technical literature about planning
approaches. Table 3-1 compares planning approaches
required by various regulations. Despite the increasing
complexities and uncertainties as one proceeds from
left to right in the matrix (as was demonstrated in Table
1-1), the required planning approaches are similar. The
process generally consists of the following major
components:
• Determining existing conditions: Analyzing existing
watershed and water resource data and collecting
additional data to fill gaps in existing knowledge.
• Quantifying pollution sources and effects: Utilizing
assessment tools and models to determine source
flows and contaminant loads, extent of impacfs, and
level of control needed.
• Assessing alternatives: Determining the optimum mix
of prevention and treatment practices to address the
problems of concern.
• Developing and implementing the recommended
plan: Defining the selected system of prevention and
treatment practices for addressing the pollution
problems of concern and developing a plan for
implementing those practices.
Table 3-1. Planning Approaches Defined in Regulatory Programs
Project Type
Regulatory basis
Determining
existing conditions
Quantifying
pollution sources
and water
resource impacts
Assessing
alternatives
Developing and
implementing the
recommended plan
Engineering
Facilities
National
Environmental
Policy Act
Describe existing
system
Develop planning
criteria
Collect and
analyze data
Develop
alternatives
Assess
alternatives
Develop
recommended
plan
Develop
implementation
plan
CSO Facilities
National CSO
Strategy (8/89)
Describe existing
conditions
Collect and
analyze data
Develop
alternatives
Assess
alternatives
Develop
recommended
plan
Develop
implementation
plan
Storm Water
Management
Storm Water
Permit Rule, 40
CFR 122
Describe existing
conditions
Collect and
analyze data
Developing
alternatives
Assess
alternatives
Develop
management plan
Develop
implementation
plan
Nonpoint
Source Control
CWA, Section
319
Analyze existing
conditions
Collect and
analyze data
Identify and rank
problems
Screen BMPs
Select BMPs
Develop ~
recommended
plan
Develop
implementation
plan
Lake Restoration
CWA, Section
314
Describe
environmental
conditions
Conduct
diagnostic survey
Conduct
feasibility study
Develop
recommended
plan
Develop
implementation
plan
Watershed
Management
SDWA
Develop
watershed
description
Identify
detrimental
characteristics
Conduct risk
assessment
Develop
detrimental
activities control
plan
17
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Each regulatory program outlined in Table 3-1
addresses the same components of water quality
planning but uses different language to describe the
process of each component
For example, as a result of the differing regulatory
approaches, municipalities might independently
conduct CSO and storm water planning. Yet since these
sources of pollution often exist in the same watersheds
and affect the same water resources, this fractured
approach is not desirable. To address urban runoff
pollution control effectively, communities must consider
multiple pollution sources in planning using a watershed
approach. Table 3-2 lists selected planning processes
outlined in the literature, which tend to resemble those
required by the regulations cited in Table 3-1. The
planning process described in this handbook has been
developed to be consistent with regulatory requirements
as well as technical literature.
The planning approach used in this handbook (see
Figure 3-1) is intended to offer municipal officials a
systematic approach to developing an urban runoff
pollution prevention and control plan. In general, the
planning process proceeds as follows:
1. Initiate program (Chapter 3)
2. Determine existing conditions (Chapter 4)
3. Set site-specific goals
Tablo 3-2. Planning Approaches Defined in the Literature
Literature
Reference
Determining
existing conditions
Quantifying
pollution sources
and effects
Assessing
alternates
Urban Surface
Water
Management
(Walesh, 1989)
Establish
objectives and
standards
Conduct Inventory
Analyze data and
prepare forecasts
Formulate
alternatives
Compare
alternatives and
select
recommended
plan
Developing the
Watershed Plan
(U.S. EPA, 1991a)
Identify problems
and opportunities
and determine
objectives
Develop resource
data
Interpret, analyze,
and evaluate data
and forecasts
Formulate and
evaluate
alternatives
Evaluate and
compare
alternatives
Developing Goals
for Nonpoint
Source Water
Quality Projects
(U.S. EPA,
1991 b)
Inventory
resources and
forecast conditions
Identify problems
Develop goals or
objectives
Formulate
alternatives
Evaluate
alternatives
Santa Clara
Valley Nonpoint
Source
Study — Volume II:
NPS Control
Program.
(SCVWD, 1990)
Initiate public
participation
Define existing
conditions
Review regulatory
problems
Define goals and
objectives
Define and
describe problems
Identify NPS
control measures
Evaluate control
measures
Develop evaluation
criteria
State of
California Storm
Water Best
Management
Practice
Handbooks
(CDM, 1993)
Define goals
Assess existing
conditions
Set priorities
Select near-term
BMPs
Urban
Stormwater
Management
and
Technology:
Update and
Users' Guide
(U.S. EPA, 1977)
Assess existing
data
Compare
conditions vs.
objectives
Determine extent
of runoff problem
Conduct
selective field
monitoring
Refine problem
estimates
Assess
alternatives
Examine and
screen measures
Select measures
Developing and
Implementing the
recommended
plan
Prepare plan
implementation
program
Implement plan
Select alternative Select best
and record decision alternative and
record decision
Reassessment of
measures
Recommend
control measures
and
implementation
program
Implement Determine
near-term program attainable
improvements
Assess program
effectiveness
18
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Program Activities
Technical Activities
Set general
program goals
Set site-specific
program goals
Refine site-
specific program
goals
Monitor program
effectiveness
Initiate
program
(Chapter 3)
Determine
existing conditions
(Chapter 4)
Collect and analyze
additional data
(Chapter 5)
Assess and
rank problems
(Chapter 6)
Screen BMPs
(Chapter?)
I
Select BMPs
(Chapter 8)
Implement plan
(Chapter 9)
Figure 3-1. Urban runoff pollution prevention and control planning process.
19
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4. Collect and analyze additional data (Chapter 5)
5. Refine site-specific goals
6. Assess and rank problems (Chapter 6)
7. Screen BMPs (Chapter 7)
8. Select BMPs (Chapter 8)
9. Implement plan (Chapter 9)
While the planning process generally is intended to be
followed in sequence, the process can always be
altered depending on the specific situation. For
example, a municipality might already have begun
planning to address certain sources (e.g., storm water
or CSOs). In such cases, starting later in this planning
process or integrating other sources into the ongoing
planning might be more efficient.
Goal setting and refinement is more appropriately
shown as a parallel process rather than a specific step.
Only very general goals should be considered at the
outset of a program. Existing data should be assessed
before setting any site-specific goals. As new data are
analyzed, new findings and issues are likely to emerge.
Program goals therefore must be reevaluated as
the planning process progresses. Monitoring the
effectiveness of what has been implemented is very
Important. Since further planning typically will be
required, the point of reentry in the planning process
needs to be flexible.
The remainder of this chapter describes each step of
the planning process in greater detail. The chapter ends
with a case study showing the process of setting and
refining program goals for Lewiston, Maine.
Initiate Program
As a first step in the planning process, municipal
officials undertaking urban runoff pollution prevention
and control planning should develop an overall program
structure. Early considerations include organizing a
program team; establishing communication, coordination,
and control procedures for members of the planning
team and other participants; identifying tasks and
estimating the number and types of personnel and other
resources for each task; and scheduling tasks (Walesh,
1989).
For local urban runoff pollution prevention and control
programs, the program team should be made up of
municipal personnel: public works personnel;
conservation officials; engineering personnel; parks
personnel; and planning and other officials who
regularly deal with or control issues such as utilities,
land use and zoning, development review, and
environmental issues. The team should be
muttidisciplinary and able to address the engineering,
land use, and environmental issues that will need to be
resolved. It is important to involve all entities, including
political officials and the public, who have a stake in the
program outcome. To win support for the end result, a
shared ownership of the process is necessary. Given
that municipal boundaries typically do not coincide with
watershed boundaries, individuals from all affected
communities should be involved in the program.
Depending on the size and complexity of the program,
private consulting resources might also be necessary.
In addition, involving officials of other agencies at the
county, state, and federal levels is prudent, especially if
one of these agencies is directly responsible for
controlling sources within the watershed. Also, such
agencies might have regulatory oversight and might be
able to contribute funding or provide technical
assistance. Based on their potential contribution to the
program, their role could consist of participation on a
technical or management advisory group. Further
discussion on program team composition is provided in
Chapter 9.
Initiating the program also includes establishing the
program management tasks necessary for successful
program execution. Methods of project management
and control might already be in effect in the municipality
or may be developed specifically for the program,
particularly in the case of multiagency involvement.
These tasks include estimating, forecasting, budgeting,
and controlling costs; planning, estimating, and scheduling
the program activities; developing and evaluating quality
control practices; and developing and controlling the
program scope. The program team also will have to
develop a funding plan, as well as a public information,
education, and outreach program.
Once the program team is assembled and the program
is structured, the remaining portions of the planning
process can be undertaken.
Goal Setting
Setting goals is a key aspect of the planning process,
and refining goals is an ongoing consideration. Projects
such as those discussed in this handbook, some of
which deal with multiple point and nonpoint sources,
require an integrated urban runoff management
program, including flood, drainage, and pollution
prevention and control. Successful implementation of
these programs depends on establishing clear goals
and objectives that are quantitative, measurable, and
flexible (U.S. EPA, 1991c). Setting goals is a process
that moves from less to more specificity as additional
information on the watershed and water resources is
obtained. Figure 3-1 shows the iterative nature of
setting program goals as the planning process
proceeds. As noted earlier, site-specific goals should
not be set at least until existing conditions are assessed.
20
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Types of Goals
The two main types of urban runoff goals are water
resource- and technology-based goals. Water
resource-based goals are based on receiving-water
standards which consist of designated uses and criteria
to protect these uses. For example, water
resource-based goals may relate to uses, such as
"opening half of the currently closed shellfish beds."
They also may consist of more specific pollution
reduction goals, such as lowering the Trophic State
Index or reducing the number of oxygen-demanding
substances in a lake. In addition, water resource-based
goals can place numerical limits on the concentrations
of specific pollutants. Further, examples of water
resource-based goals include no degradation, no
significant degradation, and meeting water quality
standards! As a defining characteristic of water
resource-based goals, the success in meeting such a
goal is determined by the condition of the water
resource. Applying water resource goals to urban runoff
problems, however, might be difficult since water quality
standards would need to be assigned to intermittent and
variable events.
In contrast, technology-based goals require specific
pollution prevention or control measures to address
water resource problems. They can be very general,
such as "implement the nine minimum technologies for
CSO control," or very specific, such as "implementing
runoff detention at 50 percent of the industrial sites in a
watershed." A municipality might be able to determine
the effectiveness of implementing these goals without
conducting future water quality monitoring. With most
technology-based goals, implementing the control
measures is presumed to be adequate to protect water
resources. Monitoring, however, is still essential after
implementation to gauge the program's effectiveness
and to see if the desired environmental results are being
achieved.
The types of goals set by a municipality usually depend
on the natural or political forces driving urban runoff
control and the public's level of knowledge about the
affected water body. If a community undertakes an
urban runoff pollution prevention and control program
because it has lost a resource (e.g., closed shellfish
beds or loss of fishing or swimming areas), the
community usually will set a water quality-based goal
linked directly to recovering the resource. If a
community expects to lose a resource from a known
source (e.g., a farm located directly on a stream or
frequent oil spills from an industrial plant), its goal can
be specific and technology-based. On the other hand,
communities that are not currently suffering from
obvious problems with a water resource might launch
urban runoff pollution prevention and control programs
only to comply with regulations (see Chapter 2). These
communities might not know or be aware of existing or
potential water quality problems. Even under these
conditions, however, setting general goals, such as "to
meet the requirements of the regulations," is not only
possible, but important. Even this general goal directs
the program's focus, which then can be made more
specific as more information is obtained. In these cases,
the municipality typically has to rely on state-mandated
goals for the specific water body of concern or general
state mandates for the condition of all water bodies.
Although the water resource- and technology<-based
goals discussed above differ in specificity and
complexity, they are all valid for an urban runoff pollution
prevention and control plan. Goal-setting will focus the
scope of work throughout a program.
Reassessing Goals
Far from static statements, water resource- or
technology-based goals should be reassessed as
appropriate in the planning process. Once early goals
have been stated for a watershed or receiving water, all
future actions affecting these resources can be
considered against this backdrop and the goals can be
reassessed. As more information is gathered, the goals
can be maintained, made more specific, or changed
completely. By the time the program is defined and
ready to be implemented, however, fairly specific goals
should exist so that program evaluators can determine
whether or not goals have been met.
Determine Existing Conditions
After initiating the program, the planning team must
develop a greater understanding of existing watershed
characteristics and water resource conditions in order
to:
• Define existing conditions pertinent to the urban
runoff pollution prevention and control program.
• Identify data gaps.
• Maximize use of existing available information and
data.
• Organize a diverse set of information in a useable
way.
The required research is typically done by gathering
existing available watershed information (e.g.,
environmental, infrastructure, municipal, and pollution
source information), as well as receiving-water data
(e.g., hydrologic, chemical, and biological data, and
water quality standards and criteria). This information
can be obtained from various data bases, mapping
resources, and federal, state, and local agencies. The
information can then be used to develop watershed
maps; to determine water, sediment, and biological
quality; and to establish the current status of streams,
21
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rivers, and other natural resources. Once these data are
gathered, the program team can organize the
information into a coherent description of existing
conditions and determine gaps in knowledge. In this
way, the existing conditions of the watershed and
receiving waters can be defined. This step in the
planning process is discussed in Chapter 4.
Collect and Analyze Additional Data
Even under the best circumstances, municipalities
usually will not have all the required information to
describe adequately a program area's existing
conditions. The program team, therefore, might have to
gather additional information through field investigation
and data collection. With this additional information and
existing data, the program team can evaluate more fully
the existing conditions of the watersheds and water
resources of concern. Given the cost and time involved
in data gathering, the program team will have to weigh
the benefits of additional data collection against using
limited funds for plan development and implementation.
If the additional data are required, a plan to gather these
data must be developed. The plan should include
an assessment of available staffing and analytical
resources; identification of sampling stations, frequencies,
and parameters for sampling and analysis; development
of a plan to manage, analyze, and interpret the collected
data; and analysis of available or needed financial
resources. This step in the planning process is
presented in Chapter 5.
Assess and Rank Problems
Once sufficient data have been collected and analyzed,
the data can then be used to assess and rank the
pollution problems. Based on data gathered in earlier
steps, the team will need to develop a list of criteria to
assess problems. These criteria are used in conjunction
with water quality assessment methods and models
to determine current impacts and future desired
conditions.
Having determined the problems of concern, the project
team can rank these problems to set priorities for the
selection and implementation of pollution prevention
and control measures. The emphasis on ranking of
resources and problems is central to EPA's NPS
strategy. This concept assumes that focusing resources
on targeted areas or sources enhances water resource
improvement. Further, it assumes that demonstrating
water resource benefits increases public support of
urban runoff pollution prevention and control programs
as citizens become more closely attuned to overall
water quality goals (U.S. EPA, 1987). The municipality,
therefore, should investigate the sources of pollution
affecting the high-priority water bodies to determine the
order in which to address these, problem sources. In
many cases, an analysis at the sub-basin level is
needed to determine which areas of a watershed
contribute the greatest loadings. The data gathered in
the previous step will be particularly useful in this
assessment. Also, municipalities should investigate
water resources within their region to develop priorities
so that limited resources can be targeted to areas with
greatest potential for improvement. Various levels of
detail can be used in this assessment, ranging from
simple unit load methods to complex computer models.
This ranking procedure, one of the more subjective and
difficult steps in the urban runoff planning process,
is described in Chapter 6, along with problem
assessment.
As additional data are collected and evaluated, the
program team should refine the goals of the program
and make them more specific. For example, at the
beginning of the program, the municipality might have
been aware of excessive algal blooms in a lake but
might not know the cause. An initial goal of the pollution
prevention and control program might have been simply
to eliminate these algal blooms. After further
investigation and water quality sampling, the
municipality might discover that continuous high
phosphorus loadings are directly contributing to the
algal blooms. The goal could then be made more
specific by focusing on reducing or eliminating
phosphorus sources. The initial goal, rather than being
abandoned in favor of another goal, is refined to focus
future actions on the specific causes of the water
resource impairment.
Screen Best Management Practices
Once the water resource problems have been
prioritized, specific water resource problems and their
sources can be addressed. The program team should
compile a list of various pollution prevention and
treatment practices and review them for their
effectiveness in solving the prioritized problems. To
assist the municipality in gathering information on
various practices, Chapter 7 includes brief descriptions
of various nonstructural and structural practices, and
includes references for additional information. Also
described is the initial BMP screening step, when
potential practices are reviewed for their applicability to
the watershed and water resource problems of concern.
While the team initially faces a large number of potential
practices, obviously inappropriate practices are
eliminated in this step based on criteria such as the
primary pollutants removed, drainage area served, soil
conditions, land requirements, and institutional
structure. Following this initial screening, the program
team will have a list of potential practices to be
evaluated further.
22
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Select Best Management Practices
During this step, the program team investigates the list
of potential pollution prevention and treatment practices
developed from the previous step to determine which to
include in the plan. More specific criteria should be used
for analyzing these potential practices than during the
initial screening. To make the final selection, the
program team must use the analytical tools developed
during the ranking and assessment of problems, as well
as decision factors such as cost, program goals,
environmental effects, and public acceptance. As with
the initial screening step, these evaluation criteria
depend on established priorities. Generally, the
selection process yields a recommended system of
various pollution prevention and treatment practices
which together address the pollution sources of
concern. Availability of required resources to implement
the practices is a major consideration. If needs and
resources don't match, the municipality might have to
adjust its expectations to what realistically can be
accomplished. Both structural and nonstructural
practices might be required. This step in the planning
process is discussed in Chapter 8.
Implement Plan
After choosing pollution prevention and treatment
practices, the program team moves from planning to
implementation, which often occurs through a phased
approach. Inexpensive and well-developed practices
can be implemented early in the program as pilot or
demonstration studies; and these results might
influence further implementation. Given the added
requirements of implementation, operation, and
maintenance, the original program team might expand
to include members with more construction experience.
Also, funding sources are needed for initial capital
expenses and continuing operation and maintenance
costs. Nonstructural practices must be implemented,
and the team must arrange for the detailed design and
construction:of structural practices.
During this step, program responsibilities must be
clearly delineated. All involved entities must be familiar
with and accept their role in implementing and enforcing
the plan. Continuing activities also should be clearly
defined and monitoring schedules should be set to
determine the program's effectiveness in meeting its
goals. Maintenance programs should be developed so
that structural practices continue to operate as
intended. Finally, the municipality should be aware of
available federal and state technical assistance that
could help throughout implementation of the plan. This
step in the planning process is discussed in Chapter 9.
Summary
This handbook is based on the process outlined in this
chapter. The process includes setting goals, analyzing
existing data, collecting and analyzing additional data,
assessing and ranking problems, screening BMPs,
selecting BMPs, and defining and implementing the
plan. The process is founded on approaches described
both in technical literature and in regulatory
requirements. Each step should be followed to develop
an effective and realistic urban runoff , pollution
prevention and control program.
Developing and implementing an urban runoff pollution
prevention and control program at the municipal level is
a multidisciplinary effort that requires a program team
that has varied experience and is familiar with program
requirements. The process presented in this handbook
is designed to provide program teams with a
step-by-step approach to conducting these types of
planning programs.
Planning, however, is only the first phase in the
protection of water resources. The program team
should keep in mind the ultimate goals of the program.
Since implementation and program assessment are
important, the setting and refinement of program goals
is key. By reaching an early consensus on program
goals and reassessing goals during the process, the
program team can increase the possibility of successful
implementation. During the planning process,
increasing knowledge about the area's water resources
and characteristics of the watersheds should be
emphasized. All these steps are important to the
program's ultimate success.
The following case study outlines some of the initial
steps in program development and initial goal setting for
Lewiston, Maine.
23
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Case Study:
City of Lewiston, Maine,
CSO, Storm Water, and Nonpoint Source Planning Program
Background
The city of Lewiston, situated on the Androscoggin River, is Maine's second largest city. Lewiston and
its sister city, Auburn, serve as the industrial, commercial, and service center for Maine's southern,
central, and western regions. With a population of about 40,000, Lewiston has a combination of
residential, commercial, industrial, and parkland use with limited agricultural land. It has seven
watersheds that will be described later.
In 1991, Lewiston launched a planning program to address issues such as CSO impacts, storm water
management, and nonpoint source control. Known as the city's Clean Water Act master planning
program, the effort was undertaken for a number of reasons: Maine required the city to develop a facilities
plan for CSO abatement, and there was potential for development of new storm water and NPS
requirements at the state and federal levels. Incorporating these considerations into an overall planning
effort_a proactive approach—would meet requirements of existing regulations and prepare the city for
future requirements. By undertaking a program consistent with watershed needs, Lewiston chose a
comprehensive rather than fragmented approach based on different, and possibly conflicting and
overlapping, regulatory requirements. The city also decided to set water resource-based goals that would
be as consistent as possible despite the changing regulatory environment.
Program Initiation
The city's public works department assumed responsibility for the program and formed a team that would
meet regularly and guide the planning process. The team included individuals from:
• Department of Public Works
• Planning Department
• Lewiston-Auburn Water Pollution Control Authority
• Highway Department
• General public
The public works department assigned a staff person who expended a significant amount of his time to
support the effort. The department also secured funding (100% from city funds), developed a scope of
services, and hired an engineering consultant to perform technical tasks and provide services which
were beyond Lewiston's capability or available resources.
Regulatory Setting
One of the program team's first tasks was to compile information on current federal and state regulations
that potentially pertained to the planning effort. A series of contacts were made, especially with state
regulatory personnel, to determine the status of regulatory activities. Information on current regulatory
setting was reviewed (as summarized in Table 3-3) and appropriate state regulatory personnel were
identified. Changes were occurring in several areas, especially CSO and storm water, that needed to
be monitored and incorporated into the program.
Set Initial Program Goals
Using available data, initial goals were developed along with assessment of existing conditions. This
assessment is described in a companion case study at the end of Chapter 4. A basic goal was that the
program should result in an understanding of and compliance with current and upcoming regulations
related to CSO, storm water, and NPS control. Initial goals were also established for each major
watershed. The watersheds are shown in Figure 3-2, and their characteristics are listed in Table 3-4.
24
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Table 3-3. Federal and State Regulation of Urban Runoff
Regulation Federal
State
Combined Sewer Overflows
Storm Water NPDES Permits
Pollution Prevention Act
Safe Drinking Water Act
Nonpoint Source Pollution
Regulations
Coastal Zone Nonpoint Source
Pollution Control
Clean Lakes Program
National Estuary Program
Agricultural Nonpoint Source
Programs
Comprehensive Planning/Growth
Management
Shoreland Zoning
National policy (currently under review)
CWA, Section 402 NPDES regulations
National Pollution Prevention Strategy
Surface Water Treatment Rule
CWA, Section 319
Coastal Zone Management Act, Section
6217(g)
CWA, Section 314
CWA, Section 320
Funding and guidance provided at the
state level through SCS
Not applicable
Not applicable
State CSO policy (approved by EPA)
General permit (does not currently affect
Lewiston)
Future impacts
Municipal permits
Municipally owned industrial facilities
Not applicable
State allows variance; however, not
applicable to Lewiston
General guidance from state NPS office
Probably not applicable (coastal
boundaries not yet determined)
Limited funding for state program
Lewiston and Auburn in upper reaches of
Casco Bay watershed; CCMP being
developed
SCS assistance to farms; no significant
farms in city
Growth management plans required;
Lewiston obtained approval
Requires special zoning practices within
75 ft of streams and 250 ft of other water
bodies; Lewiston obtained approval
Watershed boundaries
Streams
Figure 3-2. Watersheds in Lewiston, Maine.
25
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Table 3-4. Land Use Near Major Watersheds in Lewiston, Maine
Watershed Name Size, ac Land Use Description
No-Name Pond
No-Name Brook
Stetson Brook
Hart/Goff Brooks
Salmon/Moody Brooks
Japson Brook
Androsooggin River
750 Rural/residential, shore line cottages
10,000 Mainly undeveloped, some residential
3,000 Rural, residential, and commercial/industrial
1,600 Residential, commercial, and industrial
1,900 Primarily undeveloped, minor agriculture
1,500 Residential and institutional
2,300 Urban in central core, undeveloped or industrial In outlying area
The program team held a workshop to facilitate discussion and obtain input on the city's water resources
and appropriate initial program goals. A form similar to that shown in Table 3-5 was used to compile the
information. Each watershed was discussed, including its water quality classifications, current uses,
known problems, desired uses, and goals. A qualitative assessment or ranking of the individual
watersheds was included to indicate the relative importance of the water resources to the city. This
procedure was done to assist later decision-making which could involve setting priorities for funding or
phasing of activities.
Table 3-5. City of Lewiston Initial Water Resources Goals
Watershed Water Quality
Name Classification
No-Name A
Pond
No-Name C
Brook
Stetson Brook B
Hart and B
Goff Brooks
Salmon/Moody B
Brook
Jepson Brook B
Androsooggin C
River
Ground water GWA*
Current Uses
Aesthetics
Recreation-fishing,
boating
Aesthetics
Aesthetics
Aesthetics
Aesthetics
Drainage
Aesthetics
Recreation-fishing,
boating
Drinking water
supply (for town of
Lisbon)
Known
Problems
Algal blooms
Septic tank
discharges
Erosion (use
of ATVs)
Debris
Erosion
CSOs (one)
Erosion
Industrial
areas
Interceptor
sewer
surcharging
Agriculture
CSOs (no
visual/odor)
Debris
Point
sources
(paper mills)
Erosion
(gravel pits)
CSOs
None known
Qualitative
Assessment
of Importance
Most important
town water
resource
Second most
important town
water resource
Third most
important town
water resource
Fourth most
important town
water resource
Small
watercourses of
minor
importance
Channelized
drainage ditch
Large regional
water resource
Currently of
limited
importance to
town
Desired
Uses
Same
Same
Same, plus
fishing
Same
Same
Same
Same
Same
Goals
Maintain and protect
existing uses
Maintain and protect
existing uses
Upgrade to Class B
Meet Class B
standards
Meet Class B
standards
Meet Class B
standards
Maintain current use
Meet Class C
standards
Maintain and protect
existing uses
* Ground-water classification A.
26
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While the initial goals were recognized as expensive and potentially not attainable in the near future,
the interactive process was desirable when feasible in terms of cost and effort. Moreover, the goals could
be revised if unrealistic. Consideration was given to the existing regulatory requirements in the water
quality standards (see Table 3-6). The main differences in water quality criteria for each classification
are for dissolved oxygen and E. coll bacteria.
Table 3-6. Comparison of Maine Water Quality Standards
Minimum Dissolved
Oxygen
E. coli Bacteria
Classification
AA
A
r
Designated Uses
Drinking water (with disinfection); fishing; primary
and secondary contact recreation; free-flowing
and natural habitat for fish and other aquatic life'
Drinking water (with disinfection); fishing; primary
and secondary contact recreation; industrial
process and cooling water; hydroelectric power
generation; navigation; natural habitat for fish
and other aquatic life
mg/L
As
naturally
occurs
7.0
%
Saturation
As
naturally
occurs
75
Geometric
Mean
NoJIOO mL
As
naturally
occurs
As
naturally
occurs
Single
Sample
NoJIOOmL
As
naturally
occurs
As
naturally
occurs
B Drinking water (with treatment); fishing; primary 7.0* 75a 84b 427b
and secondary contact recreation; industrial
process and cooling water; hydroelectric power
generation; navigation; unimpaired habitat for fish
and other aquatic life
C Drinking water (with treatment); fishing; primary 5.0 60 142b 94913
and secondary contact recreation; industrial
process and cooling water; hydroelectric power •
generation; navigation; habitat for fish and other
aquatic life
* From October 1 to May 14, the 7-day mean dissolved oxygen is not less than 9.5 mg/L, the 1-day minimum is 8 0 mq/L
May 15 to September 30.
In some cases, where desired uses of the water resource were being met, maintaining and protecting
these uses was set as an initial goal. For some brooks, aesthetics was the only use of concern; the
initial goal of meeting Class B standards was set even though the Class B standard also allows fishing
and swimming. For Jepson Brook, which is a channelized drainage ditch, meeting Class B standards
was not a priority. For No-Name Brook, there was a desire to upgrade the standard to Class B from
Class C. Thus, the variety of watersheds and water resources was reflected in the range of initial goals.
Assessment of Existing Data
An extensive effort was made to assess existing information and data, as described in a separate case
study at the end of Chapter 4. The following conclusions pertaining to the program's initial goals were
based on already available data:
• The city has an aggressive and extensive regulatory control system which addresses many NFS and
storm water control issues; with minor improvements, this system could fulfill the goals of maintaining
and protecting existing uses.
• Virtually no water quality data or information on any of the brooks in the city are available; more
information is needed to assess the existing conditions and establish goals for these systems.
• Extensive data exist on the Androscoggin River, which does not meet Class C standards; much of
the pollution appears to stem from upstream sources, but the contribution of CSOs needs to be
defined better.
27
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Future Activities
Several activities are planned for implementation. The data collection program (described in the separate
case study at the end of Chapter 4) will be CSO-related and implemented in 1993. Additional data
collection is being considered beyond that effort. After the initial planned data collection activities, the
initial program goals are to be reviewed and refined as needed. The city is also considering changes in
their current regulations to control urban runoff pollution better. Lewiston also plans to implement a
cross-connection removal program. In the long term, Lewiston's Clean Water Act master planning effort
plans to follow the overall planning approach outlined in this document, including data collection,
refinement of program goals, data assessment and modeling, ranking of problems, and BMP screening
and selection.
References
When an NT1S number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
COM. 1993. Camp Dresser & McKee. State of
California storm water best management practice
handbooks. California State Water Quality Control
Board.
SCVWD. 1990. Santa Clara Valley Water District. Santa
Clara Valley nonpoint source study—volume II: NPS
control program. San Jose, CA.
U.S. EPA. 1977. U.S. Environmental Protection Agency.
Urban stormwater management and technology:
update and users' guide. EPA/600/8-77/014 (NTIS
PB-275654).
U.S. EPA. 1987. U.S. Environmental Protection Agency.
Setting priorities: the key to nonpoint source control.
U.S. EPA Office of Water Regulations and Standards.
Washington, DC.
U.S. EPA. 1991 a. U.S. Environmental Protection
Agency. Developing the watershed plan. Published
in Seminar Publication: Nonpoint Source Watershed
Workshop. EPA/625/4-91/027 (NTIS PB92-137504).
Cincinnati, OH.
U.S. EPA. 1991 b. U.S. Environmental Protection
Agency. Developing goals for nonpoint source water
quality projects. Published in Seminar Publication:
Nonpoint Source Watershed Workshop. EPA/625/
4-91/027 (NTIS PB92-137504). Cincinnati, OH.
U.S. EPA. 1991c. U.S. Environmental Protection
Agency. Goals and objectives for nonpoint source
control projects in an urban watershed. Published in
Seminar Publication: Nonpoint Source Watershed
Workshop. EPA/625/4-91/027 (NTIS PB92-137504).
Cincinnati, OH.
Walesh, Stuart G. 1989. Urban surface water
management. New York: John Wiley & Sons, Inc.
28
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Chapter4
Determine Existing Conditions
Existing conditions must be investigated and described
prior to data collection, problem assessment, and BMP
evaluation. An investigation includes gathering, reviewing,
analyzing, and summarizing mapping resources,
hydrology, water quality and other environmental data,
as well as municipal planning information for the subject
region, county, municipality, or watershed. A description
of existing conditions has two major components:
• Watershed description, which characterizes the
sources of runoff and the "causes" of water resource
problems.
• Receiving-water description, which characterizes the
receptors of the watershed sources and their effects.
The watershed description defines the watershed area
and its subwatersheds and further identifies pertinent
geographic and environmental features (e.g., land use,
geology, topography, and wetlands), infrastructure
features (e;g., sewerage and drainage systems),
municipal data (e.g., population, zoning, regulations,
and ordinances), and potential pollution source data
(e.g., in-stream sediments, landfills, underground tanks,
and point source discharges). The receiving-water
description provides water resource information for
water bodies affected by the watershed, which can
include any type of receiving water (e.g., rivers,
streams, lakes, and estuaries) and its sediment and
biota as well as ground water.
This chapter describes an approach and rationale for
defining and assessing existing conditions. The
objectives are to develop a convenient way to organize
information, to develop a definition of existing conditions
pertinent to urban runoff pollution prevention arid
control, to identify data gaps to be addressed under a
field sampling program, and to maximize use of existing
available information. Extensive applicable information
usually is available from municipal government
departments, state and federal agencies, and private
vendors, as well as from files and data bases of maps
and environmental data. The more persistent and
thorough the investigator, the more information is
obtained. These early efforts support future phases of
planning by:
• Providing a basis for establishing and reassessing
water resource protection and improvement
objectives.
• Identifying pollutants of concern and related effects
on water resources.
• Providing a base map for locating pollution sources
and controls.
• Defining areas of concern where pollutant loadings
pose a high environmental or public health risk and
where source control efforts should be focused.
• Providing information for development of water
quality models, if needed.
• Planning, designing, and implementing BMPs.
• Evaluating post-implementation improvements and
beneficial use attainment.
• Identifying areas of good water quality and high value
to focus protection efforts.
This chapter first discusses how to prepare a watershed
description, including the types of information needed,
sources of watershed mapping and data, and methods
for organizing and presenting the information. For areas
where watershed mapping does not exist or needs to
be verified, techniques to develop mapping are
discussed. Next/the chapter describes developing a
receiving-water description including the types of water
resource data useful in investigating pollution sources
and assessing receiving water conditions, sources of
data, and methods for organizing and evaluating the
information.
Preparing a Watershed Description
The watershed is the entire surface area that drains into
a particular water body. Runoff from precipitation falling
on the watershed flows through systems of storm
sewers, channels, gullies, and streams to the lowest
elevation, usually to a river, lake, or estuary. Multiple
watersheds often exist in a study area because many
urban runoff pollution prevention and control programs
are based upon political boundary areas, such as the
limits of a municipality.
29
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The first step in describing each watershed is to
delineate the watershed and smaller watersheds or
subwatersheds within it, some of which might be
identified later in the planning process as significant
contributors to water resource impacts. Once the areas
are delineated, the municipalities and other entities with
jurisdiction for actions within them should be identified.
In many states, watershed delineation mapping is
available either on large base maps or through a digital
mapping resource. If mapping is not readily available,
however, watershed delineation can be done using
topographical maps; watersheds can be delineated by
connecting the points of highest elevation on land
surrounding the subject water body. Watershed maps
can be prepared using town or county topographic
maps, which are typically available at scales suitable for
use as a base map. These scales range from 1 in=200
ft for small watersheds, to 1 in=2,000 ft or higher for
large watersheds. The watershed map will serve as the
base map for additional data.
Types of Watershed Data
Table 4-1 outlines the types of mapping available for
preparing a watershed description and the pertinent
information in these sources. Land use data are
especially important to obtain given the relationship
between land use and urban runoff pollution (see
Chapter 1). Land use information can be separated into
either a few general categories or many specific
categories; an appropriate level of detail should be
selected before undertaking a mapping effort. Table 4-2
presents two options: 9 general categories of land use
and 37 specific categories. In addition to these options,
combinations of the two may also be considered.
Classifications should be selected based on the
diversity of land use types in the watershed and the
level of detail of existing information. They can also be
selected so that they are consistent with local zoning.
At a minimum, however, classification should include
major categories of land use, such as residential areas,
commercial and industrial developments, agricultural
operations, forested areas, open space and park land,
and other significant land uses that could affect water
resources.
Once the watersheds are delineated on a base map and
land use categories have been selected, additional
features and data for each watershed are compiled.
Pertinent information includes:
• Environment
- topography,
— land use,
— recreational areas (e.g., beaches, boating areas),
— soil and surface/bedrock geology,
Table 4-1. Use of Mapping Resources for Urban Runoff
Planning
Types of
Mapping
Use in Urban Runoff Planning
Drainage
basins
Topographical
Land use
Soil/geology
Vegetation
Zoning
Infrastructure
Assessor
maps
Aerial
photographs
Water bodies
Identify and delineate subwatersheds
Identify and delineate pollution sources
Delineate drainage areas, slopes, and
patterns
Calculate hydrologic model variables
Identify areas prone to erosion
Qualitatively analyze runoff quantity and
quality
Identify land use trends
Assess effects of land use on water quality
Locate potential sites for installation of control
structures
Evaluate erosion potential
Determine infiltration capacity for BMP design
Determine depth to bedrock
Identify depth to water table
Determine treatability of soil column
Identify areas protected by wetland regulations
Identify vegetative buffers
Identify undeveloped areas (e.g., forested
areas)
Identify priority areas based on type of
development
Identify potential areas of future development
Evaluate zoning changes and other
regulatory controls
Locate drainage system discharges
Design drainage system modifications
Identify opportunities for retrofit
Design storm water sampling program
Locate existing control practices
Locate utilities for placement of controls
Determine land ownership
Determine land use
Identify resource areas
Identify areas of erosion
Delineate potential problem areas
Identify pollutant transport considerations
— vegetation,
- natural resources (i.e., wetlands, wildlife resources,
and shellfish beds),
- temperature,
- precipitation, and
- hydrology.
Infrastructure
- roads and highways,
- storm drainage systems,
- sanitary sewer systems,
- treatment facilities, and
- other utilities (i.e., water, electric, gas).
30
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Table 4-2. Land Use and Land Cover Classification System
(Anderson, 1976)
Level I
Level II
1. Urban or 11. Residential
developed land 12. Commercial and services
13. Industrial
14. Transportation, communications, and utilities
15. Industrial and commercial complexes
16. Mixed urban or developed land
17. Other urban or developed land
2. Agricultural 21. Cropland and pasture
land 22. Orchards, groves, vineyards, nurseries, etc.
23. Confined feeding operations
24. Other agricultural land
3. Rangeland 31. Herbaceous rangeland
32. Shrub and brush rangeland
33. Mixed rangeland
4. Forest land 41. Deciduous forest land
42. Evergreen forest land
43. Mixed forest land
5. Water 51. Streams and canals
52. Lakes
53. Reservoirs
54. Bays and estuaries
6. Wetland 61. Forested wetlands
62. Nonforested wetlands
7. Barren land 71. Dry salt flats
72. Beaches
73. Sandy areas other than beaches
74. Bare exposed rock
75. Strip mines, quarries, and gravel pits
76. Transitional areas .
77. Mixed barren land
8. Tundra 81. Shrub and brush tundra
82. Herbaceous tundra
83. Bare-ground tundra
84. Wet tundra
85. Mixed tundra
9. Perennial 91. Perennial snowfields
snow or ice 92. Glaciers
• Municipality
— population,
- zoning,;
— land ownership,
— regulations,
- ordinances, and
- municipal source control BMPs (e.g., street
sweeping and catch basin cleaning).
Potential pollution sources/existing structural BMPs
- landfills,
- waste handling areas,
- salt storage facilities,
- vehicle maintenance areas,
- underground tanks,
- NPDES discharges,
— pollution control facilities,
- retention/detention ponds, and
— flood control structures.
Once these data are collected, some can be plotted on
the watershed base map if useful.
Sources of Watershed Mapping and Data
Watershed data are site specific and can be obtained
from municipal government departments, state and
federal agencies, and private vendors, and by searching
files and data bases of maps and environmental data.
Much of this information is contained in reports and
maps dealing with the watershed. At the federal and
state levels, mapping is increasingly available in digital
form that can be downloaded to a geographic
information system (GIS)—a flexible and powerful
computer-based tool that can store, display, and
analyze geographical information. Digital data for use
with a GIS are available from data bases maintained by
many state and federal agencies, and the private sector.
Two major sources of watershed data are U.S.
Geological Survey (USGS) maps and aerial
photographs. USGS maps depict many of the land
attributes shown in Table 4-2, including urban,
residential, forested, and wetland areas, as well as
roads, buildings, and water bodies. Aerial photographs
can provide a high level of detail on land use and also
can be used later in the assessment and ranking of
pollution sources. Aerial photographs are generally sold
as 9 in by 9 in prints that cover about half a square mile;
thus it may be necessary to overlap a number of
photographs to map an entire study area. Satellite
imagery is also available from several sources, but this
tool is more useful for a regionwide analysis and might
not provide the resolution required for analysis of
smaller watersheds. The following paragraphs
summarize sources of available watershed mapping
and GIS data.
Local
Existing watershed mapping is most readily available
from local municipal government departments that use
mapping to track property ownership, plan for future
development, maintain public utilities, and enforce
environmental regulations. Potential local sources of
mapping include the following municipal offices:
• Assessor: Maps of individual parcels, data on parcel
size and property ownership.
• Planner: Land use maps, aerial photographs, zoning
maps.
• Engineer: Storm sewer and other utility plans and
structural information.
• Public Works: Utilities and maintenance activities.
31
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• Conservation: Mapping of wetlands, soils, and other
vegetation and natural resources.
• Water Supply and distribution system utilities and
ownership of protected areas.
• Health: Septic system locations and maintenance
records, status of water resources with respect to
public use and consumption.
• Other: Watersheds and other information also might
be delineated on maps prepared for special drinking
water districts and flood control districts.
State
Watershed mapping might also be available from state
agencies responsible for conservation, water quality,
and oversight of state programs implemented at the
local level, such as wetland protection and health
codes. These maps, however, might not be as site
specific or as current as those available from local
sources and might be less accessible because of the
location or the structure of state government. One
method of locating mapping at the state level is to obtain
a directory of state departments and services and
contact those departments that would likely maintain
mapping. Generally the following types of information
are available:
• State environmental agency: Water quality data,
previous studies, existing controls, NPDES permits,
and compliance data.
• Conservation districts: Farm locations and
inventories, locations of existing agricultural BMPs,
soil descriptions.
• Water resources: Watershed delineations, locations
of potential pollution sources, status of water
courses, locations of public drinking water supplies.
• Wetlands and wildlife: Locations of protected
wetlands and other habitat areas.
• State colleges and universities: Mapping as part of
research, government contracts, or graduate
program studies at institutions with programs in
environmental engineering or science, civil or
agricultural engineering, or biology.
In addition, some states offer an extensive list of GIS
data. Data typically available from state GIS agencies
include: topography, state plane coordinates,
community boundaries, hydrography, major roads, land
use, major drainage basins and sub-basins, aquifers,
public water supplies, EPA-designated sole source
aquifers, surficial geology, census data, hypsography,
and protected open space. Each data type exists as a
separate "layer" of digital information. Many states
publish descriptions of available data layers and user
services.
Federal
The federal government collects and maintains
environmental mapping and data through a number of
programs and agencies. Readily available sources
include USGS Earth Science Information Centers! EPA
regions, and other agencies. Several federal sources of
mapping are listed in Table 4-3; some are national
offices of federal agencies that may direct inquiries to
satellite offices with data for specific regions. The
federal government also has an extensive amount of
GIS data available for use. Some of the more important
sources of these data are shown in Table 4-4. Additional
sources are available from EPA.
Table 4-3. Federal Sources of Watershed-Related Data
Source Type of Information
U.S. Geological Survey
National Cartographic
Information Center
507 National Center
Reston, VA 22092
U.S. Geological Survey
EROS Data Center
507 National Center
Reston, VA 22092
U.S. Department of
Agriculture
Soil Conservation Service
(Contact the office of SCS
State Conservationist or the
State Agricultural Experiment
Station)
Hazardous Substance Sites
National Technical
Information Service
Computer Product Support
Group
5285 Port Royal Road
Springfield, VA 22161
U.S. Fish and Wildlife Service
(Contact:
National Cartographic
Information' Center
P.O. Box 6567
Fort Worth, TX 76115)
Mapping of topographic features,
land use, land cover, and slopes;
aerial photographs; and satellite
imagery
High altitude aerial photography
Soil survey reports that include
soil maps, soil descriptions, aerial
photographs, and soil
management information
including erosion potential,
suitability for septic tank
adsorption fields, and flooding
frequency
Topography, soil types, soil
conditions, and substance
storage data for specific studied ,
sites
Wetland mapping on USGS
topographical quadrangles
Private
Numerous private firms produce mapping, GIS data,
aerial photographs, and land surveys, frequently for
municipal clients. Local firms involved in mapping and
GIS data are listed in the yellow pages or local business
directory. An extensive list of private GIS data sources
and services can be obtained from private sources,
such as trade journals. In addition, private colleges and
universities with programs in geology, engineering, or
environmental protection can be valuable sources.
32
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Table 4-4. Federal Sources of Geographic Information
System Mapping Data
Source
Type of Information
U.S. Geological Survey
Room 1C402
507 National Center
Reston, VA 22092
U.S. Bureau of Census
Data User Services Division
Room 407
Washington Plaza
Washington, DC 20233
U.S. Fish & Wildlife Service
• National Wetlands Inventory
9720 Executive Center Drive
St. Petersburg, FL 33702
U.S. Soil Conservation Service
National Cartographic Center
P.O. Box 6567
Fort Worth, TX 76115
Digital elevation models
(OEMs)—digital terrain elevations
at regularly spaced horizontal
intervals
Geographic names information
system (GNIS)—proper names of
places, features, and areas
Planimetric data in digital line
graph (DLG) form including
boundaries of states, counties,
and cities; transportation facilities
including roads, trails; pipelines
and transmission lines;
hydrography including streams
and water bodies; and
topographical contours
Land use and land cover (LULC)
data on urban or developed land,
agricultural land, rangeland,
forested land, water, wetlands,
barren land, tundra, and
perennial snow and ice
Digital political and census data
such as roads, rivers, political
boundaries, address ranges, and
zip codes
Vegetated wetland and
deep-water habitat mapping
Soils information (address shown
is for the federal SCS office; soils
information can also be obtained
from individual state offices) :
Analysis of Watershed Data
This section discusses several methods of analyzing
watershed data to define existing conditions. These
methods include development and use of watershed
maps and analysis of existing regulatory and municipal
practices and other existing BMPs.
Development of Watershed Maps
Maps are created to show watershed-related data, such
as topography, land use, watersheds and subdrainage
areas, soils, infrastructure, natural resources,
recreational areas, special fish and wildlife habitat
areas, and existing pollution control structures. All this
information is important in urban runoff pollution
prevention and control planning. If maps are generated
from information that is several years old, field
investigations might need to be conducted to verify and
update the information. The most efficient way to verify
this information is through a "windshield survey." In
urban and suburban areas, most watershed areas are
accessible by car. Field observations are compared with
existing maps, and changes or additions are traced onto
the base map.
When required information is not available from the
sources discussed in the previous section, a more
complete survey of the watershed will be required. In
small watersheds of a few acres, these surveys are
typically conducted by car and on foot. To conduct a
survey of a large watershed, however, aerial
photographs can supplement the site investigations and
provide a more complete picture.
Another method of generating watershed maps is by
computer. The data in a GIS are organized into thematic
layers (such as land use, water bodies, watersheds,
topography, or transportation) which can be overlaid
and plotted in any combination. In addition, GIS
systems are equipped with a data management system
that can organize and store text and numerical
descriptive information. This information can be very
basic, such as whether a land use in a particular area
is residential or industrial, or it can be very
sophisticated, consisting of multiple tables of data,
including land ownership information, discharge
monitoring report information, soils information, or water
quality information. Given the technical expertise
required and the capital expenditures for computer
hardware and software, the use of a GIS might not be
feasible for some urban runoff pollution prevention and
control program teams. A GIS requires an appropriate
personal or mainframe computer and a graphics plotter.
Developing new mapping for an area, whether using
GIS, aerial survey, or other means, can be expensive
and time consuming. The urban runoff planning effort
should not turn into a mapping and GIS effort. Since
base mapping and GIS tools have numerous uses
within a community, development of such a system
should be considered as a separate program.
Use of Watershed Maps
Once watershed maps have been developed, additional
data can be obtained by measuring the area of the
watershed and its subwatersheds—useful information
for calculating runoff flows and pollutant loads from the
watershed. Available methods for measuring area range
from manually measuring to using an electronic digitizer
to using GIS software. In one method, a grid overlay is
created on the watershed base map of known
dimensions and the area is approximated by counting
the grid squares in the watershed. Another similar
method is to use a planimeter, a device designed to
trace the watershed boundary. To use a digitizer, which
functions as a computerized planimeter, the map is
placed on a surface underlaid by an electronic grid
system. The boundary of the watershed is traced with
an electronic pointer which digitally records the
coordinates, and the area is then calculated by
33
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computer. In addition, GIS software has algorithms that
can be used to measure area.
Once the watersheds and subwatersheds are
delineated and the existing conditions are indicated, the
total area of each land use category for the entire
watershed and each subwatershed can be calculated.
This calculation is important because each type of land
use tends to have its own pollutant loads and urban
runoff pollution prevention and control issues. After the
runoff from each type of land use is characterized,
future changes in pollutant loading due to planned
changes in land use can be estimated and used to
assess potential future impacts and control scenarios.
These data will be important to the problem assessment
and ranking process described in Chapter 6.
Other land use analyses can be conducted by mapping
and reviewing different watershed attributes. These
analyses can be facilitated by creating overlays
depicting individual watershed attributes or by
displaying selected thematic layers on a GIS. For
example, historical land use changes can be assessed
by comparing historical mapping from USGS
topographical maps, which are based on aerial
photography and periodically updated, thus documenting
land use changes over time. In many urban areas, the
USGS maps exist from as early as the 1880s. Recent
changes in land use can be used to focus source control
efforts, to locate new sampling stations, or to modify
land use regulations.
Analysis of Regulatory and Municipal Practices
Analyses of other types of watershed data generally
consist of creating tabular summaries, plots and figures,
or maps designed to describe the major characteristics
of each data type and subtype. Public works,
engineering, planning, and health department
personnel can assist in developing a profile of existing
regulations and practices. Table 4-5 is a simple format
for presenting existing municipal practices; the
information in this table is very general, indicating only
whether or not certain practices are used. The
comparison also can be more detailed as shown in
Table 4-6, which describes the actual characteristics of
each practice, such as the equipment used and
frequency of actions.
In addition to these municipal practices, regulatory
control practices affecting urban runoff pollution should
be investigated and summarized. Table 4-7 outlines an
example review of local subdivision regulations that
could be used to prevent and reduce urban runoff
pollution in four communities. The table analyzes the
regulations' ability to provide runoff quantity control,
solids control, and other pollution control. Such a review
can be developed for all regulations (e.g., zoning,
wetlands, earth removal, and special protection districts)
Table 4-5. Use of Nonstructural Practices in Study Area
Watersheds (Adapted from Woodward-Clyde
Consultants, 1989)
Control Watershed
Practices 1
Street sweeping
Litter control
Public education
Pet waste
removal
Local ordinances
Fertilizer control
Reduced
sanding and
salting
Catch basin
cleaning
Hazardous
waste collection
days
Yes
Yes
Yes
No
Yes
No
Yes
Yes ,
Yes
Watershed
2
Yes
Yes
No
No
No
Yes
Yes
No
Yes
Watershed
3
No
Yes
No
Yes
Yes
Yes
No
Yes
No
Watershed
4
Yes
Yes
No
Yes
Yes
Yes
Yes
Yes
No
Yes = Control measure exists
No = Control measure does not exist
that could affect urban runoff pollution. Generally, the
municipality should investigate all aspects of current
practices that could affect storm water runoff quality,
including the practices and regulations shown in Tables
4-5, 4-6, and 4-7, as well as others: special
requirements for stream corridor preservation, buffer
zones, and open space preservation; septic system
planning and testing requirements; and regulations
pertaining to nontidal wetlands. These issues are
discussed further in the regulatory control section of
Chapter 7. An example analysis of both regulatory and
municipal urban runoff practices is provided in two case
studies at the end of this chapter.
Contents of a Watershed Description
Once the information on existing conditions has been
gathered and the watershed maps have been
developed, the watershed can be described. The
watershed description is organized by data type (i.e.,
environmental, infrastructure, municipal, and potential
sources/existing BMPs). Each data type has its own
section with a narrative description of each data subtype
supported by appropriate tables and/or maps. The
maps and data developed in the previous steps provide
the primary information in the description. While not all
this information will be of immediate use to the program
team at this stage, it could be important as planning
continues.
Information gaps should be outlined and presented in
the watershed description as a first step in developing
a plan to gather additional information (see Chapter 5).
A summary listing of information recommended for the
34
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Table 4-6. Frequency and Types of Nonstructural Practices Used in Study Area Watersheds (U.S.
Community 1 Community 2 Community 3
EPA, 1992)
Community 4
Street Sweeping
Frequency
Equipment (number)
Catch Basin Cleaning
Frequency
Equipment (number)
Solid Waste Management
Every other day on 30
major streets and once
a week on others
Mechanical (3)
Once a year
Mechanical (1): Clamp
Once a week downtown
and once a year in
other areas
Mechanical (1)
Vacuum (3)
Once a year
Mechanical (1):
Orange Peel
Twice a year
Mechanical (1)
Twice a year
Mechanical (1)
Roadway Sanding and Salting
Sand:salt ratio 4:3
Salt used (tons/road mile) 11
Special reduced-use zones None
Other Nonstructural Practices
Fertilizer and pesticide usage None used
Animal waste removal
Illicit connection
identification and removal
No program
No program
1:1
12
None
Fertilizer used on town
ball fields
No program
No program
4:1
3.5
None
None used
No program
No program
Once a year, except
Lake Cochichewick
(three times a year) and
downtown (twice a year)
Mechanical (2)
Once a year
Mechanical (1): Orange
Peel
ntjsiuenuai
Commercial
Recycling program
Once a week
Twice a week
Paper
Fall leaves
Once a week
Private collection
Paper
Once a week
Twice a week
None
Once a week
Once a week
Paper
Leaves/grass
7:1
6
None
Granular fertilizer used
for sodding
No program
No program
watershed description is provided later in this chapter,
and two examples are given in the case studies at the
end of the chapter.
Preparing a Receiving-Water Description
In addition to a watershed description, a receiving-water
description should be prepared, which includes the
types of water resource data that should be sought,
sources of data, and methods to summarize and
analyze existing receiving-water conditions. Many
program areas have multiple receiving waters, such as
tributaries, larger rivers or estuaries, or lakes; in many
cases, adding ground water to this list could be useful.
Effective identification and use of existing water
resources data could reduce the program schedule and
cost, most significantly by reducing additional sampling
and analysis. In addition, review of historical water
quality data provides a basis for:
• Establishing and reassessing goals.
• Documenting the type and extent
runoff-related water resource impacts.
of urban
• Identifying data gaps that should be addressed with
a sampling program.
• Identifying priority areas and major nonpoint pollution
sources.
• Quantifying pollutant loads.
• Documenting impairment or loss of beneficial uses
and water quality standard violations.
• Documenting areas with good water quality that could
be threatened or that should be protected.
Types of Receiving-Water Data
The types of water resources data that should be sought
include:
• Source input data (flow and quality)
- CSO data,
- storm water data, and
- other NFS data.
• Physical/hydrologic
- physiographic and bathymetric data,
35
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Table 4-7. Existing Regulatory Control Summary—Subdivision Control (U.S. EPA, 1992)
Subdivision Control Community 1 Community 2 Community 3
Community 4
Scops of regulations
Runoff Quantity Control
Opon space
Postdavelopment
flow control
Runoff recharge
Additional Controls
Solids control
Other pollution control
AH lots being
subdivided come under
Subdivision
Regulations; lots on an
accepted public way
and with sufficient
frontage are classified
as "Approval Not
Required"
Requires due regard for
maintaining natural
features and open space
None specified
None specified
None specified
None specified
All lots being
subdivided come under
Subdivision
Regulations; lots on an
accepted public way
and with sufficient
frontage are classified
as "Approval Not
Required"
Requires that efforts be
made to maintain
natural features and
open space
Requires calculations
showing no increase in
peak flow during 100-
year storm
None specified
Requires the
development of a runoff
control plan that
minimizes erosion
None specified
All lots being
subdivided come under
Subdivision
Regulations; lots on an
accepted public way
and with sufficient
frontage are classified
as "Approval Not
Required"
Requires that efforts be
made to maintain
natural features and
open space
None specified
None specified
None specified
None specified
All lots being
subdivided come under
Subdivision
Regulations; lots on an
accepted public way
and with sufficient
frontage are classified
as "Approval Not
Required"
Requires that efforts be
made to maintain
natural features and
open space
Requires calculations
showing pre- and
postconstruction peak
flows and total volumes
for 2-, 10-, and
100-year storms
Requires that storm
water be recharged
rather than piped to
surface waters to the
maximum extent feasible
Requires that an
erosion control plan be
developed for during
and after construction
None specified
— flow characteristics,
— tidal elevation in coastal areas, and
- sediment data.
• Chemical
- water quality data and
— sediment data.
• Biological
- fisheries data,
- benthos data,
— plankton data, and
— biomonitoring data.
• Water quality standards and criteria
— federal criteria and
— state standards.
These data should be gathered to help the program
team develop a profile of the conditions in the water
body of concern. Source discharge, water, sediment,
and biological data typically will exist from past studies
of the watershed. By gathering this information, a
picture can be developed of existing conditions and data
gaps can be identified.
Sources of Water Resources Data
A wide range of sources of existing water resources
data can be found at the local, state, and federal levels.
Each agency that has conducted water resource
assessments in the study area should be contacted for
its available data and asked about other potential
sources. As this chain continues, fewer new sources are
identified; diminishing returns indicate when most, if not
all, available data have been obtained. The following
paragraphs summarize potential, as well as established,
sources of water resources data.
Local
Many municipal departments listed earlier as potential
sources of mapping can also provide water resources
data from previous studies, wetland or other permit
applications, or routine water resources monitoring. For
example, health departments typically conduct routine
monitoring of water resources to protect the environment,
to ensure the safety of recreational swimming areas,
and to manage onsite sewage disposal systems or
septic tanks. Municipal departments responsible for
reviewing construction and wetlands permit applications
can track local water quality conditions as part of local
36
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water resource regulations designed to prevent
cumulative degradation of sensitive resources. Local
permit applications can contain recent and historical
water quality, source discharge, and hydrologic data to
demonstrate compliance with local or state wetlands
and water quality regulations. Receiving-water data also
might be available from NPDES monitoring records,
which often represent valuable information about the
effects of a specific pollution source. Also data might be
available for water bodies in special drinking-water or
flood-control districts.
State
In most states, several agencies deal directly or
indirectly with water quality issues, such as water
resources, pollution control, clean lakes, transportation,
fisheries, environmental review, wetlands, and coastal
zone management. The agencies might also deal with
water quality in terms of discharge permit applications,
fisheries status reports, development review, wetlands
impacts, and effects on coastal resources. Every 2
years, states prepare two reports—a Section 305(b)
Water Quality Assessment Report, summarizing the
status of the states' waterways, and a Section 319
Nonpoint Source Assessment Report, listing water
bodies affected by nonpoint sources—that indicate
sources of existing water data, programs that address
NFS pollution, and sources of agency assistance.
These reports are available from the state water
pollution control agency or the EPA regional office.
Information concerning water bodies in the Clean Lakes
Program (CWA Section 314) also might be available
from the state.
Federal
The federal government is an excellent source of
hydrology and water resources data through agencies
such as EPA, SCS, and the USGS. Table 4-8 outlines
a number of major federal government sources of water
resource data including water quality, hydrology,
meteorology, biomonitoring, and sediment quality data.
In some cases, information can be supplied through the
mail; in other cases, such as the USGS National Water
Data Exchange, the information can be accessed only
by using a computer modem.
Analyzing Water Resources Data
Existing data collected by different local, state, and
federal organizations likely were collected using
different methods, at different times, and with different
objectives. Each data set should, therefore, be reviewed
to assess its quality and applicability to urban runoff
pollution prevention and control program efforts.
Although the criteria for this assessment should be site
specific, basic considerations include sampling program
Table 4-8. Federal Sources of Water Resource and
Hydrology Data
Source
Type of Information
U.S. Environmental Protection Agency
Clean Lakes
Program
National Estuaries
Program
Mussel Watch
Program
Ocean Data
Evaluation System
Permit Compliance
System (PCS)
STORET Data
U.S. Geological Survey
Water Resources
Division
Water Quality Branch
Water quality and other diagnostic
information for lakes monitored under
the Clean Lakes Program
Water quality and other diagnostic and
research data for 21 coastal
embayments
Monitoring of mussel tissue for heavy
metals and other toxic and xenobiotio
compounds in areas of wastewater
discharges
Pollution sources, effluent, water
quality, biological and sediment
pollution data
Point source discharge data from
NPDES monitoring programs
Flow and water quality data in receiving
waters
Flow and water quality data collected at
USGS streamflow gaging stations for
rivers and streams
Receiving waterflow and water quality
data, point source data from NPDES
monitoring programs
U.S, Department of Commerce
National Climatic Precipitation data and statistics from
Center weather-monitoring stations nationwide
U.S. Food and Drug Administration
Shellfish Sanitation
Branch
Sanitary survey reports for coastal
areas with shellfish habitat. Reports
include shoreline surveys for actual
potential pollution sources and water
sampling data for total and fecal
coliform
U.S. Army Corps of Engineers
Reservoir water
Dredging Permit
Application
Program
Other
U.S. Department of
Agriculture, Soil
Conservation Service
National Oceanic and
Atmospheric
Administration
Federal Emergency
Management Agency
Quantity and quality data
Water and sediment quality data
collected in support of Clean Water Act
Section 404 dredge and fill permit
applications
Sediment data for specific structural
controls
Marine charts for coastal areas, tide
tables, and tidal current tables
100-year flood plain elevations
design and quality assurance/quality control (QA/QC).
Data that would be useful in the planning process can
be entered into a data base to facilitate data
organization, management, and analysis. One method
is to enter the information into a personal computer-
37
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based standardized spreadsheet format that allows
sorting and plotting of the data. Spreadsheets are
extremely versatile and allow the user to:
* Organize data from multiple sources.
• Analyze data from individual sampling programs or
of aggregate data.
• Sort data, such as by sampling station location,
analytical parameter, or date of collection.
• Statistically analyze data.
• Create x-y plots of parameter concentration versus
time or distance.
* Continuously update the data base.
Table 4-9 presents an example spreadsheet format with
the results of example statistical calculations. Figure 4-1
illustrates an x-y plot of total suspended solids (TSS)
concentrations over time at the monitoring station
used in Table 4-9. More advanced applications of
spreadsheets can be used for hydrologic calculations
and for calculating pollutant loading based on runoff
volumes and pollutant concentrations. Spreadsheets
can also be used to create data input files for computer
models that help evaluate pollutant concentrations in
receiving waters and effects on water resources and
beneficial uses.
In addition to simple spreadsheet programs for storing
and organizing data, specialized database management
programs can be utilized. These programs are designed
specifically for organizing large amounts of data and
manipulating the data to produce customized reports.
These programs can often produce output for direct use
in analysis programs, such as those discussed in
Chapter 6. Also, since GIS applications generally use
data bases to store and retrieve data for generating data
layers, a GIS system could be used for analyzing the
existing water resources data. In this way, the water
resources information can be directly plotted on the
base maps generated during the watershed description
Table 4-9. Example Water Resource Data Spreadsheet
Station"
45
45
45
45
45
45
45
45
45
45
45
45
45
45
45
Date"
031885
032085
040185
042985
050385
051385
051585
052085
052985
062585
071785
072385
072685
072785
073185
Day0
108
110
122
150
154
164
166
171
180
207
229
235
238
239
243
Timed
0800
1310
1010
1300
1230
1410
2010
1800
1330
0810
2040
0850
1330
1620
1150
Parameter9
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
TSS
Avg
Dev
Max
Min
Concentration,'
mg/L
50
30
800
330
200
20
50
100
40
400
324
930
160
120
450
266.93
272.08
930
20
Flow,9
tfVs
2.1
2
10.5
4.1
2.6
2.3
1.9
3
2.7
2.9
4.3
6.1
2.5
2.9
3.7
Agencyh
uses
EPA
EPA
uses
EPA
EPA
EPA
USGS
EPA
USGS
EPA
EPA
USGS
EPA
USGS
Method1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
*Tha station number assigned to the collection location during the study; the same physical location may have more than one station number
for surveys conducted by different agencies.
Date of the sample collection.
0 Sequential numbering of days starting with the earliest date of data collection.
dTima of the sample collection (HHMM).
"Water quality parameter (TSS = total suspended solids).
1 Mass of constituent per unit volume.
° Volume per unit time during sampling.
. Agency conducting the survey.
1 Analytical method (1 = Standard Method 2540 D).
38
-------
Station Number 45
1
0.9
0.8
^ 0.7
^1
if 0.6
g| 0.5
0.4
0.3
O.Z
0.1
0
I
100 120 140 160 180 200 220 240 260
Day Number
Figure 4-1. Total suspended solids (TSS) concentrations.
process, which allows the user to link watershed
information, such as land use or soil conditions, directly
with water resource data.
The Data Management and Analysis section of Chapter
5 discusses in more detail presenting and analyzing
water resource data.
Contents of a Receiving-Water Description
After the water resource data have been gathered, a
receiving-water description must be developed to
describe the existing conditions of the water body being
investigated. This description should include summaries
of the data collected, organized by data type (i.e.,
physical/hydrologic, chemical, biological, and water
quality standards and criteria). Each summary includes
a narrative description outlining the information
gathered for each data type. This information should be
presented in a way that indicates existing data gaps and
a priority for addressing those gaps.
Summary
This chapter discusses the collection of existing
information to describe the planning area's watersheds
and water resources. The information collected should
concentrate on the delineation of watersheds; the
description of land uses in the watersheds; and the
identification of related environmental, infrastructure,
municipal, and pollution source data. The water
resource description should present data on physical,
chemical, and biological conditions of the water body
along with applicable standards and criteria. Based on
the material presented in this chapter, a suggested
outline for the existing conditions description is as
follows:
• Project area
• Watershed data description
- environmental data,
- infrastructure data,
- municipal data,
- potential sources/existing BMP data,
- miscellaneous data, and
- data gaps.
• Receiving water data description
- source input data,
- physical/hydrologic data,
— chemical data,
- biological data,
- water quality standards and criteria,
- miscellaneous data, and
- data gaps.
• Summary of data needs
• Refinement of goals
Expending resources at the beginning of the planning
process "to locate as mucfi e^isHng~Tn"formation as
possible is cost effective in the long term, because it
helps maximize use of existing information, minimize
data collection costs, and avoid overlooking important
data resources.
The information, having been gathered and analyzed,
has to be examined to determine existing knowledge
gaps. If necessary information is unavailable, the
program team must collect additional data. The next
chapter discusses obtaining and analyzing the water
resource data required to describe existing conditions
fully.
The program team can base site-specific program goals
on the existing conditions information by examining the
general initial goals and refining them. As discussed in
Chapter 3, a knowledge of existing conditions is
important to have before site-specific goals can be
established.
The following case studies provide examples of existing
conditions assessment for water bodies in Lewiston,
Maine, and Pipers Creek in Seattle, Washington.
39
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Case Study:
City of Lewiston, Maine,
CSO, Storm Water, and NFS Planning Program
Existing Conditions Assessment
Background
Lewiston, Maine, embarked on a planning program in 1991 to address CSO, storm water, and NPS
pollution issues. Overall aspects of this planning program are described in a companion case study at
the end of Chapter 3. This presentation focuses on the city's efforts to evaluate existing conditions.
The city invested significant time and energy in assembling and analyzing existing information in an effort
to maximize the use of existing data and minimize the need for new data (and the potentially high cost
of collecting it). The city also wanted a systematic way to sort and analyze information with respect to
the critical pollution control issues. A set of "baseline information" was also desired from which to compare
and assess future program needs and activities.
Existing conditions were assessed using a methodology similar to that described in Chapter 4. A
watershed description, a receiving-water description, and a summary of data needs were prepared. Each
of these components, including the approach and results, is described below.
Watershed Data
The program team, using the list of watershed data in Chapter 4, contacted and held meetings with
individuals who might have pertinent data. The list of data compiled is shown in Table 4-10.
Environmental data on the watersheds were generally available from a combination of local, state, and
federal sources, as shown. Infrastructure data were available from the city, who already had accurate
mapping of the major roadways, drainage system, and sewerage system. Municipal data, as well as
data on potential pollution sources and BMPs, were available but required significant effort to compile.
Areas requiring a lot of work—potential pollution sources, nonstructural controls, municipal source
controls, and existing structural controls—are described in the following paragraphs.
Potential Pollution Sources
While a number of possible pollution- sources existed within the city's watersheds, they had never been
mapped. The city compiled extensive information on underground and aboveground storage tanks,
landfills, vehicle maintenance areas, salt storage and snow dumping areas, CSOs, and storm drain
cross-connections. These were plotted on a base map, along with watershed boundaries, receiving
waters, and other important features such as gaging stations, recreational areas, and flood control
structures. The map contains information similar to that required in the NPDES storm water permit
regulations. It provided a convenient way of reviewing watersheds and potential pollution sources within
them, possible threats to receiving waters, and the underlying zoning districts.
Most of the potential pollution sources exist within the watershed areas of Jepson Brook, Hart Brook,
and Androscoggin River—the most developed watersheds. Stetson Brook watershed has several
potential sources, and Salmon/Moody Brook has almost none. No-Name Brook and Pond watersheds
did not have many source areas. One area of medium-density residential development on Sabattus
Street with a concentration of underground tanks was noted. Located at the brook's downstream portion
near the pond, this area is of concern.
Nonstructural Controls
The city's land use and zoning code and other development guides were reviewed to determine the
status of nonstructural controls. The city was determined to have a comprehensive set of nonstructural
40
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Table 4-10. Lewiston Watershed Data
Description Source
Environmental
Topography
Land use
Recreational areas
Soil and surface/bedrock geology
Vegetation
Natural resources
Temperature
Precipitation
Hydrology
Infrastructure
Roads and highways
Storm drainage system
Sanitary sewer (and combined
sewer) system
Treatment facilities
Other utilities
Municipal
Population
Zoning
Land ownership
Regulations and ordinances
Municipal source control BMPs
Potential Sources/BMPs
Landfills
Waste handling areas
Salt storage facilities
Vehicle maintenance facilities
Underground tanks
NPDES discharges
Pollution control facilities
Retention/detention ponds
Flood control structures
USGS topographical maps; city's 100- and 200-scale maps
Zoning Map Lewiston, Maine, revised 11/7/91; Comprehensive Land Use Plan (1987)
Parks Department inventory
USDA Soil Conservation Service Soil Survey
USGS quadrangle sheets and Maine DOT aerial photos
Comprehensive Land Use Plan (1987)
NOAA
National Climatic Data Center; four rainfall gauges owned and operated by Lewiston
FEMA flood mapping
Various city maps exist
Record drawings provided by the city
Record drawings provided by the city
Record drawings provided by the city
Gas, New England Telephone maps
U.S. Census data; Maine Dept. of Data Research and Vital Statistics; Comprehensive
Land Use Plan (1987)
Zoning regulations; city zoning map; Comprehensive Land Use Plan (1987)
City Assessor's maps
Draft development permit provided by the city; Comprehensive Land Use Plan (1987)
Interviews with various city departments and staff
Locations developed by city
Locations developed by city
Locations developed by city
Locations developed by city
ME DEP list supplemented by the city
Locations developed by city
Lewiston Area Water Pollution Control Authority
Public Works Department inventory
Public Works Department inventory
41
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controls, which were analyzed and presented in a series of matrices—a convenient tool to assess the
strengths and weaknesses of the regulations.
The major areas of existing regulatory authority include conservation districts, performance standards,
and development review standards. Conservation districts (Table 4-11) are areas in the city that require
special protection. Each district has requirements on the amount of open space or impervious surface
area, on the size of buffer zones where applicable, and for solids control and pollution control.
Performance standards (Table 4-12) are designed to control impacts of certain activities (e.g., earth
removal or timber harvesting) in specific areas (e.g., shoreline or flood plains). In each case, buffer or
filter strips are required as appropriate. Controls also are specified in most cases for solids or other
potential pollutants.
Development review standards (Table 4-13) apply to all new developments above certain specified sizes.
The sizes are relatively small so that most new developments or redevelopments are Covered. These
standards contain a number of general review criteria for storm water management, erosion control, and
other miscellaneous items.
Overall, the controls provide a more thorough and aggressive program than many communities of similar
size have. The major area needing strengthening was the control of postdevelopment flows. Most
requirements involved control of a 25-year storm which is oriented toward flood control. Because smaller
storm events (i.e., 1-year return period or less) typically contribute most of the urban runoff pollutant
Table 4-11. Summary of Lewlston Nonstructural Controls—Conservation Districts
Resource Conservation
(RC)
Ground-Water
Conservation (GC)
Lake Conservation (LC)
Scope of regulations
Runoff Quantity Control
Open space
Postdevelopment flow control
Runoff recharge
Additional Controls
Solfds control
Other pollution control
Protects fragile ecosystems Protects existing and
and areas of unique value potential ground-water
as shown on city zoning map supply areas
At least 90% open space
Minimum 25-ft stream buffer
Minimum 50-ft shoreline
buffer
None specified
None specified
Earth removal performance
standards apply (see Table
4-12)
Performance standards
apply (see Table 4-12)
Maximum impervious surface
ratio of 0.25
None specified
Specify measures to protect
from loss of recharge
No earth removal below
seasonal high ground-water
table
Prohibits solid waste
disposal, petroleum storage,
deicing chemical storage,
snow dumping, hazardous
waste storage, automotive
repair shops, junkyards,
cemeteries, and land
application of sewage
Ground-water protection plan
required
Protects water quality of
No-Name Lake
Maximum impervious surface
ratio of 0.1
Minimum 50-ft shoreline
buffer
Increase of <20% for
25-yr/24-h storm
None specified
Submit erosion and
sediment control plan to
minimize sediment discharge
to pond
Prohibits use of fertilizers
within buffers, onsite sewage
disposal within 250 ft
Total lawn and garden area
<30% of lot area
No increase of phosphorus
in pond >one part per billion
for a development
42
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Table 4-12. Summary of Lewiston Nonstructural Controls— Performance Standards
Shoreline Area Earth Removal Timber Harvesting
Scope of
regulations
All areas within 250' ft of
Androscoggin River and
tributaries and all areas in.
Resource Conservation
District (see Table 4-11)
New earth removal or
expansion of existing
activities
Limits activities
depending on zoning
district
Floodplain
Management
Controls
development within
floodplains
Runoff Quantity Control
Open space 75-ft buffer around Natural vegetative strip at
i high-value wetlands least 50 ft wide must be
maintained around activity
Filter strip of varying width (can be as High as 100 ft)
•" required between road
and water body
Postdeyelopment
flow control
Runoff'recharge
Road culverts and. bridges No net increase in runoff
shall pass 25-yr storm discharge
None specified None specified
Minimum 50-ft stream
buffer
Buffer strip required
depending on slope
Limits on amount of
vegetation removed
depending on area
None specified
None specified
Additional Controls
Solids control No grading or filling on
'. slopes >25%
All listed activities must
prevent erosion and
sedimentation • ' '•
Other pollution
control
Filter strip required near
tilled land
Subsurface .disposal not,
allowed within 100 ft of
water body
Agriculture shall minimize
bacteria and nutrient
contamination
No slopes greater than 2:1 None specified
Erosion prevention plans
including the use of ditches,
sedimentation basins, or
dikes must be used if the
activities are within 250 ft of
a water body
Operation may not cause
harmful leachate
Petroleum or hazardous
waste storage prohibited
Prohibited in resource
conservation district
Limited in shoreline
areas and lake
conservation district
None specified
None specified
None specified
Structures must be
protected from flood-
waters (limits
erosion)
Locate sewerage
system to minimize
contamination of
waters
loading on a long-term basis, control of such smaller storm events was recommended. Another area that
could be strengthened is the onsite disposal of storm water. While noted in the development review
standards, this plan could be made more specific. Finally, other parts of the development review
standards could be made more specific with respect to runoff pollution control.
Municipal Source Controls
Interviews were conducted to summarize the current city "source control" activities (summarized in Table
4-14). Most activities conducted by the city appeared reasonable with respect to standard practices of
similar sized municipalities. Areas that appear to need further consideration include cross-connection
removal•, road salting, and household hazardous waste pickup. The city has identified some
cross-connections and plans to implement a removal program. Road-salting policy does not vary in
sensitive areas such as No-Name Pond; such a policy could be beneficial in the sensitive receiving
waters. Many communities are involved in household hazardous waste pickup programs. Such a program
could prove beneficial and would be consistent with the city's other aggressive solid waste programs.
Such programs, however, also can be expensive. Further evaluation of municipal BMP/source control
activities is planned after collection of data and evaluation of various possible BMP programs.
43
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Table 4-13. Summary of Lowlston Nonstructural Controls—Development Review Standards
Storm Water Management Erosion Control Other
Scope of Standards apply to all new subdivisions, residential developments with more than five units,
regulations nonresldential developments, and numerous other development categories.
Runoff Quantity Control
Open space Preserve natural drainage ways Preserve natural vegetation
No fill storage within 50 ft of
water body
Postdevelopment Must handle 25-yr storm without None specified
flow control surcharge
Runoff recharge Dispose of storm water on the None specified
property to the extent possible
Landscaping plan required
Open space set-asides for larger
developments
Storm water drainage plan required
(25-yr/24-h storm)
None specified
Additional Controls
Solids control None specified
Earth material removal Erosion control plan required
standards apply (see Table 4-12)
Permanent erosion control
measures within 15 days after
final grading, or use temporary
measures
Use debris basins, silt traps, or
other measures during
construction
Othor pollution Cannot degrade biological and None specified
control chemical properties of receiving
waters; such controls as oil and
grease traps, onsite vegetated
waterways, and reductions of
dofcing and fertilizers may be
required
Avoid extensive grading and filling
No adverse impact on ground-water
quantity or quality
No undue water pollution
No adverse impact on shoreland
Existing Structural Controls
The structural controls installed in the city within the last few years were inventoried. The information
compiled is summarized in Table 4-15. Few structural controls exist largely because of the limited new
development or redevelopment in recent years. Most of the projects used the 25-year storm required in
current city regulations as the design criteria. As noted in the nonstructural control discussion, inclusion
of smaller events is being considered as an additional requirement.
Most structural controls listed are detention ponds. In one case, subsurface infiltration is used. In another
case, an inlet structure controls flow from the Garcelon bog wetland into Jepson Brook, and thus is not
a development-related project. The summary indicates that there is currently no inspection or
maintenance schedule for most of the facilities—a shortcoming for the flood-control use of the facilities
as well as if the facilities were to be used to assist in urban runoff pollution control.
Receiving-Water Data
As shown in Table 4-16, data on receiving waters or on the major pollution sources to the receiving
waters were limited. Data were available only for the Androscoggin and Little Androscoggin (which feeds
into the Androscoggin River in Lewiston) rivers. The USGS maintains monitoring stations on both rivers,
and published data are available on dissolved oxygen, temperature, pH, and conductivity. Maine
Department of Environmental Protection (ME DEP) has collected grab samples on a weekly basis during
summer, and data on dissolved oxygen, E. coli or fecal coliform bacteria, phosphorus, total Kjeldahl
nitrogen (TKN), nitrate (NO3), ammonia (NH3), and conductivity are available for several years. The most
44
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Table 4-14. Existing Source Controls/Municipal BMPs
Source Control/BMP Description
Street Sweeping
Frequency
Equipment
Catch Basin Cleaning
Frequency
Equipment
Roadway Sanding and Salting
Sand:Salt Ratio
Salt used (tons/road mile)
Special reduced-use zones
Solid Waste Management
Residential
Commercial
Recycling program
Composting program
Other Existing Controls/BMPs
Household hazardous waste
Fertilizer and pesticide usage
Animal waste removal
Illicit connection identification
and removal
Storm drainage system
maintenance
All roads once a year; downtown, greater frequency
City owns two mechanical and one vacuum sweeper, and leases one mechanical
sweeper
2,750 catch basins exist; about 1,500 are cleaned each year, April through November
City owns a Vac-All catch basin cleaner
6:1
15,000 yd3/yr sand; 3,000 tons/yr salt
None
By city; once a week; downtown areas twice a week; three fall leaf pickups
By commercial haulers
Curbside once a week, newspapers/cans/clear glass; dropoff for all residential as well as
commercial, scrap metals/office paper/magazines and other materials
None; home composting is encouraged by the city
Waste oil dropoff for residents; no other program
None
Dead-animal pickup on roads only; no program to remove animal wastes
No removal program currently in place; some cross-connections have been identified
General maintenance activities use 25% of annual Highway Department staff labor hours
comprehensive set of data available was collected by International Paper Company relative to its
wastewater discharge upstream of Lewiston. Although the available data do not cover the entire reach
of the Androscoggin River in Lewiston, significant data on fisheries and sediment exist. None of the
existing data were oriented towards definition of wet-weather impacts in the receiving water. Some of
the ME DEP grab samples were taken during or after storm events, and the bacteria data indicate
elevated bacteria levels during these periods.
Because of the limitations in available data, two major areas of data collection were decided upon. The
first is data on CSO flows, loads, and impacts, required as part of CSO planning efforts by the state.
The second is information on selected city water resources where no data currently exist. These
programs are described in the following sections.
CSO Data Collection
The CSO data collection program, being conducted in 1993, encompasses two major elements: CSO
and storm water discharges, and receiving waters. Flow and water quality data are being collected for
several storm events for several of Lewiston's CSO discharges. These data will be used to calibrate a
computer model of the sewer system. Data are also being collected on several separate urban storm
drain discharges to identify the quality of storm water discharge to the receiving waters.
Dry- and wet-weather sampling is being conducted at four locations on the Androscoggin River, and at
two along Jepson Brook, where many of the CSOs discharge. Sampling is being conducted over a 2-day
period during and after several storm events. Sampling is also being conducted during dry weather to
45
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Table 4-15. Lewiston Existing Structural Controls
Structure
type
"type of
control
Location
Ownership
Receiving
water
Year
constructed
Design
criteria
Land use
Inspection
schedule
Maintenance
schedule
Kensington
Terrace
Phase II
Detention
pond
8-inch orifice
48-inch
orifice stand
pipe
Southerly
side of
Sherebrook
Extension
City of
Lewiston
Tributary to
No-Name
Brook
1990
2-yr and
25-yr storms
Neighborhood
Conservation
"A" and Res
None
None
Turnpike
Industrial
Park
Two
detention
ponds (P1
andP2)
P1: 12-inch
orifice
P2: 18-inch
orifice
P1: North of
Cottage
Road
P2: South
of Cottage
Road
City of
Lewiston
Drainage
ditch to
Hart Brook
1990
25-yr storm
Industrial '
None
None
Chalet
Motel
Detention
pond
8-inch
orifice
Southwest
of Lisbon
Street
Chalet
Motel
Hart Brook
1992
25-yr storm
Highway
business
None
None
Super Shop
'n Save
Underground
piping
detention
system
6-inch by
3-foot 4-inch
orifice
Sabattus
Street and
Highland
Spring Road
Super Shop
'n Save
Tributary to
Garcelon
Bog/Jepson
Brook
1988
25-yr storm
Highway
business
None
None
Sand Hill
Estates
Detention pond
10-inch orifice
Southwest of
Woodille Road
City of Lewiston
Intermittent
stream to
Jepson Brook
1989
Volume = 0.52
acre-feet
Neighborhood
Conservation
"A"
None
None
Andrews
Pond
Small pond
48-inch
orifice
Bates
College,
behind
Olin Arts
Center
Bates
College
Jepson
Brook
Unknown
Not
available
Institutional
Office
District
Unknown
Unknown
Jepson
Brook Inlet
Structure
Inlet control
structure
Concrete weir
East of
Farwell Street
City of
Lewiston
Jepson Brook
1986
Not available
Neighborhood
Conservation
"A"
2-3 times/yr
None
Lewiston
Recycling
Facility
Detention
pond
8-inch
orifice
18-inch
orifice
West of
recycling
center
City of
Lewiston
Tributary
to Andros-
coggin
River
Scheduled
for spring
1993
25-yr
storm
Industrial
N/A
N/A
Table 4-16. Lewiston Source Input and Receiving-Water Data
Description Source
Source Inputs (Flow and Quality)
CSO
Storm water
Other NPS
Receiving Water
Physiographic and bathymetric data
Row characteristics
Sediment data
Water quality data*
Sediment data
Rshories data
Benthos data
Biomonitoring results
Federal standards and criteria
State standards and criteria
None
None
None
Some available; see water quality data below
USGS flow data
International Paper—Androscoggin River
ME DEP; USGS; CMP; Union Water Power Co.
International Paper—Androscoggin River
International Paper—Androscoggin River
International Paper—Androscoggin River
None
EPA
ME DEP
* Note: All water quality data in Androscoggin River only.
46
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establish background conditions. Data are being analyzed for several parameters including E. coli
bacteria, pH, dissolved oxygen, and temperature.
Water Resources Data Collection
Due to the absence of available data, collection of new data was recommended in the major watershed
tributaries (except for Jepson Brook, which is being sampled as part of the CSO sampling effort) as well
as in No-Name Pond. The details of the program will be developed after the CSO sampling effort is
completed in 1993. In general, the program will consist of dry- and wet-weather data collection at various
stations. Grab sampling is contemplated because the major purpose of this effort is to characterize the
quality of each water resource.
Case Study:
Pipers Creek Watershed Characterization
and Water Quality Assessment
The Pipers Creek watershed borders Puget Sound in northern Seattle, Washington. Pipers Creek is an
urban freshwater stream that drains a 3.5-square-mile watershed. Land use in the watershed is
approximately 56 percent residential and 12 percent industrial and commercial, with the remaining 32
percent left as open space. Figure 4-2 shows the creek and its watershed.
As part of an overall effort to improve water quality in Puget Sound and its tributaries, an NPS pollution
control plan was developed in 1989 and 1990 by the city of Seattle and the, Washington Department of
Ecology (WA DOE). The purpose of the plan was to develop a program of control measures to reduce
or prevent NPS pollution to Pipers Creek. The plan was 'developed after Pipers Creek was selected by
the WA DOE as one of the state's first early action watershed projects for NPS pollution control. The
plan was funded by the WA DOE through a grant to Seattle.
An early step in action plan development was characterizing the natural and manmade environments in
the Pipers Creek watershed to help determine the land use practices and physical conditions that
contribute to NPS pollution in the watershed. Also, existing water resource conditions were determined
by gathering and analyzing available water quality data for Pipers Creek. The results are summarized
in the "Pipers Creek Watershed Action Plan for Nonpoint Source Pollution: Watershed Characterization
and Water Quality Assessment" (WA DOE, 1990), which includes the data required to develop pollution
prevention and control measures for the Pipers Creek watershed.
The types of watershed and water resources data collected and used in the Pipers Creek characterization,
compared with the types of characterization data recommended for collection in this chapter, are shown
in Tables 4-17 and 4-18. In general, the full range of relevant baseline information was gathered, except
perhaps information that might have been available on certain potential pollution sources. While some
existing watershed data were found to be available, existing water resource, sediment chemistry, and
biological data were less complete. Water resource data came primarily from periodic sampling efforts
carried out by the Seattle Engineering Department and the Metro Wastewater Treatment Plant. In
general, samples were collected during dry weather and were collected for bacteria. Some wet-weather
data were also available. The major sources of data were the monthly fecal coliform sampling conducted
47
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Figure 4-2. Pipers Creek watershed.
48
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Table 4-17. Pipers Creek Watershed Characterization Data
Watershed Characteristics Type of Information Included
Environmental Data
Topography
Land use
Recreational areas
Soil and surface bedrock
Vegetation
Natural resources
Temperature
Precipitation
Infrastructure Data
Roads
Storm drainage systems
Sanitary sewer systems
Treatment facilities
Other utilities
Municipal Data
Population
Zoning
Land ownership
Regulations
Ordinances
Municipal BMPs
Potential Sources/Existing BMPs
Landfills
Waste handling areas
Salt storage facilities
Vehicle maintenance areas
Underground tanks
NPDES discharges and pollution
control facilities
Retention/detention ponds
Flood control structures
Description of topography focusing on steep areas subject to erosion
Detailed discussion of current and projected land use with map showing
residential, commercial, and recreational uses
General discussion of recreational lands
Description of soils and geology with emphasis on erosion potential
Detailed discussion of vegetative habitat with maps of watershed
Discussion of natural resources with maps of watershed
General discussion indicating average, high, and low temperatures
Fifteen years of data to calculate rain event durations and intensities
Description of roadways in watershed
Detailed discussion including map of major trunk drains
General description of sewerage system
Discussion of size and location of treatment plant and outfall
Not addressed
Detailed discussion including current and projected population data
Description including watershed zoning map
Description of the amount and location of land publicly owned
Detailed description of existing regulations and programs addressing potential
NFS pollution
Detailed description of ordinances addressing NPS pollution
General description of garbage disposal practices in the watershed
Not addressed*
Brief description of existing facilities in the watershed
Not addressed*
Not addressed*
Description of underground tank program and potential extent of problems
Treatment plant discussed but not flows and loads
Not addressed*
Not addressed*
* These sources may or may not exist in the watershed.
49
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Table 4-18. Pipers Creek Water
Receiving Water
Quality Characterization Data
Type of Information Included
Physlcal/Hydrologic Data
Tidal elevation
Row characteristics
Physlographte/bathymetric
Sediment physical characteristics
Chemical Data
Water quality
Sediment quality
Biological Data
Fisheries
Benthos
General
Other
Quality standards and criteria
No discussion of tidal influence on Pipers Creek
No available data on Pipers Creek flow characteristics
General discussion of physical characteristics
No physical sediment data available
Available water quality data from previous studies; data include sediments, metals,
pathogens, nutrients, and organics
Some available sediment heavy metal data from previous studies was discussed
General description of fish populations in watershed
No discussion of benthic data
Description of plant and animal life throughout the watershed
General description of federal and state water quality standards
by Metro at two stations in Pipers Creek since 1970 and a source tracing program conducted at 40
stations in Pipers Creek in 1987 and 1988. Some of these sites were sampled fewer than four times
and others were sampled more than 25 times. Other parameters were analyzed only on a sporadic basis.
Available data were summarized in text, tables, graphs, and maps to help develop a profile of existing
watershed characteristics and water resources. Based on this information, the need for collecting
additional water resource, sediment, and biological data was determined. The project team decided that
no additional data collection was needed before developing the action plan (see Chapter 9 case study).
Once the existing conditions of the watershed were defined, the project team conducted an initial analysis
of the NPS pollution problems using the available data. In this project, problems were defined as:
• Significant impairment of designated uses.
• Unfavorable conditions in comparison with similar watersheds.
• Relatively frequent exceedances of water resource standards.
• Lack of specific types of data that are necessary to quantify conclusions.
• Occurrences that contribute to NPS pollution.
Based on this qualitative assessment, the general problems identified included:
• Bacterial contamination
• Turbidity, sediments, and other solids caused by erosion
• Heavy metals
• Oxygen depletion
50
-------
• Organics from pesticides and petroleum products
• Nutrients (e.g., phosphorus)
According to available wet-weather data, these problems worsened during rainy weather. The
assessment concluded that urban runoff is the primary cause of pollution problems in Pipers Creek.
More specific evaluations of NPS pollution could not be accomplished with the available data, and the
project team proposed collecting additional data in conjunction with the implementation of preliminary
pollution prevention measures. The areas requiring additional data collection are:
• Storm-related receiving water and storm runoff quality data.
• Periodic dry-weather sampling throughout a larger area of Pipers Creek.
• Flow and tidal data to help isolate specific sources.
• General biological sampling to determine the water body's overall health.
While the lack of such data prevented the project team from recommending specific structural BMPs to
address identified pollution sources, the team determined that a general pollution prevention program
focusing on municipal, regulatory, and public education approaches should be implemented as a first
step. In addition to these measures, the program team incorporated additional water quality monitoring
and implementation of structural demonstration projects to collect more data.
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
Anderson, J.R. 1976. A land use and land cover
classification system for use with remote sensor data.
U.S. Geological Service. Professional paper no. 964.
U.S. EPA. 1992. U.S. Environmental Protection Agency.
Storm water quality control in the Merrimack River
Basin. U.S. EPA Region 1. Boston, MA.
WA DOE. 1990. Washington Department of Ecology.
Pipers Creek watershed action plan for nonpoint
source pollution: watershed characterization and
water quality assessment. Olympia, WA.
Woodward-Clyde Consultants. 1989. Santa Clara
Valley Nonpoint Source Study Volume II: NPS
Control Program. Santa Clara Valley Water District.
51
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Chapter 5
Collect and Analyze Additional Data
Urban runoff pollution problems are rarely clear cut.
While information from existing studies might be
sufficient to understand certain issues, new data often
must be collected before the assessment and ranking
of problems or the screening and selection of BMPs.
Because of the diffuse and intermittent nature of urban
runoff pollution, its characteristics are difficult to quantify.
Nonetheless, documentation and quantification of pollutant
characteristics and effects are critical in developing an
urban runoff pollution prevention and control plan. Data
collection activities are often the most expensive aspect
of the urban runoff planning process. A common pitfall
in urban runoff programs is expending extensive
resources on collecting data that turns out to be of
limited value to the overall planning. Data collection
efforts therefore should be carefully planned with very
specific objectives given the difficulty in characterizing
urban runoff:problems. In this way, only data that is
necessary and valuable to the program are collected,
saving scarce program resources for implementation of
controls. i
This chapter describes how to develop a data collection
program that supports the urban .runoff pollution
prevention and control planning process. The chapter
first outlines possible goals and objectives of data
collection and the general types of data required
depending on the program. Important factors in
developing a data collection program are highlighted,
including selection of parameters, selection of sampling
stations, and frequency of data collection. Planning the
data collection work is then discussed, including work
plan development, sample analysis, and quality
assurance/quality control. Executing the program is
then discussed, including sampling techniques for water
resource, hydrologic, and rainfall data collection. The
chapter ends with a discussion of management and
analysis of the collected data, including various
methods for analyzing and presenting the data.
Objectives of Data Collection
The scope of a data collection program for urban runoff
pollution investigations must be site specific. It should
reflect the data needs determined during analysis of
existing conditions in conjunction with initial program
goals identified in the planning process. Data needs
may focus on potential pollution sources; water
resource problems; compliance with local, state, and
federal regulations; or other issues. A discussion of
typical data collection objectives at this stage of the
program follows.
Assess Existing Conditions
If existing data are not sufficient to establish current dry-
or wet-weather conditions, additional data are needed.
Dry-weather sampling of water resources could include
areas affected by urban runoff loading and areas
upstream of, and therefore not influenced by, the urban
runoff discharges in the watershed. It might also include
sampling of dry-weather base flows entering the water
resource through creeks, pipes, or ditches which could
contain illicit connections. In addition to water sampling,
sediment and biological sampling are particularly useful
for determining a water resource's relative health, as
discussed in the Chapter 6 case study. Also, sampling
of habitats, wildlife, soils, and other components of the
watershed might be required to establish existing
conditions.
Wet-weather sampling can be used to determine runoff
pollutant concentrations and to observe their
downstream effects. Wet-weather sampling is critical in
urban runoff pollution prevention and control planning
because most of the source loadings occur in wet
weather. Sampling of runoff and measurement of flow
in both sources and receiving waters during a storm can
be used to determine the variability of runoff volumes
and pollutant loads and to assess receiving-water
impacts for a particular storm. Results from sampling of
receiving waters during storms can be used to evaluate
the effects of storm water runoff on ambient water
quality, violations of water quality standards, and the
effects of storm water on beneficial uses. Other types
of wet-weather observations could be useful to assess
flow paths, ponding, areas of erosion, and other wet-
weather conditions in the watershed.
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Retina Problem Identification
Data collection programs might focus on collecting the
additional information needed to identify problems
clearly, such as pollutant sources and water resource
impacts, that first were identified during the existing
conditions assessment. These data can provide the
basis for source identification, problem assessment,
and BMP selection. Data collection for problem
identification could again involve dry- or wet-weather
sampling of sources, receiving waters, or watershed
factors.
Calculate Pollutant Loads
Flow concentration data from sources of pollutants
collected in dry or wet weather, as appropriate, can be
used to estimate pollutant loadings and to identify
priority pollution sources and watersheds. Pollutant
loadings may be estimated using numerous methods
ranging from simple to complex (see Chapter 6). These
estimates can be used to evaluate event or annual
pollutant loadings from the watershed, evaluate
resource impacts, and select appropriate BMPs.
Provide Data for Computer Models
Computer models can be used as predictive tools to
assess problems and the potential benefits of
alternative pollution prevention and control strategies
(see Chapter 6). Quantitative models that are calibrated
and verified using data from site-specific sampling
programs can be used to estimate impacts of future
pollution loadings anticipated under potential control
strategies. Models quantify pollutant loads as well as
assess impacts on receiving waters or other ecosystem
components. These models often require particular
types of input data that might have to be collected.
These typically involve dry- or wet-weather source flow
and concentration data, but can also include other
specialized parameters. For example, data on sediment
oxygen demand in the receiving water might be needed
if dissolved oxygen modeling is a primary concern, or
physical and chemical characteristics of street surface
solids might be tested if pollutant buildup and washoff
is to be simulated.
Address Important Pollution Sources or
Resource Areas
The monitoring program might need to focus on known
or suspected major pollution sources, to supplement
available data and confirm the existence of pollutant
loading from a source. Pollution sources could be
either point or nonpoint sources expected to be of
particular importance to the program. The monitoring
program also might need to focus on critical resource
areas. Natural resources that could warrant special
consideration for sampling include shellfish beds,
wildlife sanctuaries and refuges, wetlands, coral reefs,
spawning grounds, recreational fishing areas, bathing
beaches, and drinking-water resources.
Fulfill Regulatory Requirements
Specific regulatory programs might require collection of
certain data types. As discussed in Chapter 2, programs
such as the NPDES storm water permit program have
specific data collection requirements. As another
example, flow and quality data at CSO outlets might
have to be collected to satisfy state CSO planning
requirements.
Each data collection program should be developed
based on one or a combination of the above objectives,
or other objectives as appropriate. Data should be
collected only if a specific purpose relevant to the
program is fulfilled.
Data Collection Programs
Developing a data collection program depends on
numerous factors. The program should have clear
objectives, as discussed in the previous section of this
chapter. The program should also reflect the
goal-setting process described in Chapter 3. Design of
the data collection program also depends on factors
such as the size and nature of the watersheds and
receiving waters. The plan must take into account
available funding, resources, and schedule constraints.
This section discusses how to implement urban runoff
data collection programs. First, the major elements of
designing a data collection program, including selection
of parameters, sampling locations, and sampling
frequency, are summarized. The selection of an
analytical laboratory, laboratory methods and data
quality assurance procedures are then discussed.
Finally, the chapter discusses how to conduct the
sampling program, including water sampling, sediment
sampling, and hydrologic and rainfall monitoring. Some
of the numerous, detailed technical references on
monitoring that this handbook is not attempting to
reproduce are included in Appendix A.
Designing the Data Collection Program
"Since data collection programs are site specific and
varied, providing detailed guidance on what should
"typically" be done is not realistic. This chapter opens
with an overview of the type of objectives often
established. The major considerations in design of
a data collection program—parameter selection,
sampling station selection, and the frequency of data
collection—are presented in this section.
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Selection of Parameters
Parameters to be measured during the sampling
program should be selected based on the review of
existing conditions; the program's overall goals; the
specific objectives of the data collection program; and
the requirements of local, state, and federal regulations.
For example, most state water quality standards have
numeric limits for indicator bacteria levels in waters
intended for swimming and boating. If local beaches are
threatened by bacterial contamination from storm water
or CSOs, bacteria sampling needs to be included in the
program.
Given the long list of potentially important parameters,
site-specific considerations drive the selection .of
parameters to be tested. The most common pollutant
categories associated with urban runoff are solids,
oxygen-demanding matter, nutrients, pathogens, and
toxic substances as discussed in Chapter 1. The
sampling plan may include analysis of specific
parameters included in these or other pollutant
categories (see Table 1-3). Table 5-1 lists the most
commonly identified priority pollutants in the Nationwide
Urban Runoff Program (NURP). Specific pollutant
Table 5-1. Priority Pollutants in at Least 10 Percent of
Nationwide Urban Runoff Program Samples (U.S.
EPA, 1983a)*
Table 5-2. Storm Water Sampling Parameters (U.S. EPA, 1991a)
Metals and Inorganics
Antimony
Arsenic (50%)
Beryllium
Cadmium
Chromium (60%)
Copper (90%)
Cyanide
Lead (95%)
Nickel
Selenium
Zinc (95%)
Pesticides
Alpha-hexachlorocyclohexane
Alpha-endosulfane
Chlordane
Lindane
Halogenated Aliphatics
Methane, dichloro
Phenols and Cresols
Phenol
Phenol, pentachloro
Phenol, 4-nitro
Phthalates Esters
Phthalate, bis(2-ethylhexyl)
Polycyclic Aromatic
Hydrocarbons
Chrysene
Fluoranthene
Phenanthrene
Pyrene
* Frequency of detection in parentheses when 50% or greater.
parameters are required for characterizing storm water
as part of an NPDES permit application for a municipal
storm sewer system discharge (Table 5-2).
Based on more recent data than NURP's, the most
commonly detected organic compounds are shown in
Table 5-3 (U.S. EPA, 1990a). In this same study, seven
metals (aluminum, cadmium, chromium, copper, lead,
nickel, and zinc) were tested for both filtered and
Sediments/Solids
Total dissolved solids (TDS)
Total suspended solids (TSS)
Bacteria
Total conforms
Fecal conforms
£ co//
Enterococci
Fecal streptococci
Nutrients;
Total phosphorus
Dissolved phosphorus
Total nitrogen
Total ammonia
Organic nitrogen
Other
pH
Cyanide
Biochemical oxygen demand
(BOD)
Chemical oxygen demand
(COD)
Metals
Antimony
Arsenic
Beryllium
Cadmium
Chromium (total)
Chromium (hexavalent)
Copper
Mercury
Nickel
Selenium
Silver
Thallium
Zinc
Organics
Volatile organic compounds
(VOCs)
Base/neutral and acid
extractable compounds (BNAs)
Pesticides/PCBs
Phenols
Oil and grease
Table 5-3. Detection Frequencies of the Most Frequently
Occurring Organic Compounds (U.S. EPA, 1990a)
Organic Compound
1 ,3-Dichlorobenzene
Fluoranthene
Pyrene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)fluoranthene
Bis(2-chloroethyl)ether
Bis(chloroisopropyl)ether
Naphthalene
Chlordane
Benzo(a)anthracene
Benzyl butyl phthalate
Phenanthrene
Frequency of Detection, %
23
23
19
17
17
17
14
14
13
13
12
12
10
unfiltered fractions from numerous source areas (i.e.,
roofs, parking areas, storage areas, streets, loading
docks, vehicle service areas, landscaped areas, and
urban creeks). Detection frequencies were very high for
every metal tested in the unfiltered samples.
The information in Tables 5-1 through 5-3 can be used
as a starting point and can be refined to reflect
program-specific needs. Other conventional parameters
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such as temperature, dissolved oxygen, turbidity, and
specific conductivity can be included as indicator
parameters to support specific assessments of urban
runoff pollution sources and receiving waters. It is also
important to characterize particle settling velocities,
particle diameters, and dissolved and nondissolved
chemical fractions for use in evaluating runoff
treatability and pollutant routing in the watershed and
receiving waters.
In addition to the source and receiving-water quality
parameters outlined above, sediment samples may be
analyzed for physical and chemical parameters, such
as grain size distribution, organic content, total organic
carbon (TOG), nutrients, metals, petroleum products,
polychlorinated biphenyls (RGBs), or other parameters.
As pollutants are partitioned between the dissolved and
particulate phase, sediment chemistry reflects the
portion of the particulate-bound pollutants that settle.
These pollutants can, through other physical and
chemical mechanisms, be introduced into the water
column. Sediment chemistry can indicate potential
pollution problems caused by the sediments, such as
the release of metals and other pollutants into the
water column and the depletion of overlying dissolved
oxygen (DO) as organic matter is broken down by
microorganisms.
The sediment characteristics reflect the long-term
effects of intermittent and variable urban runoff
discharges. These long-term effects could be more
significant than short-term water quality variations that
occur in response to individual runoff events. In fact, it
is easier and more cost effective to test sediments and
plant and animal populations in the affected areas than
to conduct sampling of the intermittent pollution sources
and receiving-water responses. The existing substrate
and communities integrate the cumulative effects and
can be characterized rapidly since they do not vary
extensively. Numerous runoff event samples are
necessary to obtain reliable statistics, however, and
such data gathering is expensive and time consuming.
Sampling of aquatic biota involves collecting biological
species from the water column and sediments to
determine the species diversity, dominance, and
evenness. This process can include sampling for
plankton, periphyton, macrophyton, macroinvertebrates,
and fish and determining the number and density of
populations in the water resource. In addition, physical
habitat indicators, such as substrate and plant types
and conditions, are useful indicators of pollution
impacts. As with sediment, these habitats reflect the
long-term effects of the intermittent urban runoff
Impacts. These effects might be subtle and take a long
time to occur, depending on the nature of the transport
mechanisms and receiving-water body.
Toxicity test sampling can be used to determine the
relative toxicity of storm water runoff from a conduit,
creek, or other flow stream that might be receiving
contaminants. Toxicity testing, an integral part of the
NPDES point source monitoring program, has been
included in several states' storm water permitting
programs. Toxicity test results also provide information
on the relative degree of chronic and acute toxicity,
which again reflect the period of exposure of organisms
to toxic effects. A thorough discussion of toxicity testing
can be found in the Technical Support Document for
Water Quality-Based Toxics Control (U.S. EPA, 1991b).
Selection of Sampling Stations
Sampling stations should be selected strategically so
that data collected from a limited number of stations
satisfy multiple sampling objectives. The major types of
sampling are watershed-based (urban runoff sampling)
and water resource-based (receiving-water and aquatic
ecosystem sampling).
Urban Runoff Sampling. Wet-weather generated
discharges (e.g., storm water, CSO, and NFS) can
contribute large pulses of pollutant load and could
constitute a significant percentage of long-term
pollutant loads from urban and suburban areas.
Wet-weather sampling can be used to characterize
runoff from these discharges, determine individual
pollutant source and total watershed loadings, and
assess the impact on receiving waters. Pollution
sources, tributaries, or entire watersheds can be
ranked by total pollutant load and prioritized for
implementation of pollution prevention and control
measures (see Chapter 6).
In selecting a site for urban runoff sampling during wet
weather, the following criteria should be considered:
• Discharge volume: Select sites that constitute a
significant portion of the flow from a watershed.
• Pollutant concentrations: Based either on historical
information or on land use or population density,
select sampling sites to quantify representative or
varying pollutant load sources.
• Geographic location: Select sites that permit sampling
of flows from major subwatersheds or tributaries to
permit isolation of pollutant sources.
• Accessibility: Select sites that allow safe access and
sample collection.
• Hydraulic conditions: Utilize existing flow measurement
devices, such as weirs or gaging locations, or sample
where hydraulic conditions are conducive to manual
or automated flow measurements.
Sampling should also include dry-weather flows from
storm drains or other structures to determine if they
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result from illicit connections, or from ground-water
infiltration. The magnitude of these dry-weather
discharges determines the need to identify and remove
these illicit connections. Detailed procedures for this
have been developed (U.S. EPA, 1993).
Water Resource Sampling. For the impact of urban
runoff to be assessed, the water quality of receiving
waters during normal dry-weather periods should be
known. Water quality data collected during dry-weather
conditions provide a basis of comparison to data
collected during wet-weather conditions. These data
are also needed to quantify dry-weather pollutant
transport from tributaries and ground-water flows. If
existing data are not sufficient to characterize current
conditions, stations should provide good spatial
coverage within the receiving waters. Based on initial
sampling results, the number of stations potentially
could be reduced. For example, if initial sampling
results show that a particular stream within a
watershed is of high quality, sampling coverage of this
stream could be reduced. Additional stations could be
added in response to expected changes in land use
(such as high-density development projects), which
might affect water quality. Critical stations, however,
such as those that previously indicated water quality
violations, need to be maintained. Also, use of existing
stations from other programs should be maximized.
Wet-weather sampling stations should be located to
assess impacts of significant urban runoff pollutants and
major storm drain systems and CSO outfalls. Receiving
water stations should include the dry-weather
monitoring stations for comparison. Additional stations
may be sampled within tributaries affected by storm
water, CSO, or other discharges and land use types of
particular concern.
Other general site selection criteria for receiving waters
include:
• History of available data
• Easy accessibility
• Safety of personnel and equipment
• Entry points of incoming sources or tributaries
• Adequate mixing of sources or tributaries
• Straight reaches, rather than bends
Sediment Sampling. Sediments in receiving waters
affected by urban runoff integrate the long-term effects
of dry- and wet-weather discharges because of their
relative immobility. Grab samples can be taken to
indicate historical accumulation patterns. Sampling
sites could be distributed spatially at points of impact,
upstream (or downstream) reference sites, areas of
future expected changes, or other areas of particular
interest. Selection of specific locations is subject to
accessibility, hydraulic conditions, or other aforementioned
criteria.
Biological Sampling. Benthic or bottom-dwelling
organisms are affected both by contaminants in the
water column and through contact or ingestion of
contaminated sediments. The type, abundance, and
diversity of these benthic organisms thus can be used
to investigate the presence, nature, and extent of
pollution problems. Comparisons of areas upstream
and downstream of a suspected pollution source
require that sampling locations have similar bottom
types, because physical characteristics affect both the
chemical composition as well as the habitat requirements
of organisms.
Regional data or indices might be available for
comparisons with local site conditions to determine
whether an ecosystem is stressed. An example of the
use of ecoregional data and biotic indices is presented
at the end of Chapter 6. Such data provide a reference
for comparison and might suggest appropriate habitat
types or areas to sample in determining the level of
pollution impact.
Frequency of Data Collection
The frequency of data collection significantly affects
program cost and should be determined judiciously
based on the need for sufficient data to develop
statistically valid conclusions. Information on
determining valid sampling frequencies is available
(U.S. EPA, 1983b). Wet-weather runoff sampling is often
limited to several events and selected representative
subwatersheds because of the large resource
requirements and high costs. Data must then be
extrapolated to other similar subwatershed areas and
used to calculate storm-related pollutant loading for an
entire watershed. Depending on the area's size and
number of watersheds, and on financial resources,
adequate characterization of storm water runoff from
different watersheds might require a phased approach.
Areas of most concern are sampled first, with
subsequent sampling to characterize other areas based
on a watershed priority sequence. Given the cost of
such sampling, collection of sediment and ecosystem
data that integrate the long-term effects of urban runoff
may be fruitful since they are relatively stable and do
not need to be characterized as frequently.
For water resources monitoring, the sampling schedule
should account for seasonal climatic changes as well
as seasonal land use activities, such as fertilizer
application in spring, or road deicing activities in winter,
that might influence water quality. In temperate areas
with pronounced seasonal changes, monitoring stations
are usually sampled at least seasonally. This is
especially important for sampling of aquatic biota. For
characterization of urban runoff sources, several
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sampling events are ordinarily scheduled during
worst-case conditions: In spring during snowmelt and
heavy rains when runoff and contaminant transport is
significant, or during summer conditions when streamflow
is low, receiving-water dilution is minimal, and contaminant
concentrations are potentially highest. In addition, the
relatively high temperatures in summer can affect
aquatic biota, as well as reduce the capacity of water to
maintain high DO levels and stimulate bacterial
metabolism, placing additional demand on oxygen
supplies in the water column. This scenario represents
worst-case conditions in areas that experience organic
and nutrient enrichment. In areas with fairly constant
climate, less emphasis is placed on seasonality, with
perhaps more attention placed on land use activities.
After the implementation of BMPs, additional data might
be collected to assess their effectiveness. Data
collection after BMP implementation is discussed in
Chapter 9.
Planning the Data Collection Program
After the data collection program is designed, more
detailed planning and preparation is necessary. This
planning includes development of a data collection work
plan, selection of analytical laboratories and methods,
and organization of the necessary staff and equipment
resources.
Quality Assurance/Quality Control
The sampling program should include a Quality
Assurance Project Plan (QAPP) to ensure the collection
of meaningful and cost-effective data. An EPA guidance
manual, Interim Guidelines and Specifications for
Preparing Quality Assurance Project Plans (U.S. EPA,
1983a) is designed to help EPA and its contractors
prepare QAPPs. Another EPA document, entitled
Guidelines for Preparation of Combined Work/Quality
Assurance Project Plans for Environmental Monitoring
(U.S. EPA, 1984), combines a work plan with revisions
to the QAPP format and includes a generic plan. The
elements of this plan, listed in Table 5-4, are discussed
below.
Title pages of QAPPs should include places for
signatures of personnel with approval authority.
Municipal programs may use this format for approval by
the project manager or other responsible individuals.
Additional information could include project name,
requestor, date of request, and date of initiation (U.S.
EPA, 1984).
The project description is intended to define the goals
or objectives of the project and how the plan will satisfy
those objectives. A subsection on data usage identifies
the recipients of the data and establishes their
requirements, thus ensuring that the plan will produce
Table 5-4. Typical Combined Work/Quality Assurance Project
Plan (Adapted from U.S. EPA, 1984)
1. Title page
2. Table of contents
3. Project description
A. Objective and scope statement
B. Data usage
C. Monitoring network design rationale
D. Monitoring parameters and frequency of collection
E. Parameter table
4. Project fiscal information (optional)
5. Schedule of tasks and products
6. Project organization and responsibilities
7. Data quality requirements and assessments
8. Sampling procedures
9. Sample custody procedure
10. Calibration procedures and preventive maintenance
11. Documentation, data reduction, and reporting
12. Data validation
13. Performance and system audits
14. Corrective action
15. Reports
usable and effective data. A description of the
monitoring network includes sampling site locations and
the rationale for their selection. A subsection on
monitoring parameters and frequency includes a list of
the types of samples to be taken at each site and how
they will be collected. These parameters are then listed
in a table that includes the number of samples, sample
matrix (e.g., water and sediment), analytical method to
be used by the laboratory, sample preservation method,
and sample holding time.
Fiscal information as to projected costs for sampling
labor, equipment and supplies, analyses, and
requirements for outside support may be included to
support a budgetary analysis of the project. This
information will ensure that available resources are
adequate and properly allocated to maximize the
project's effectiveness.
One section details the schedule for the project from the
conceptual stage through the completion of the final
report. This schedule aids in assessing the availability
of resources and arranging for outside support. A
following section details the project organization and
identifies individuals responsible for the various aspects
of the project, as well as other outside support. An
organizational chart is frequently included.
Data quality requirements (frequently subject to
regulatory and budgetary constraints) are determined
through input from data users, samplers, and analytical
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personnel and focus on the data needs of the program.
Objectives should be established prior to development
of a work plan. The objectives include the required level
of detection, analytical precision (repeatability of a set
of measurements), and accuracy (agreement of result
with true value) obtained from analytical results.
Accuracy and precision are identified through the use
of performance standards, analytical spikes and
surrogates, method blanks, and replicate samples.
Many of these approaches are parameter-specific, as
are the acceptance criteria. These considerations
should be discussed with the analytical support
personnel for the parameters to be sampled. Acceptable
criteria for various analytical methods are listed in the
federal regulations (40 CFR 136, Tables A and B).
Other quality assurance considerations include
representativeness (whether the collection samples
represent conditions and matrices that support the
program's objectives), comparability (whether the
analysis results can be compared with other data
bases), and completeness (whether the valid data
obtained satisfies the program's objectives). These
considerations are basic to the development of the
sampling plan, and are used to assess the success of
sampling efforts.
Detailed sections follow in the combined Work
Plan/QAPP that describe sampling procedures and
documentation of sample custody, equipment calibration,
and data handling. Sampling procedures can be
generally described, citing method-specific references
such as Standard Methods (APHA, 1992) for detailed
sampling considerations. Sample documentation typically
employs a chain-of-custody form that describes and
follows the transfer of each sample bottle. Every time
responsibility for the samples is transferred, signatures
are used and copies retained to document the
transaction. Equipment logbooks are maintained to
document maintenance, calibration, and repairs. Data
documentation includes provisions to meet the needs of
legal or scientific challenges to the data, as well as
quality control over data entry, transfers, and any
calculations performed.
The remaining sections of the combined work/QAPP
are used to document procedures to validate data, to
record performance of laboratory personnel and
equipment, to record steps for corrective action, and to
note reporting requirements. Data validation consists of
an objective review of the data base generated by the
project against criteria established prior to sampling,
including holding times, detection limits, and QA/QC
results for accuracy and precision. Performance audits
are done prior to making arrangements to ensure
laboratory capabilities, as well as during the program to
identify problems and institute corrective actions if
required. Corrective action provisions define how to
proceed in the event that QA/QC objectives are not met.
Reporting requirements include interim progress reports
to management personnel to document the status of the
project, as well as a final report that presents the results
and conclusions of the study, including a summary of
QA/QC performance.
Analytical Laboratories
Before undertaking the data collection program,
arrangements must be made to have the samples
analyzed by a laboratory. If the laboratory analyses are
not conducted inhouse, or if an appropriate laboratory
is not already under contract to the municipality, a
service contract can be developed with an outside
laboratory that specifies the number of samples, the
price per sample, the analytical methods to be used,
and a QA/QC plan.
A laboratory should be selected based on a number of
criteria, .including price, analytical capability, past
experience, reputation, and certification. In most
instances, laboratories that are state certified for
specific chemical analyses should be used. The
laboratory should be familiar with the type of sampling
program and the schedule. This familiarity facilitates
development of a scope of services, which, in turn,
helps ensure quality data and timely results. The
laboratory should be asked to provide a list of past
clients as references. The laboratory should have a
strong QA/QC program and sufficient capacity to handle
the volume and types of samples generated by a
multifaceted sampling program. Because of the
unpredictable nature of storms for wet-weather
monitoring programs, the laboratory must be available
to receive samples on short notice, including at night
and on weekends, and to perform analyses within the
required holding times.
Other important steps in selecting a laboratory include
comparison of costs per analysis or per sample, and
evaluation of savings through volume discounts for the
large number of samples that might be generated,
especially during wet-weather sampling. Turnaround
time for data submittal and the form of deliverable
offered are additional considerations. A turnaround time
of 3 weeks is considered reasonable for typical
analyses for nutrients, solids, and bacteria. Some
laboratories can submit results in digital format so that
it can be directly inputted to a database management
system. Many laboratories can supply bottles and other
equipment, such as coolers, for the preservation and
transport of samples and courier service for sample
pickup. Such details should be clearly communicated
before finalizing the contract for analytical services.
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Analytical Methods
Of the many analytical methods to determine the
pollutant concentration in water and sediments,
standard methods for water and wastewater, as
published in the Federal Register and Standard
Methods for the Analysis of Water and Wastewater
(APHA, 1992), usually achieve the desired objectives of
the program. The laboratory can modify these methods
based on the type of sample and the level of detection
required. For example, storm water pollutant
concentrations might be significantly greater than those
diluted by receiving water; therefore, methods for
analysis of pollutants in storm water might require less
sensitivity than methods used to analyze drinking water.
Other particulars of the type of sample (e.g., salt
water or fresh water) might dictate the analytical
method or sample preparation requirements for certain
parameters, such as metals. The desired detection limit,
or the lowest concentration that can be reliably detected
In a sample, should be determined in advance. As
mentioned, the Standard Methods text provides
complete documentation of applicable methods for
physical, chemical, and biological analysis. Specific
guidance on the analysis of pollutants as required under
the NPDES program is provided in the federal
regulations (40 CFR 136.3, Tables lAthrough IE). These
guidelines establish standard analytical methods,
detection limits for all parameters, and the volume of
sample required.
Organization of Resources
Resources required for the data collection include
personnel and equipment. Personnel should be familiar
with their roles and responsibilities as defined in the
work plan and the team leader and each crew chief
should visit the sites in advance. A health and safety
plan should be prepared which identifies the necessary
emergency procedures and safety equipment. Special
training might be required, particularly if potentially
hazardous chemicals are involved, or if confined space
entry (into manholes, for example) is required. The
Occupational Safety and Health Administration (OSHA)
sets forth requirements for worker safety and protection
while conducting such work.
Equipment also must be prepared in advance: An
inventory of all the necessary equipment should be
taken; all equipment to be used in the effort, such as
boats, motors, automobiles, and batteries, should be
checked; field monitoring equipment should be properly
calibrated and tested.
Specific sampling logistics vary with the objectives of
the program. For example, dry-weather sampling can
often be conducted during daytime work hours in an
unhurried manner, though sampling must be scheduled
appropriately to coincide with diurnal, tidal, or other
variations of importance to the program. By contrast,
investigations of wet-weather impacts in a large
sampling program could require several teams who can
mobilize with only a few hours notice to conduct
concurrent sampling at several locations. Receiving-
water sampling could frequently include sampling for
several days after the rainfall event to assess the
residual effects of urban runoff pollutant loads.
Wet-weather sampling requires thorough planning and
rapid mobilization to implement an effective sampling
program. It also requires specific and accurate
weather information. Local offices of the American
Meteorological Society can provide a list of Certified
Consulting Meteorologists who provide forecasting
services specific to the needs of a sampling program.
Radar contact can also be established for real-time
observation of conditions. If a sampling criterion
requires a minimum of 0.5 inches of rainfall because of
resulting CSO discharges, additional insight Into the
timeframe of heaviest rainfall can be developed. While
incurring an additional cost, these efforts could result in
significant savings in costs associated with false starts
and unnecessary laboratory charges.
The rainfall, darkness, and cold temperatures that often
occur when conducting wet-weather field investigations
render even small tasks difficult. Contingency planning
and extensive preparation, however, minimizes
mishaps and helps ensure safety. Prior to field
sampling, all equipment should be organized, sample
containers should be assembled, and the bottle labels
filled out to the extent possible. Labeling is best done
by writing directly onto the sample bottle with permanent
markers. If stick-on labels are used, they should be
waterproof and secured with clear tape. The label
should indicate the sampling event (e.g., storm #1),
station location or number, sample number, preservative
used, and the parameters for which the sample is to be
analyzed. The sample number is the most important
identifier, and should be unique to each sample.
Conducting the Data Collection Program
A comprehensive data collection program with both
source and receiving-water sampling can consist of dry-
and wet-weather monitoring including water quality,
sediment, and sampling of aquatic biota; flow
monitoring; and rainfall monitoring. This section
describes the common types of sampling used for urban
runoff programs.
Water Sampling
Sampling as part of an urban runoff control program
primarily involves collecting water samples, preserving
them, and transporting them to a laboratory with as little
change in character as possible. Certain parameters,
including temperature, pH, and dissolved oxygen, are
60
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measured in the field (in situ) because values for these
parameters can change substantially if measured from
a sample of water that has been disturbed of held for a
long time. These parameters are usually measured
using battery-powered instruments with probes placed
directly in the water; results are taken from a digital or
analog readout and values are recorded in a field
notebook.
For samples undergoing laboratory analysis, the
volume of sample required by the laboratory should be
considered. In addition, accurate measurement of many
pollutants requires specific sample container types,
container cleaning or other preparations, or specialized
collection techniques. After collection, sample bottles
should be placed in a cooler with bagged ice or reusable
ice packs. Glass bottles should be separated by plastic
bottles or packing material to prevent breakage during
transport to the laboratory. Documentation of analytical
methods, volume requirements, containers, preservatives,
and maximum holding times is provided in the federal
regulations (40 CFR 136.3, Table II), and detailed in
such documents as Standard Methods (APHA, 1992).
Sampling for water chemistry can involve a number of
approaches. The following terminology is referred to:
• Grab sample: Samples collected manually and
analyzed individually.
• Discrete sample: Individual samples collected at
specific times collected manually or automatically,
often combined to create a composite sample.
• Composite sample: Samples combined based on a
predetermined formula involving flow weighting, time
interval, or other approach.
• Automatic sample: Samples collected. using an
automated sampling device.
Grab samples usually are analyzed individually to
characterize conditions at the time of sampling. Many
parameters, such as nutrients and metals, may be
composited, but attention must be paid to preservative
requirements. If sampling protocols permit and program
objectives are satisfied, composites represent a
cost-effective approach to quantifying pollutant loads by
reducing the number of samples submitted for analysis.
Other analyses, including bacteria, oil and grease, and
volatile organic compounds (VOCs), cannot be
composited and individual grab samples must be used.
Urban Runoff Sampling. During wet-weather
sampling, water samples may be taken manually or by
automatic samplers installed at the sampling site
before the rainfall. Automatic samplers may be
installed in manholes to sample storm water or
combined sewer systems, or placed in enclosures next
to creeks or culverts to sample runoff. They can be
controlled by flow-measurement devices, by stage height
monitors, or by timers, permitting comprehensive
sampling of flow quality with minimal labor.
Automatic samplers may be used to collect discrete
samples into individual bottles at predetermined
intervals of time or flow rate, or to collect discrete
samples and automatically composite them directly into
one container using a pre-set formula. The option of
using discrete or composite sampling is dictated by the
objectives of the program and the parameters to be
measured. Automatic sampler units can be either
purchased, leased, or furnished as part of a contractor's
service.
Wet-weather sampling must be performed by two-
person teams to reduce the time required to sample
each station and for safety reasons. Typically, one team
can sample at least two stations if the stations are in
close proximity. Because of the typical rapidity of
rainfall-runoff responses, however, the area that can be
covered is limited. One team member typically fills
sample bottles while the other performs flow
measurements and records relevant information in a
field book, including station number, time, date, weather
conditions (e.g., rain intensity, wind intensity and
direction), and other observations, such as oil sheens,
odors, or the presence of foam.
Proper characterization of urban runoff, either by
manual or automated sampling, requires periodic
sampling of the flow stream. This sampling should begin
with the pre-storm condition, if possible, followed by the
"first flush," when rainfall first washes accumulated
contaminants from the surface of the watershed and
pollutant concentrations are highest, and should
continue through the duration of the rainfall event.
Storm water pollutant loadings can then be
characterized using discrete samples taken over the
course of the storm, or by creating a flow-weighted
composite based on the relative flow rate (or other
appropriate parameter) associated with each sample
taken. Flow measurement methods and an example of
flow-weight composited data are discussed later in this
chapter.
Receiving-Water Sampling. Sampling of receiving
waters to provide background water quality data and to
assess impacts from urban runoff pollutants could
range from manual collection of bacterial samples from
a stream to a full-scale oceanographic investigation of
a harbor using a sizable vessel and considerable
logistics. The important considerations are to sample
the parameters of concern using proper sampling
techniques (i.e., USDI, 1984; U.S. EPA, 1982; Plumb,
1981; APHA, 1992). Further references are cited in
Appendix A.
61
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Other considerations for sampling are specific both to
the program objectives as well as to the sampling
station location characteristics. For example, while
surface sampling of shallow, well-mixed systems, such
as streams, is adequate to assess water quality,
additional samples of a cross section of wider rivers
might be necessary to meet study objectives. Deeper
systems subject to stratification from salinity or thermal
conditions should include some form of vertical
sampling, which could entail samples taken separately
from several depths analyzed individually or composited
to yield one sample. Such a case requires the use of
sampling devices such as Kemmerer or Nansen bottles
which can be lowered to the desired depth and tripped
by a weight dropped from the surface to produce a
discrete sample. Instruments for in situ sampling of pH,
temperature, dissolved oxygen, or salinity also can be
lowered to specified depths, with measurements
transmitted to the surface by cable and recorded.
Sediment Sampling
Analysis of sediment chemistry data can indicate the
historic water quality. Water column contaminants are
concentrated in the sediments through mechanisms
such as sedimentation, adsorption, and organic
complexation.
Chemical and physical sampling involve the collection
of representative samples of sediments, with
methodologies dictated by the physical character of the
system (e.g., depth, substrate type) and the type of
analysis being conducted. In most cases, shallow-water
sediments can simply be collected by hand using a
stainless steel spoon, spade, or push-corer. Deeper
systems, such as lakes and estuaries, may require the
use of vessel-deployed grab samplers or corers. These
types of samplers are described in existing guidance
(U.S. EPA, 1990b) and Standard Methods (APHA,
1992). The grab or core is then subsampled in a manner
consistent with the requirements of individual analyses.
In most cases, the sample is placed in a plastic bag or
other container and transported to the laboratory in iced
coolers. While this approach is appropriate for physical
analysis and certain chemical analyses (e.g., carbon
and metals), some analyses require special containers
or preservatives. Parameter-specific requirements, as
well as the required volume of sample for various
analyses, are listed in methodological references
(Plumb, 1981).
Biological Sampling
Biological sampling of benthic organisms depends on
the water body and the type of organism being sampled.
Estuaries, lakes, and large rivers typically are sampled
by a grab sampler of specified area and penetration
depth. Samples then are screened through a sieve, and
the organisms retained on the sieve are transferred to
a sample bottle and preserved. Streams and small
rivers can be sampled using a variety of samplers, again
depending on depth, flow rate, substrate, and
community type. In addition, artificial substrates can be
employed which minimize the problem of locating
similar substrates in all sampling areas. Comprehensive
guidance exists for collecting biological samples using
these devices (U.S. EPA, 1990b).
Flow Measurement
Flow measurement of streams, rivers, and runoff in and
from drainage systems is needed to calculate pollutant
loads and to design BMPs. Flow rate measurements
can be made using a variety of methods: The
velocity-area method (ISO, 1979; USGS, 1982; USDI,
1984) can be used to estimate flow rates in streams,
rivers and other open channels. In this method, the
channel's cross-sectional area, as computed from
channel width and depth measurements, is multiplied
by flow velocity readings. Flow measurements should
be taken with a portable velocity meter at 20 and 80
percent of the depth, or at 60 percent of the depth at
regular intervals across the channel (Chow, 1959).
Flow measurements can also be made by automatic
devices installed in channels, storm drains, or CSO
structures (U.S. EPA, 1975). These devices utilize a
variety of sensor types, including pressure/depth
sensors and acoustic measurements of stage height or
Doppler effects from flow velocity. Data are stored in a
computer chip that can be accessed and downloaded
by portable computer. Data are processed based on the
appropriate pipe, flume, or weir hydraulic equations.
Field calibration of data using such equations is critical
because these types of data might be influenced by
surcharging, backwater, tjdal flows, and other complex
hydraulic conditions typical of urban runoff flows. Such
devices can be purchased, leased, or furnished as a
contract service.
Accurate flow measurements can also be made at
hydraulic control structures, such as weirs or flumes,
where the rate of flow is a function of the water
elevation. If project finances allow, portable weirs or
flumes can be purchased or leased and installed in
storm drains, sewers, or channels for taking flow
measurements during storms (USDI, 1984). Flow and
elevation can also be taken at concrete weirs or staff
gages owned by the U.S. Geological Survey. For weirs,
flumes, and other standard structures, records of stage
height taken at the time of flow measurements can be
used to develop a stage discharge rating that can be
used as a quick reference for future readings (USGS,
1982). Figure 5-1 provides an example of a stage
discharge rating curve for a river. In general, flow
measurement stations should have uniform channel
62
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lo-
a e —
5 —
4 —
3—
I \
8 10
River Discharge, cfs x 1,000
12
14
Figure 5-1. Example stage discharge rating curve.
conditions for six channel widths upstream to eliminate
any turbulence, to avoid tidal or backwater effects that
would interfere with flow patterns, and to allow adequate
mixing of upstream flow from tributaries (U.S. EPA,
1991a).
Rainfall Monitoring
Rainfall data are necessary to estimate the amount of
runoff generated during an event, which is then used to
predict runoff volumes and predict responses to events
of different magnitudes. Existing long-term rainfall data
might be available near the area from the network of
gages operated by the National Oceanic and
Atmospheric Administration. Because of the variability
in the possible distribution of rainfall over a relatively
small area, a network of rain gages might be necessary
to support these objectives. The number of gages
required depends on the size of the program, the area,
topography, season, and typical characteristics of local
rainfall events. Available resources for rainfall
monitoring should be concentrated in critical areas
under investigation. Guidance in determining rain-gage
network density is available (U.S. EPA, 1976).
Rainfall gages consist of two types: nonrecording
gages, which measure total rainfall, and continuous-
recording gages, which measure intensity over the
duration of the event. The latter type is more desirable
for most urban runoff programs because an understanding
of the time-varying watershed hydrologic response to
rainfall variations within a storm event can be gained
from such data. One type of continuous-recording gage
is the tipping-bucket gage, which records the number of
times a calibrated bucket is filled and subsequently
tipped and emptied into a larger reservoir. Other
continuous gages utilize a weighing mechanism to
record rainfall amounts.
Rainfall gages should be located in open spaces away
from the immediate shielding effects of trees or
buildings. Ground installations are preferable (if
vandalism is not a significant problem). Roof installations
are another option, and public buildings, such as police,
fire, or public works buildings, are often used. The
installation should be in an unobstructed area of the
ground or roof.
Cost Estimating for Data Collection
Programs
State and federal funding for urban runoff control
programs typically is limited; the burden of financing
these efforts therefore falls on a municipality. As the
data collection program is being developed, the cost of
the program should be considered. A cost estimate
should be prepared for the entire program, including
in-house and outside services from consultants and
analytical laboratories. If funding levels are not
adequate to complete the sampling program, the
63
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program should be redefined by scaling down the scope
of sampling (i.e., number of sampling stations and/or
sampling frequency) or by using a phased approach
and completing critical components first and other
components as funding becomes available.
Data collection for an entire municipal area with multiple
watersheds can be very costly, and might use up limited
resources that could be applied to actual
implementation of controls. Sampling limited but
representative areas and extrapolating this information
to other unmonitored areas might be more cost
effective. Although such extrapolation is risky and
should be done with caution, it might be necessary
given program budget constraints. As discussed earlier
in this chapter, a focus on ecosystem components
which integrate long-term effects (e.g., aquatic biota,
habitats, sediments) could yield valuable data at a more
reasonable cost.
Some large municipalities might have the in-house
resources to undertake a comprehensive urban runoff
sampling program, including staffing, equipment,
analytical capabilities, and the technical expertise
required for data interpretation. For smaller
municipalities, or those without extensive technical
resources, the sampling program should take full
advantage of technical assistance offered by state and
federal agencies; contracted laboratories can be used
for necessary analytical services.
The major cost elements of the data collection program
include the following:
• Personnel costs, in-house and/or contracted, for the
field effort.
• Laboratory analysis costs.
• Monitoring equipment costs.
• Miscellaneous equipment costs.
* Data analysis and reporting costs.
Each item should be estimated in as much detail as
possible. Labor costs should include direct salaries plus
overhead and profit costs for contracted work.
Laboratory analysis costs are often provided on a unit
cost-per-sample basis. Other equipment costs are
based on rental or purchase prices. Data analysis and
reporting will include technical labor plus clerical time,
and perhaps office supplies and computer costs.
Data collection cost estimates are highly site and
circumstance specific and range from several thousand
to millions of dollars. As stated earlier, it tends to be a
major component, often the largest single element, of
the planning program. Therefore, designing the program
to respond to appropriate objectives requires the utmost
care.
Data Management and Analysis
Since data collection programs generate large amounts
of information, management and analysis of the data
are critical to a successful program. Even small-scale
programs, such as those involving only a few storm
water and receiving-water monitoring stations, can
generate hundreds of pages and thousands of data
records. Monitoring these stations over time adds
significantly to the amount of data. Thus, a key
requirement is the ability to store large amounts of
environmental data in an accessible format, allowing the
data to be manipulated for a variety of analyses.
Methods to manage and analyze data are presented in
this section: spreadsheets, graphical presentations,
database management systems, and statistical
analysis. Examples of how these methods can be used
to assess a sample data set are given. These methods
can also be used to analyze existing data (Chapter 4).
More detailed methods of assessment, such as
watershed and receiving water modeling, are presented
in Chapter 6.
Spreadsheets
Selection of the most efficient method for data
management depends on the scale of the program. For
small-scale urban runoff programs, a computer
spreadsheet program can be used. Entry of data into a
computer format permits easy manipulations, such as
calculations and graphics. Whether a computer is
available or not, data records should be organized into
tables by sampling station. An example of such a table
is shown in Table 5-5. Parameters recorded during a
survey can be entered into columns of data, with each
row in the table representing a sampling event. For
storm event monitoring, each row can consist of
consecutive samples collected during the event. The
sample ID number, which should be unique to every
sample, can be used as the principal sample identifier
should data be exported to a GIS or other computer
applications.
Most spreadsheet programs can also be used to create
graphs of the data and to perform calculations. Once a
format has been developed for data entry, calculations
such as contaminant load or percent oxygen saturation
can be automatically performed as the data are entered.
An example of a format used to calculate nitrogen loads
(ammonia and total nitrogen) is presented in Table 5-6.
Spreadsheet files can be combined as required to
present selected information, perform investigations, or
export data to other computer applications such as GIS
(see Chapter 4) or urban runoff and receiving water
models (see Chapter 6).
\
64
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Table 5-5. Example Spreadsheet Format
Sample
6
10
23
38
42
47
51
61
65
69
75
Month
7
7
7
9
9
9
9
10
10
10
10
Date
Day
18
19
20
4
5
5
6
17
18
18
18
Hour
2030
0920
1020
1710
0656
1750
0003
1730
0525
1117
1714
River
Stage,
ft
2.31
2.34
2.15
2.61
2.59
2.55
2.63
2.48
2.72s
2.75
2.57
for Water Resource Data
Temp.,
°C
24.8
21.2
22.5
23.0
21.8
23.0
22.7
18.5
18.5
18.7
18.5
PH
7.7
7.7
7.8
8.3
7.8
8.3
7.6
7.6
7.6
7.1
7.3
DO,
rng/L
7.65
8.14
8.35
8.80
8.20
8.78
7.75
8.90
8.50
8.90
8.20
Conduc-
tivity,
mS/cm
0.23
0.23
0.22
0.20
0.20
0.20
0.19
0.19
0.19
0.19
0.19
Fecal
Coliforms,
MPN/100 mL
<20
20
<20
<20
<20
20
80
560
300
140
140
TSS,
mg/L
<1
1.2
<1
1.8
2.9
2.8
3.1
4.5
6.8
5.9
5.8
BODS,
mg/L
5.6
4.4
<4
<2
<2
<2
<2
<2
<2
3.2
<2
Total
Nitrogen,
mg/L
0.899
0.897
0.853
1.081
*
0.775
0.832
0.914
0.905
0.903
*
Total Phos-
phorus,
mg/L
0.061
0.033
0.030
0.142
0.113
0.122
0.153
0.059
0.049
0.065
0.048
* Sample not analyzed.
Table 5-6. Spreadsheet to Calculate Nitrogen Loads
Sample
6
10
23
38
42
47
51
61
65
69
75
Month
7
7
7
9
9
9
9
10
10
10
10
Date
Day
18
19
20
4
5
5
6
17
18
18
18
Hour
2030
0920
1020
1710
0656
1750
0003
1730
0525
1117
1714
Freshwater
flows, tf/s
19.4
20.5
12.1
35.9
35.3
33.1
37.1
28.0
45.3
49.2
33.9
Total Nitrogen,
mg/L
0.899
0.897
0.853
1.081
*
0.775
0.832
0.914
0.905
0.903
ft
TN Load,
kg/d
42.6
44.9
25.3
94.9
•ft
62.7
75.4
62.5
100.4
108.6
*
Ammonium,
mg/L
0.015
0.013
0.011
0.017
0.021
0.004
0.010
0.093
0.098
0.204
0.180
Ammonia
(NH4)
Load, kg/d
0.7
0.7
0.3
1.5
1.8
0.3
0.9
6.4
10.9
24.6
14.9
* Sample not analyzed.
Graphical Presentation
Graphic displays enhance data analysis and
interpretation. Plots translate large sets of data into
easy summaries. Another effective use of graphics is
the spatial presentation of environmental data, such as
on a hand-drawn or GIS-simulated map (see Chapter
4). Whether using the capabilities of spreadsheet
programs or a GIS, or plotting data on graph paper by
hand, a trend analysis for a particular parameter,
location, or sampling program can be developed from a
data set. Figure 5-2 illustrates a simple line plot of
routine monitoring data for fecal coliform data taken
monthly over a 1-year period. Figure 5-3 depicts fecal
coliform data at a receiving water station influenced by
a storm sewer during a 24-hour period after a rainfall
event. In both figures, the state water quality criterion
for fecal coliform bacteria is indicated and quick, visual
comparisons of the collected data to the criterion can
be made.
Database Management Systems
A computer-based database management system is
used to store collected data and to permit easy retrieval
for subsequent calculations and analyses. Database
design involves a knowledge of the database
management system being used and the requirements
of database manipulation and interaction with other
software. The data base can be coordinated with, or be
part of, a GIS. In addition, the data base can be used
65
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500
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Deo.
Sampling Month
Figure 5-2. Fecal coliform densities at Station A.
500
300
600
900
1200 1500
Sampling Time
1800
2100
2400
Figure 5-3. Fecal coliform densities at Station E.
as input to urban runoff and receiving water models (see
Chapter 6).
Types of sampling information that could be included in
the data base include: sample identification number,
type of sample (e.g., rain water), sampling date and
location, analyses performed, results of chemical
analyses, detection limits, name of laboratory, name(s)
of personnel collecting samples, dimatic information, and
comments regarding the sampling or analyses. Database
queries can request information that focuses on specific
attributes. For example, the user may select all dissolved
oxygen concentration data for a specific sampling location,
or the user may select all dissolved oxygen data below
a certain concentration from all stations to determine
compliance with water quality standards. More detailed
information concerning data bases is available in the
user manuals of database management software and in
the literature (Date, 1985; Korth and Silberschatz, 1986;
Maier, 1983; Hursch et al., 1988).
66
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Statistical Analysis
Statistical analyses can be conducted to establish
trends and comparisons of the collected data such as
pollutant concentrations and loadings associated with
specific sampling locations or storm events. Statistical
interpretation provides information that can be used to
determine characteristics of the data set such as
whether a concentration is high or low compared to the
others, the amount of variation among the data, and the
way in which the data are distributed. Statistical
methods can also be applied to results of biological
sampling of receiving waters and sediments. These
methods can be used to identify shifts in species
abundance and community structure which might result
from exposure to pollutants.
Commonly used statistical calculations are shown in
Table 5-7 and discussed in the following sections. Table
5-8 presents results for TSS samples from a CSO
monitoring program to illustrate the use of these
statistical calculations. This CSO monitoring program
included 10 sampling sites at combined sewer overflow
locations for two storm events (November 3 and 22).
Table 5-8 also includes estimates for flow-weighted
composites for comparison with the statistical values.
Flow-weighted composite data are frequently generated
when discrete sampling is performed within a storm
event, as discussed earlier in this chapter. Figure 5-4
depicts the results from one sampling site plotted
against the overflow discharge rate and rainfall
hyetograph to illustrate the relationship between flow
and discrete samples upon which the flow-weighted
composite value is based.
Measures of Location
Statistical measures of location describe the relationship
between various values in a data set, including the
mean, median, and frequency distribution. These
statistical values can be used to determine average
values and the most likely value of future sampling
results.
Mean. The arithmetic mean, or average, is calculated
by summing the observations and then dividing the
Table 5-7. Commonly Used Statistical Calculations
sum by the number of observations (see Table 5-7). A
mean value can be used as a benchmark for
comparison to individual data points or to regulatory
standards. In some cases, state water quality
standards employ the use of the geometric mean (e.g.,
bacterial standards). In this case, the individual
observations are multiplied, and the nth root (n =
number of observations) is calculated. Arithmetic
means for each station and an overall mean for the
entire storm are provided in Table 5-8.
Median. To obtain the median or central point value of
a data set, the observations must first be put into
numerical order and then divided into two equal parts.
If the number of observations is odd, the median is the
single middle value. If the number is even, the median
is obtained by calculating the mean of the two middle
values of the ordered list. Median values for each
station and an overall median for the entire storm are
provided in Table 5-8.
Frequency Distribution. Frequency distributions are
developed by dividing the range of data points or
observations into evenly spaced intervals and then
counting the number of observations that fall within
each interval. A relative frequency distribution is
obtained by dividing each number in the frequency
column by the number of observations in the data set
(Devore, 1987). A graphical representation of a
frequency distribution can be obtained by plotting a
histogram, or bar chart, of the intervals along the x-axis
and the number of observations along the y-axis.
Many types of environmental data are either normally
or lognormally distributed/Normally distributed data are
symmetric about the mean (which in the case of normal
distribution is equivalent to the median), with a
histogram that resembles the shape of a bell curve.
Lognormally distributed data could exhibit a curve which
is skewed to the right or left, or could be flatter or more
peaked than a normal curve. Storm water and CSO data
are often lognormally distributed.
Many statistical tests (parametric statistics) to
determine if mean values from two sets of data are
significantly different require that data be normally
Statistical Parameter
Arithmetic mean
Geometric mean
Variance
Formula
x = (x
X = "N
•i + x2 +...+ XnJ/n
'(X,i X X2 X . . . X X n)
Variable Definitions
Xn = value of the n* data point
n = number of observations in a data set
X|, Xi = variables that are being correlated
Correlation coefficient
s2 = pxl2-(£x,)2/n]/(n-1)
r = PCX, - x)(y, -
= [nS(X|)(y,) -
67
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Table 5-8. CSO Sampling Results for Total Suspended Solids
Sit*
003
Mean value
Median value
Flow-walflhtad
value
009
Mean value
Median value
Row-walghted
value
C1IC
WIK1"
Moan value
Median value
Flow-weighted
value
023
Moan value
Median value
Flow-weighted
value
080
Mean value
Median value
Flow-weighted
value
Date
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
Time
0525
0545
0615
0632
0632
0715
0815
0705
0805
0905
0745
0815
0845
0945
1045
1215
1215
1345
1100
1115
1145
1215
1245
1315
1415
1515
1515
TSS,
mg/L
35
31
38
48
46
31
42
37
38.5
37
160
110
63
111
110
109
400
120
73
58
29
20
18
25
103
58
105
150
91
110
55
44
46
14
26
28
67
50.5
58
No
data
Date
11/22
11/22
11/22
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/22
11/22
11/22
11/22
11/22
11/22
11/23
11/23
11/23
11/22
11/22
11/22
11/23
11/23
11/23
11/23
11/23
Time
1530
1545
2150
0215
0315
0535
0000
0015
0015
0210
0310
0410
0810
0115
0130
0300
0300
0400
0510
0510
0800
1820
1920
2020
2120
2120
2220
0020
0220
0520
1605
1620
1650
0105
0205
0405
0605
0905
TSS,
mg/L
27
33
48
16
49
22
32.5
30
27
100
110
160
49
44
77
66
78.5
71.5
59
80
140
180
190
76
30
24
31 '
90
78
45
38
71
33
11
12
15
13
58
160
50
52
83
110
140
49
45
74
21
30
33
63
47
42
Site
012
Mean value
Median value
Flow-weighted
value
003
Mean value
Median value
Flow-weighted
value
070
Mean value
Median value
Flow-weighted
• value
086
Mean value
Median value
Flow-weighted
Vdl(J6
088
Mean value
Median value
Flow-weighted
value
All Sites
Combined
Mean value
Median value
Date
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
11/3
Time
0650
0705
0735
0835
0935
0725
0740
0810
0910
0910
1010
1210
1025
1255
1325
0840
0855
0925
0840
0940
1040
1140
1240
1240
TSS,
mg/L
110
63
51
35
95
71
63
59
160
39
17
47
130
230
160
116
124.5
160
42
13
18
24
18 .
27
27
21
17
22
21
23
160
91
42
25
28
24
73
45
Date
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/22
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
11/23
Time
0130
0145
0215
0315
0415
0615
0615
0805
0015
0030
0200
0300
0300
0330
0430
0530
0720
0920
1605
0025
0225
0335
0540
0205
0220
0250
0350
0450
0550
0550
0750
TSS,
mg/L
68
200
170
170
60
21
22
23
102
68
82
44
32
22
190
360
110
120
73
40
31
122
91.5
58
150
140
340
230
170
67
183
160
266
780
240
150
310
230
51
47
41
257
230
161
104
66
68
-------
1.2
1.1
1
0.9
0.8
•a
E. 0.7
£ 0.6
0.5
0.4
0.3
0.2
0.1
0
LJLUU LLU
I
SITE 012
Novembers, 1992
Illlllilllllilllllllllllllllllllll
Row
—0.01 i
—0.02",
-120
-100
- 801
!
- 60t
- 40 '
- 20
5:00
6:00 7:00 8:00
Time of Day, a.m.
9:00
10:00
Figure 5-4. Relationship between flow and pollutant concentrations.
distributed. It is therefore necessary to determine
whether a particular data set satisfies this assumption
prior to employing parametric statistics. Tests for
normality (e.g., Kolmogorov-Smirnov one-sample test,
Sokal and Rohlf, 1969) are used to compare the data
distribution with a normal one to determine if it is
sufficiently similar.
Prior to comparisons with other data sets, such a test
was performed on the pooled data for all measurements
of TSS given in Table 5-8. A histogram of the pooled
(untransformed) data was made first (Figure 5-5), A
Kolmogorov-Smirnov one-sample test indicated the
data were significantly different from a normal
distribution (dotted line in histogram). A log transform
was then applied (Figure 5-6), and the test for normality
repeated. The transformed data were found to be
normally distributed. The transformed data now met the
assumptions for parametric statistical analysis. In the
event that all attempts at data transformations prove to
be ineffective, nonparametric statistics (e.g., Mann-
Whitney U-test) can still be employed for comparison
and assessment of data.
Many parametric and nonparametric tests can be found
in statistical packages for personal computers/These
statistical packages can easily access information from
data bases, and greatly facilitate the evaluation of the
data generated by a monitoring program.
Measures of Variability
Statistical measures of variability describe how closely
the data set is grouped around the mean value.
Statistical tests performed to determine significance
between two means require as a basic assumption that
the variance components of the two data sets are not
significantly different. The two most frequently used
measures of variability are variance and standard
deviation.
Variance. Variance is a measurement of the
dispersion of observations about the mean—the sum
of the squares of the differences between each
observation and the mean divided by the degrees of
freedom in the data set (see Table 5-7). The term,
degrees of freedom, equals the number of observations
minus 1.
Standard Deviation. The standard deviation is the
square root of the variance and is expressed in the
same units as the mean. For a normal distribution, the
data included in the range of 1 standard deviation from
the mean represent 68.26 percent of the total data set.
A range of 2 standard deviations from the mean
represents 95.44 percent of the data set and a range of
3 standard deviations from the mean represents 99.74
percent of the data set. For example, the standard
deviation in the pooled TSS data for all sites was 102
mg/L, indicating a high degree of variability when
compared with an overall mean value of 91 mg/L.
Confidence Intervals
To determine whether an estimated parameter
measurement such as a contaminant concentration
measured in a laboratory or forecasted by a model
represents the actual value of that parameter, the
69
-------
n
n
r-30
-24
-18
-12
-6
n
mg/L
Figure 5-5. Untransformad total suspended solids (TSS) data.
r-10
-8
I
-6
-4
-2
-L.O
log mg/L
Ftgura 5-6. Log-transformed total suspended solids (TSS) data.
70
-------
estimated value can be compared to a confidence
interval. A confidence interval can be interpreted as the
probability that an estimated value falls within the
calculated limits of the interval. For example, a
95-percent confidence interval indicates a 95-percent
probability that the estimated value falls within the
specified limits of that confidence interval. Thus, only 5
percent of the estimated values would fall outside of this
range. The technical details of deriving confidence
intervals are beyond the scope of this document;
however, there are numerous references that could be
useful, including Devore (1987) and other textbooks on
probability and statistics.
Correlation Coefficient. The correlation coefficient (r)
provides useful information concerning the relationship
between pairs of data, denoted as x and y. An example
would be the relationship between TSS concentrations
from a site and the area that contributes runoff to the
site. The value of r does not depend on which of the
two variables is labeled "x" and which is labeled 'V,"
nor does it depend on the units of x and y. Generally,
a correlation coefficient is considered weak if
0 < Irl < 0.5, strong if 0.8 < Irl < 1.0, and moderate
otherwise (Devore, 1987).
Analysis of Biological Data
The evaluation of biological data could involve a
number of statistical approaches, which include both
qualitative and quantitative methods. Qualitative methods
frequently include the use of indicator organisms whose
presence or absence indicates the level of water quality.
Quantitative methods include comparisons of biomass,
organism densities, and community indices.
Qualitative Methods, Indicator species have been
used for several community levels, including plankton,
fish, and benthic macroinvertebrates. For example,
phytoplankton species have been categorized as
indicative of clean and polluted water, and responsible
for taste and odor problems in reservoirs (APHA,
1992). Indicator species of organic enrichment and
other pollutants in marine systems have been
described by Pearson and Rosenberg (1978). In the
case of freshwater benthic macroinvertebrates and
fish, pollution-tolerant or -intolerant organisms have
been assigned index values corresponding to their
pollution tolerance (Hilsenhoff, 1977, 1987; U.S. EPA,
1989; summarized in U.S. EPA, 1990b). These index
values typically utilize scales of 0 to 5, or 0 to 10, to
indicate the level of tolerance to pollutants.
The use of benthic macroinvertebrate indicator species
is illustrated in results from a stream survey to assess
the relative impact of nutrients and other contaminants
from an area affected by sewage leachate (Figure 5-7).
In the survey, EPT taxa (Ephemeroptera, Plecoptera,
Trichoptera = mayflies, stoneflies, and caddisflies) were
used to represent species sensitive to pollution, while
chironomid dipterans (blackflies), nonchironomid flies,
and oligochaete worms were used to represent
pollution-tolerant organisms.
The results reflected a fairly even distribution of the four
groups of organisms at the upstream control site (Site
A). Pollution-tolerant species, particularly the oligochaete
worms which are good indicators of organic enrichment,
were found in elevated numbers downstream of the
impact area (Site B). Further downstream (sites C
through E), the relative abundance of the four groups of
organisms came to reflect conditions found at the
upstream control site. In many urban environments, it
might be difficult to find an upstream control site. This
is common for feeder streams and creeks which
originate within the urban area such that the entire
reach is impacted. In such cases, it is necessary to
consider reference sites in other areas which are not
affected. .
Quantitative Methods. Quantitative methods to
analyze biological data utilize results for biomass,
number of organisms, and species composition.
Statistical methods described in earlier sections are
used to interpret numeric data on biomass and
densities. Community composition is analyzed through
the use of diversity and similarity indices, which
examine the number of organisms and taxa to
determine if communities are stressed by pollutants. A
number of these indices exist, which are described in
the literature (Washington, 1984).
The most frequently used diversity indices describe
species diversity, dominance, and evenness (Table 5-9),
which provide the basis for comparisons of results from
different sampling stations and study areas. Because of
the influence of natural variability on the distribution of
species, such comparisons are restricted to similar
habitats such as fast-moving sections of a shallow
stream (riffles), or deeper pooled areas. These indices
have been employed in ecological studies for a number
of years, permitting comparisons with historical data bases.
Calculation of these indices using the data in the
stream survey (Table 5-10) mirrored the results for the
Table 5-9. Commonly Used Ecological Diversity Indices
Shannon-Wiener Diversity Index
Simpson's Dominance
Evenness
H'=£{ni/n[ln(ni/n)]}
where i = 1 . . . s
= H7ln(s)
where:
n, = number of individuals in a species i of a sample from a
population
n = number of individuals in a sample from a population
s = number of species in a sample or population (also called
richness)
71
-------
Table 5-10. Diversity Indices for Sewage Leachate-Affected Stream Samples
Station
A
B
C
D
E
Total Taxa
44
33
31
39
15
Mean Number of
Organisms per ft2
372.2
1261.9
1193.1
796
60
Diversity
2.932
1.196
1.864
1.541
2.273
Dominance
0.077
0.536
0.263
0.442
0.138
Evenness
0.77
0.34
0.54
0.42
0.84
distribution of indicator organisms illustrated in Figure
5-7. Diversity and evenness values were both highest
at the control Site A, and lowest at Site B, indicating the
shift toward opportunistic, pollution-tolerant species
which had a competitive advantage over less tolerant
species. These results can also be plotted in a manner
similar to the indicator species results. Statistical tests
to determine the significance of the observed
differences can be easily performed following the
methods of Solow (1993).
Similarity indices permit comparisons of results to a
reference station by calculation of similarity coefficients.
These similarity coefficients can be subjected to cluster
analysis, with the results illustrated through the use of
dendrograms which graphically group similar communities
together. Guidance exists using examples of the most
widely used indices (U.S. EPA, 1990b), including
examples of applying statistical methods described
earlier to determine the level of significance associated
with comparisons using these quantitative approaches.
A dendrogram for the Bray-Curtis coefficient calculated
from the stream survey example (Figure 5-8) illustrates
the similarities between sites influenced by the sewage
leachate (Sites B through D). The upstream control site,
A, and the most downstream site, E, clustered together,
indicating a high degree of dissimilarity with the sites
most influenced by the sewage leachate. Again, tests of
significance can be applied to the results, and are
typically included in statistical packages which are
available to run cluster analyses.
100
Legend
EPTTaxa
A Nonchironomid Diptera
• Chironomid Diptera
o Oligochaetes
Station
-Sewage leachate
Figure 5-7. Distribution of macrolnvertebrate Indicator species along a sewage leachate-affected stream.
72
-------
o —i
I
0.1
0.2 —
0.3 —
0.4 —
0.5 —
0.6 —
0.7 —
0.8 —
0.9 •
1.0 •
Bray-Curtis Index
Figure 5-8. Cluster analysis dendrogram for sewage-affected
stream survey results.
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
APHA. 1992. American Public Health Association.
Standard methods for the analysis of water and
wastewater, 18th edition. Washington, DC.
Chow, V.T. 1959. Open-channel hydraulics. New York,
NY: McGraw-Hill.
Date, C.J. 1985. An introduction to database systems.
Menlo Park, CA: Addison Wesley.
Devore, J.L. 1987. Probability and statistics for
engineering and the sciences, second edition.
Monterey, CA: Brooks/Cole Publishing Company.
Hilsenhoff, W.L. 1977. The use of arthropods to
evaluate water quality of streams. Dept. of Natural
Resources, Madison, Wl. Tech. Bull. No. 100.
Hilsenhoff, W.L. 1987. An improved biotic index of
organic stream pollution. Great Lakes Entomol.
20:31-39.
Hursch, C.J., and J.L. Hursch. 1988. SQL, the
structured query language. Blue Ridge Summit, PA:
TAB BOOKS, Inc.
ISO. 1979. International Organization for
Standardization. Measurement of liquid flow in open
channels. Case Postale 56-CH 1211* Geneva,
Switzerland. ISO Standard 748-1979E.
Korth, H.F., and A. Silberschatz. 1986. Database
system concepts. New York, NY: McGraw-Hill.
Maier, D. 1983. The theory of relational databases.
Computer Science Press.
Pearson, T.H., and R. Rosenberg. 1978. Macrobenthic
succession in relation to organic enrichment and
pollution of the marine environment. Oceanor. Mar.
Biol. Ann. Rev. 16:229-311.
Plumb, R.H., Jr. 1981. Procedures for handling and
chemical analysis of sediment and water samples.
Technical Report ERA/CE-81-1. U.S. Environmental
Protection Agency/U.S. Army Corps of Engineers
Technical Committee on Criteria for Dredged and Fill
Material. Vicksburg, MS: U.S. Army Waterways Exp.
Station.
Sokal, R.R., and F.J. Rohlf. 1969. Biometry—the
principles and practice of statistics in biological
research. San Francisco, CA: W.H. Freeman and Co.
776 pp.
Solow, A.R. 1993. A simple test for change in
community structure. J. Animal Ecology 62:191-193.
USDI. 1984. U.S. Department of the Interior. Water
measurement manual. Bureau of Reclamation Water
Resources Technical Publication. Washington, DC:
U.S. Govt. Printing Office.
U.S. EPA. 1975. U.S. Environmental Protection Agency.
Sewer flow measurement; a state-of-the-art
assessment. EPA/600/2-75/027 (NTIS PB-250371).
Washington, DC.
U.S. EPA. 1976. U.S. Environmental Protection Agency.
Methodology for the study of urban storm generated
pollution and control. EPA/600/2-76/145 (NTIS
PB-258743). U.S. EPA Office of Research and
Development.
73
-------
U.S. EPA. 1982. U.S. Environmental Protection Agency.
Handbook for sampling and sample preservation of
water and wastewater. EPA/600/4-82/029 (NTIS
PB83-124503). Cincinnati, OH: U.S. EPA Office of
Research and Development, Environmental
Monitoring and Support Laboratory.
U.S. EPA. 1983a. U.S. Environmental Protection
Agency. Interim guidelines and specifications for
preparing quality assurance project plans.
EPA/600/4-83/004 (NTIS PB83-170514). U.S. EPA
Office of Research and Development.
U.S. EPA. 1983b. U.S. Environmental Protection
Agency. Guidelines for the monitoring of urban runoff
quality. EPA/600/2-83/124 (NTIS PB84-122902). U.S.
EPA Office of Research and Development.
U.S. EPA. 1984. U.S. Environmental Protection Agency.
Guidelines for preparation of combined work/quality
assurance project plans for environmental monitoring.
Office of Water Regulations and Standards, QA-1, May
1984. Washington, DC.
U.S. EPA. 1986. U.S. Environmental Protection Agency.
Quality criteria for water, 1986. EPA/440/5-86/001.
Washington, DC: U.S. EPA Office of Water,
Regulations and Standards.
U.S. EPA. 1989. U.S. Environmental Protection Agency.
Rapid bioassessment protocols for use in streams
and rivers: benthic macroinvertebrates and fish.
EPA/440/4-89/001.
U.S. EPA. 1990a. U.S. Environmental Protection Agency.
Hazardous and toxic wastes associated with urban
runoff. In: Remedial action, treatment, and disposal
of hazardous wastes: proceedings of the 16th Annual
Hazardous Waste Research Symposium. EPA/600/
9-90/037 (NTIS PB91-148379). Washington, DC: U.S.
EPA Office of Research and Development.
U.S. EPA. 1990b. U.S. Environmental Protection Agency.
Macroinvertebrate field and laboratory methods for
evaluating the biological integrity of surface waters.
EPA/600/4-90/030 (NTIS PB91-171363). U.S. EPA
Office of Research and Development.
U.S. EPA. 1991 a. U.S. Environmental Protection
Agency. Guidance manual for the preparation of part
1 of the NPDES permit applications for discharges
from municipal separate storm sewer systems.
EPA/505/8-91/003A. U.S. EPA Office of Water
(EN-336).
U.S. EPA. 1991 b. Technical support document for water
quality-based toxics control. EPA/505/2-90/001.
Washington, DC: U.S. EPA Office of Water.
U.S. EPA. 1993. U.S. Environmental Protection Agency.
Investigation of inappropriate pollutant entries into
storm drainage systems, a user's guide.
EPA/600/R-92/238 (NTIS PB93-131472). Edison, NJ:
U.S. EPA Office of Research and Development.
USGS. 1982. U.S. Geological Survey. Measurement
and computation of streamflow: vol. 1—measurement
of stage and discharge; vol. 2—computation of
discharge. Water-Supply Paper 2175.
Washington, H.G. 1984. Diversity, biotic, and similarity
indices: a review with special relevance to aquatic
ecosystems. Water Res. 18(6)653-694.
74
-------
Chapter 6
Assess and Rank Problems
This chapter presents methods for evaluating available
or newly collected data in order to assess problems.
Problem assessments, as defined in this chapter, are
evaluations performed to determine the extent and
severity of urban runoff-related problems. Problem
assessments are used to determine the need for and
appropriate level of pollution prevention and control
measures for the program. It is important to consider
both existing and potential problems, so that the
program addresses resource protection, as well as
problems that already exist.
The first step is defining problem assessment criteria,
which are used to assess the extent or severity of an
urban runoff-related problem. Following this definition, the
most commonly used methods of problem assessment
are presented, including pollutant source assessments,
resource assessments, institutional assessments, and
goals and objectives assessments. Finally, methods for
ranking problems based on results of the assessments
are included in this chapter because of the complexity
of urban runoff problems and the frequent need to set
priorities. Results of problem assessment and ranking
presented in this chapter provide the basis for BMP
screening and selection in subsequent steps of the
planning process.
Problem Assessment Criteria
Problem assessments can address a wide range of
issues, including:
• The types of urban runoff pollution in the watershed.
• The extent to which these pollution sources adversely
affect resources.
• The institutional needs and constraints in addressing
the problems.
• The goals established for the program area.
Criteria for the assessment can be developed to
address these major issues, to determine the important
issues, and to provide a basis for problem assessment.
Only criteria considered most critical and helpful in
distinguishing between problems should be selected.
Assessment criteria, such as those listed in Table 6-1,
can be evaluated qualitatively or quantitatively. These
criteria are briefly described below and elaborated upon
later in the chapter in the discussion of assessment
methods.
Pollutant Source Criteria
Assessment criteria focusing on pollutant characteristics
and the pollutant sources that affect a resource are
among the most critical in determining which problems
should be addressed. Pollutant source criteria, such as
those listed in Table 6-1, describe the range of pollutant
characteristics and sources and the size of each source.
The distance between the source and the affected
resource and the mode of pollutant transport are also
useful assessment criteria. Pollutant loading during wet
weather versus dry weather can also be considered.
Tools useful in evaluating pollutant source criteria
include GIS and urban runoff models (described later in
this chapter).
Resource Criteria
Resource criteria assess effects on resources and aid
in determining locations where preventive and corrective
measures are needed. Water resources of various types
(e.g., ground water, surface water, and drinking water)
are often the driving force for such assessments, but
many other types of resources, such as biological,
wildlife, and infrastructure could be appropriate to
consider. Examples of these assessment criteria, as
listed in Table 6-1, describe the importance or value of
a resource with respect to issues such as habitat,
recreational use, and public water supplies. The current
and desired uses of a resource may be included as
resource criteria. The .degree to which a resource is
impaired and the type of impairment may also be
considered. Tools such as receiving-water models and
biotic indices (see the case study at the end of this
chapter) and habitat evaluation procedures are used to
assess the existing conditions and simulate responses
of the resources to potential preventive and corrective
measures. Information gathered during existing conditions
assessment (Chapter 4) and data collection and
analysis (Chapter 5) are useful in analyzing the
resource criteria. The relative health of each resource
75
-------
Table 6-1. Criteria for the Assessment of Pollution Problems
(Adapted from U.S. EPA, 1987a)
Pollutant Source
"type of pollutant
Pollutants typically associated with the source
Source magnitude/pollutant loading
Transport mechanisms to the resource (direct pipe, overland flow
or ground water)
Wat'/dry-woather trends
Resource
Existing use of the affected resource (type, status, and level of
use)
Designated or desired use of the affected resource
Type and severity of Impairment
Relative value of resource affected
Institutional
Available resources and technologies
Understanding of problems and opportunities
Appraisal of potential for solving the identified problem
Implemontability of controls
Applicable regulations
Muitiagoncy responsibilities
Funding sources and limitations
Public perception
Goals and Objectives
Water resource goals (water use objectives)
Technology-based goals
Land use objectives
Objectives of planner and sponsor
In a community and the desire of the community to
improve its quality helps determine the priorities for
implementation.
Institutional Criteria
Urban runoff-related problems can also be assessed
using criteria that focus on the institutional constraints
on regulators, owners, and the public. Institutional
criteria are based on applicable regulations, preferences
of the local authorities and regulatory agencies, funding
sources and limitations, multiagency responsibilities
and overlaps, and public acceptance of the program.
Interviews and meetings with interested parties,
including agencies, environmental groups, advisory
groups, and private citizens, can be conducted to help
develop institutional criteria. Questionnaires can be
prepared and distributed to help identify concerns.
Complaints, either filed with local authorities or available
through interviews with citizens, also provide useful
input. Knowledge of problems gained through public
interaction programs can help to ensure public support
of urban runoff pollution prevention and control
programs which are implemented later. Examples of
institutional criteria are listed in Table 6-1.
Goals and Objectives Criteria
Urban runoff problems can be evaluated with respect to
current and future goals. Using goals and objectives
assessment criteria, presented in Table 6-1, allows the
program team to focus on problems where preventive
or corrective measures would provide the greatest
benefit. One goal, for example, might be to increase the
usage of public beaches by improving the conditions of
degraded water bodies meant for swimming. Application
of goals and objectives criteria could identify where
corrective measures would provide the greatest benefit,
perhaps at beaches only slightly degraded and needing
only minimal cleanup before they are restored, or at
beaches in heavily populated areas where many people
could benefit from restoration of the water body. Goals
and objectives can be set for restoration of affected
resources, but protection of existing uses is as valid a
goal as restoration.
Methods of problem assessment, presented in the
following sections, use the criteria discussed in this
section as a basis for comparison and evaluation.
Pollutant Source Assessments
Pollutant source assessments address the type,
magnitude, and transport mode of pollution sources
(existing or potential) in a watershed or program area.
These assessments are frequently aimed at quantifying
the source flows and pollutant loads under various
conditions.
Source Determination and Data Evaluation
Urban runoff pollution sources can be defined using the
watershed description (Chapter 4) and other information
such as the type(s) of pollution affecting a water
resource, the pollutant transport mechanisms, the
characteristics of drainage patterns and drainage
structures, and the land uses in the program area.
Activities or land uses within a watershed that are, or
potentially could be, causing pollution problems need to
be identified. Pollutant types found in the watershed can
provide clues regarding the source(s) of the problems.
To isolate pollution sources, the watershed can be
divided into smaller areas so that individual pollution
sources can be tracked down. Depending on the size
of the watershed, a drainage basin can first be divided
into sub-basins, which can, if necessary, be divided into
individual tributaries, pipe systems, or -drainage
channels. Pollutant types typically associated with
certain activities or land uses are listed in Table 6-2,
76
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This information can be used to identify potential
sources. Problem sources can also be identified based
on resource conditions, such as eutrophication of a
water body resulting from excessive nutrients, or
closures of shellfish beds because of high levels of
bacteria. In addition, sediments from aquatic systems
and storm sewers can provide useful information for
identifying potential sources (U.S. EPA, 1991 a).
Pollutant Source Flow and Load Estimation
Computer modeling is valuable in quantifying the flows
and loads of pollution sources needed for pollution
source assessments. Models can be used to estimate
source strengths as well as to evaluate the
effectiveness of proposed corrective measures or
BMPs. Models available for urban runoff assessments
vary widely in complexity, ranging from simple
estimation techniques to sophisticated and expensive
computer models. The following discussion highlights a
number of commonly used methods, focusing on
models used to predict pollution characteristics in an
urban environment. Information on urban and
non-urban models is available from literature (U.S. EPA,
1987b,1991b; Nix, 1991; Walesh, 1989) and from
agencies that sponsor the models. Methods of urban
runoff modeling discussed in this section include the
constant concentration or unit load estimates,
preliminary screening procedure, statistical method,
universal soil loss equation, rating-curve or regression
approaches, and hydrologic and pollutant buildup-
washoff models.
Constant Concentration or Unit Load Estimates
Constant concentrations or unit pollutant loads, which
can be used to estimate pollutant source loads, can be
obtained from available data or estimated based on the
types and sizes of land uses in the watershed. Constant
concentrations can be coupled with runoff volume
estimates to calculate runoff loads or can be used in
hydrologic models to calculate time variable flows and
loads. The constant concentration or unit load method
is easy to use, and can be helpful as a first-cut estimate
to identify which areas within a watershed contribute the
largest pollutant loads. Wet-weather and dry-weather
conditions can also be evaluated separately, to
determine the relative contributions of pollutants during
these weather periods. This method can be facilitated
using a GIS with information such as wet- and
dry-weather pollutant concentrations from different
sources, land use or source boundaries, and quantities
of flow produced in each area. Constant concentrations
or unit loads can also be estimated using a
spreadsheet.
EPA's Nationwide Urban Runoff Program (NURP),
conducted from 1978 to 1983, is one example of a
comprehensive study of storm water runoff from
residential, commercial, and light industrial areas
throughout the United States. It contains a large data
base of pollutant concentrations and loads measured
during various storm events (U.S. EPA, 1983a). Other
data bases of storm water pollutant concentrations and
loads include Driver and Tasker (1990); Tasker and
Driver (1988); and U.S. EPA, 1974, 1977,1982a, 1990.
Such data bases, however, must be used cautiously.
For example, since the NURP data are based largely
on areas without sanitary waste or industrial waste
influences, they might not be representative of the
location being studied.
These types of data can be applied to source load
estimation techniques such as the constant
concentration or unit load method. For example, Table
6-3 presents median and mean values of event mean
concentrations (EMCs) derived from urban runoff from
EPA's NURP study (U.S. EPA, 1983a). Typical ranges
of concentrations of various pollutants found in rainfall,
storm water, combined wastewater, and wastewater
effluent are presented in Table 6-4. With the
aforementioned cautions, such values can be used as
first-cut estimates of pollutant loadings. Because of the
high variability of urban runoff data, however,
site-specific data are required to ensure the accuracy of
this or other methods.
Table 6-3. Water Quality Characteristics of Urban Runoff for
the NURP Site (U.S. EPA, 1983a; Adapted from
Novotny, 1992)
Site Median Site Mean
Event Mean Event Mean
Constituents
Total suspended solids, mg/L
Biochemical oxygen demand
(5-day), mg/L
Chemical oxygen demand, mg/L
Total phosphorus, mg/L
Soluble phosphorus, mg/L
Total Kjeldahl nitrogen, mg/L
Nitrate and nitrite nitrogen, mg/L
Total copper, fig/L
Total lead, ng/L
Total zinc, jig/L
Concentration
100
9
65
0.33
0.12
1.50
0.68
34
144
160
Concentration
141 to 224
10 to 13
73 to 92
0.37 to 0.47
0.13 to 0.17
1.68 to 2.12
0.76 to 0.96
38 to 48
161 to 204
179 to 226
Table 6-5 shows an example of the constant
concentration method used to estimate loadings of fecal
coliform bacteria and nitrate-nitrogen and to prioritize
nonpoint sources in a watershed. To estimate the
loadings, mean concentrations for different land uses
were multiplied by the estimated annual runoff volume.
79
-------
Tab)* 6-4. Charactarlatics of Rainfall, Storm Water, Combined Wastewater, and Treated Effluent (Adapted from various sources;
so* Metcalf & Eddy, Inc., 1991; Novotny, 1992)
PanurMttr Rainfall
Suspended solids, mg/L —
Biochemical oxygen demand 1 to 13
(5-day), mg/L
Chemical oxygen demand, mg/L 9 to 16
Fecal coliform bacteria, —
MPN/100 mL
Total phosphorus, mg/L 0.02 to 0.15
Total nitrogen, mg/L —
Total KjoWahl nitrogen, mg/L —
Nitrate nitrogen, mg/L 0.05 to 1.0
Total lead, pg/L 30 to 70
* Average value.
Storm Water
141 to 224
10 to 13
73 to 92
Combined
Wastewater
.,270 to 550
60 to 220
260 to 480
Primary
Effluent
40 to 120
70 to 200
165 to 600
Secondary
Effluent
10. to 30
15 to 45
. 25 to 80
1,000 to 21 ,000 200,000 to 1,1 00,000 — —
0.37 to 0.47
3 to 24
1.68 to 2.12
0 to 4.2
161 to 204
1.2 to 2.8
4 to 17
' —
— '
140 to 600
7.5*
35*
.— •
—
—
6* '
30*
—
— "
—
T«Wt 6-5. Estimated Urban Runoff Loadings Using Constant Concentrations (U.S. EPA, 1992)
Source Area,
ATM Description and Location , ac
A Main St and Freoport outlet stores 3.3
B Commercial development at I-95 30.6
Interchange, Main and Pine streets
C A portion of Freoport Crossing 13.9
outlets, Main St, Vamey Rd., and
KarKfean
D Main St., Vamey Rd., a portion of 21 .0
Unwood Rd., and adjacent
residential development
E1 Southern LL Bean parking lot 6.5
E2 Northern LL Bean parking lot 5.5
F Independence Way, Eastland Shoe 14.1
warehouse, Horsefeathers
Restaurant, and Main St
G Somerset Condominiums, Summer 38.0
St, Upper West St, and Freeport
Place Condominiums
H Municipal garage, Main St., and 15.0
town office parking lot
1 ' Downtown Village area along Main 19.2
St between Morse and West streets
including Oak
"Fecal coliform concentration = 16,000 org/100 mL,
6 Fecal coliform concentration = 17,000 org/100 mL,
° Fecal coliform concentration = 14,000 org/100 mL,
Fecal coliform concentration = 37,000 org/100 mL,
Annual
Runoff
% Runoff Volume,
Impervious Land Use- Coefficient Mgal
85 Commercial8
50 Commercial
60 Commercial
10 Multifamily
residential3
85 Industrial0
80 Industrial
20 Commercial
20 Single-" and
multifamily
residential
60 Industrial
Commercial
75 Commercial
0.73 2.7
0.45 15.7
0.61 9.7
0.13 3.1
0.73 5.4
0.69 4.3
0.21 3.4
0.21 9.1
0.53 9.1
0.65 14.2
Annual
Fecal
Coliform
Loading
org x 1fT2
(rank)
1.7(12)
9.8 (1)
6.0 (3)
2.0 (10)
2.8 (7)
2.2 (8)
2.1 (9)
•5.9 (4)
4.7 (5)
8.8 (2)
Annual
Nitrate
Nitrogen
Loading
Ib (rank)
14(11)
82 (1)
51 (4)
24 (8)
28 (7)
23 (9)
18 (10)
73 (3)
48 (5)
75 (2)
Quali-
tative
Ranking
Low
High
High
Low
Medium
Medium
Low
High
High
High
NO3-N concentration = 0.63 mg/L
NO3-N concentration = 0.96 mg/L
NO3-N concentration = 0.63 mg/L
NO3-N concentration = 0.96 mg/L
80
-------
Runoff volumes were based on the size, irnperviousness,
and land use of each source area. Table 6-5 presents
the estimated pollutant loadings for the watershed.
Based on this analysis, 5 of the 10 areas (B, C, G, H,
and I) of nonpoint source pollution were qualitatively
assigned ratings of "high" based on their pollutant
loadings. These areas contribute more than 75 percent
of the total pollutant loading in the watershed.
Preliminary Screening Procedure
Simple equations can be used to estimate annual
average loading contributions of urban runoff for 5-day
biochemical oxygen demand (BOD5), suspended solids,
volatile solids, total phosphate phosphorus, and total
nitrogen. The preliminary screening procedure is a
sophisticated unit load method which can be used to
calculate unit loads as a function of land use, population
density, and frequency of street sweepings (U.S. EPA,
1982b). Pollutant loadings can be estimated based on
the relative contribution of pollutants from each land
use; however, the equations are not location specific
and are useful, only for screening purposes. Using the
preliminary screening procedure, unit loads are
calculated by the following equation developed by EPA
(U.S. EPA, 1976a) as reported by Walesh (1989):
L = u(i,j)xPxPDFxSWF
where:
L = average annual amount of pollutant j
generated per unit of land use i, Ib/ac/yr
u(i,j) = load of pollutant j generated per
unit of runoff from land use i, in
Ib/acre-inch
P = average annual precipitation, in
PDF = population density factor, a dimensionless
parameter with a value for residential
areas of 0.142 + (0.218)(PD)°-5*,
where PD is a population density in
persons per acre, equal to 1.0 for
commercial and industrial areas, and
0.142 for institutional areas (e.g., parks,
cemeteries, and schools)
SWF = street-sweeping factor, a dimensionless
parameter; SWF =1.0 when streets are
swept infrequently, with the average time
between street sweepings being greater
than 20 days; for more frequent street
sweeping, SWF is less than 1.0 and could
be estimated from site-specific data or
literature values.
The unit pollutant loads (u) are obtained from measured
or estimated concentrations or loadings from various
land use or source areas.
Statistical Method
The statistical method of modeling urban runoff
assumes that EMCs are distributed log-normally and
characterizes EMCs by their median values and their
coefficients of variation. EPA's statistical method (U.S.
EPA, 1979) includes statistical properties of rainfall,
area, runoff coefficients, median EMCs, and coefficients
of variation of EMCs of various pollutants. The Federal
Highway Administration (FHWA) has implemented
EPA's statistical method for various locations in the
United States (Driscoll et al., 1989; Woodward-Clyde
Consultants, 1990a).
The runoff flow rate and volume from a mean event are
computed by the FHWA model using the following
equations:
MQR = Rv x MIP x ARW x (3,630/3,600) <;
MVR = Rv x MVP x ARW x 3,630
where:
MQR = average runoff flow rate for mean storm
events, ftVs
Rv = runoff coefficient (ratio of runoff to rainfall),
equal to 0.007 x IMP + 0.10, where IMP is
equal to the impervious fraction of the
drainage area, %
MIP = rainfall intensity for mean storm event, in/fir
ARW = drainage area of the highway segment, ac
MVR = volume of runoff for mean storm event, ft3
MVP = rainfall volume for mean storm event, in
The numbers 3,630 and 3,600 are dimensional
conversion factors.
The log-normally distributed EMCs are calculated by the
equation:
= TCRV(1+CVC2)
where:
MCR = EMC for site, mg/L
TCR = site median pollutant concentration, mg/L
CVC = coefficient of variation of EMCs
and the mean event mass load is computed by:
M(MASS) = MCR x MVR x (62.45 x 1 0"6)
where:
M(MASS) = mean pollutant mass loading Ib/event
MCR = mean runoff concentration, mg/L ,
MVR = mean storm event runoff volume, ft3
i- • i - . • ..'•;"
Universal Soil Loss Equation
The Universal Soil Loss Equation is primarily applicable
to agricultural areas and is used to estimate the soil loss
81
-------
and sediment yield from a homogeneous parcel of land
(U.S. EPA, 1976b). The discussion in this handbook is
general, and more detailed information can be obtained
from referring to more specific sources (SCS, 1977).
This method, relatively simple to use, considers such
factors as rainfall, erosive forces of the rainfall, soil
erodibility, slope, vegetative cover, and erosion control
practices. Since this method is used primarily to
estimate soil loss and, when modified, sediment yields
from non-urban, agricultural areas, it is less applicable
to the problems addressed in this handbook than other
methods discussed.
The Universal Soil Loss Equation is:
E = AxRxKxLSxCxP
where:
E = soil loss by water erosion in rill and inter-rill
areas, tons/yr
A = area, ac
R = rainfall factor, accounting for erosive forces of
rainfall and runoff, erosion index units/yr
K a soil erodibility factor reflecting the physical and
chemical properties of a particular soil,
tons/ac/erosion unit index
LS a slope length or topographic factor reflecting the
influence of vegetation and mulch,
dimensionless
C - cover and management factor reflecting the
influence of vegetation and mulch,
dfmensionless
P = erosion control practice factor that is similar to
the cover-management factor, but accounts for
practices on the land surface such as
contouring, terracing, compacting,
sedimentation basins and control structures,
dimensionless
In order to estimate sediment yield (as opposed to soil
loss), the equation is modified by adding a sediment
delivery ratio (Sa) as follows:
Y(S)E = AxRxKxLSxCxPxSd
where:
Y(S)g = sediment loading to stream, tons/yr
S . . . Xn x BCF
where: A
Y = estimated storm-runoff load or
volume, response variable
Po. Pi. Pz. Pn = regression coefficients, provided by
Driver and Tasker, 1990
X0, X17 X2, X3 = physical, land use, or climatic
characteristics, explanatory variables
BCF = bias-correction factor, calculated by
Driver and Tasker, 1990
Hydroiogic and Pollutant Buildup-Washoff Models
For larger and more complex programs, it may be
desirable to use hydrologic and pollutant buildup-
washoff models. These models address the accumulation
of pollutants during dry-weather periods and the
washing off of these pollutants during rainfall events. Of
the many models available, some of the more widely
used models that use a buildup-washoff mechanism
include Hydrological Simulation Program — Fortran,
HSPF (U.S. EPA, 1981); Storm Water Management
Model, SWMM (U.S. EPA, 1988b); Storage, Treatment,
Overflow, Runoff Model, STORM; and Source Loading
and Management Model, SLAMM (Pitt, 1989). These
models are described below. Table 6-6 compares these
urban hydrologic and pollutant buildup-washoff models
and the EPA statistical method as implemented by the
FHWA. Many other models are available which are not
described here.
HSPF, available from EPA, simulates movement and
storage of water in the hydrologic budget of a watershed
or drainage basin, from rainfall to streamflow to
ground-water storage. HSPF is useful when large
watersheds comprising multiple pollutants and land
uses are to be modeled and/or when issues such as
sediment erosion, pollutant interaction, and ground-
water quality of the system are of concern. Input data
requirements of this model are extensive and include
time series inputs of hydrologic and meteorologic data,
and input of characteristics describing pollutants,
topography, storage, response, and evapotranspiration.
HSPF can simulate receiving waters and pervious and
82
-------
Table 6-6. Comparison of Urban Runoff Model!! (U.S. EPA, 1991 c; Pitt, 1989)
Model
Attribute
Sponsoring Agency
Type of Method
Surface water— simple
Surface water— refined
Soil/ground water— simple
Soil/ground water— refined
Surface water— statistical
Simulation Type
Continuous
Single event
Hydraulic/Hydrologic Features
Rainfall/runoff analysis
Sewer system flow routing
Full, dynamic flow routing
Surcharge
Regulators, overflow structures
Storage analysis
Predicted Pollutant Concentrations in:
Runoff water
Surface water
Ground water
Predicted Pollutants
Conventional
Organic
Metals
Number of pollutants
Source/Release Types
Continuous
. Intermittent
Single
Multiple
Diffuse
Unique Features
Special solids routines
Treatment analysis
Degradation products
Data base
Uncertainty analysis
Input/execution manager
Level of Application
Screening
Intermediate
Detailed (suitable for design)
Data and Personnel Requirements8
Overall Model Complexity1
Available on Microcomputer
Storm Water
Management
Model (SWMM)
EPA
X
X
X
X
X
X
X*
X°
X
X
X
X
X
X
X
X
10
X
X
X
' X
X
X
X
X
X
X
X
X
X
. High
High
X
Hydrological
Simulation
Program — Fortran
(HSPF)
EPA
X
X
X
X
X
X
X
X
X
X
X
X
10
X
X
X
X
X
X
X
X
X
X
X
X
X
High
High
X
Storage,
Treatment,
Overflow, Runoff
Model (STORM)
Hydrologic Engineer-
ing Center (HEC)
X
X
X
X
X
X
X
6
X
X
X
X
X
Low
Moderate
Source Loading
and Management
Model (SLAMM)
Pitt"
X
X
X
X
X
X
X
10
X
X
X
X
X
X
High
High
X
Statistical
EPA
X
N/A
N/A
b
Xd
X
X
X
X
Any
X
X
x°
X
Moderate
Moderate
X
GI AR^&Jl ie a nVArxrtA+an/ rMrtdniI f\\nr^f\i4 l>\w D DIM Dbt Pi P^nnnvlwtnn* *•»< O!».!l EMM I MAM •.!•*«. 1 l«!..^u^.!^. _£ AI_L.___
. ——• «>"»»i >v w fn wf*i >w»*i j IIIVMVI VKIIWVI »*j i i> i iii( i ii
-------
Impervious lands and soils. Although it is complicated,
model documentation is available from EPA, including
copies of the model, user assistance, and periodic
training sessions (U.S. EPA, 1991d).
SWMM Is a complex model using finite-difference
approaches that can be used to simulate urban storm
water runoff and combined sewer overflows. Input data
requirements are extensive and involve information
such as precipitation, air temperature, channel and pipe
networks, land use patterns, and storage and treatment
facilities (U.S EPA, 1991d). SWMM can be used during
both the planning and design phases of a program. Its
output consists of hydrographs, pollutographs, and
control options and cost (U.S. EPA, 1991d). Model
documentation is available from EPA.
While the use of SWMM and HSPF requires a high level
of effort and expertise, the models also lend themselves
to more simplified treatment and simplified versions are
available. For example, in SWMM, the buildup-washoff
method of estimating pollutant contribution to a system
can be substituted with constant pollutant concentrations.
SWMM can also be run in a long-term mode using
variable time steps so both event-specific and
seasonal/annual conditions can be analyzed.
STORM contains simplified hydroiogic and water quality
routines for urban runoff modeling. While data
requirements of the model are minimal, the model is
less flexible than other, more complex models. Output
of STORM includes storm event summaries of runoff
volume, concentrations and loads, storage and
treatment utilization, and total overflow loads and
concentrations (U.S. EPA, 1991d). Although the
simplicity of STORM makes it an attractive model for
screening purposes, it has not been updated by its
agency sponsor, the U.S. Army Corps of Engineers,
Hydroiogic Engineering Center (HEC), since 1977.
While the model has been updated and refined by
private entities and many applications of STORM exist,
use of STORM has declined in recent years (U.S. EPA,
1991d).
SLAMM is a proprietary model which can be used to
evaluate the effects of pollution control measures and
development characteristics on urban runoff quality and
quantity. Model input requirements include rainfall
duration, depth of rainfall, areas of each pollution source
type, SCS soil types, building density, land use,
pavement texture, traffic density, and roof pitch (Pitt,
1989). The SLAMM model user manual incorporates a
discussion of the hydrology of small storm events and
its relationship to more "standard" hydroiogic models.
Investigations have shown the need to represent the
rainfall-runoff processes correctly for the more frequent,
smaller size storms since they often account for a major
part of the pollution loading (Pitt, 1989). Output of the
SLAMM model includes, for each rain and land use,
matrices describing source area and outfall flow
volumes, paniculate residue mass and concentrations,
and relative contributions from each rainfall event (Pitt,
1989).
While many other models are also available, some
receive little or no support from their sponsoring parties
and/or have not been widely used. Other widely used
models can simulate hydrology but not pollutant buildup
and washoff. Such models include TR20 (SCS, 1969)
and HEC1 (Hydroiogic Engineering Center, 1990).
These hydroiogic models are not discussed in detail
here; model documentation and references contain the
specific hydroiogic calculations used.
Hydroiogic models, such as TR20 and HEC1, can be
used to generate time-varying runoff flows for one or
more storm events using rainfall and watershed
characteristics as model inputs. To generate urban
runoff pollutant loads, the hydroiogic output (flow versus
time) from the models could be combined with
estimated urban runoff concentrations. For some
applications, for example sizing of BMPs such as
detention ponds, only a hydroiogic model is needed.
Transport Characteristics Determination
In addition to the magnitude of a pollutant load, the
location of a pollution source with respect to the affected
resource, the mode of transport to the resource and
degradation of the pollutant should also be considered.
For example, sources with a clear path to a waterway,
such as pipes, ditches and gulleys, are more likely to
cause adverse effects in a receiving water than similar
sources that must travel through natural filters such as
forested or grassy areas before entering a surface water
body. Changes in loads, from the initial source
discharge to the point where they affect the receptor,
occur because of such factors as travel time, dilution,
soil infiltration, and decay. Fate and transport of
pollutants can be modeled using hydroiogic and
pollutant buildup-washoff models which attempt to
account for these factors deterministically. Since the
simpler methods (i.e., unit load or statistical) can only
empirically estimate these factors, the level of
uncertainty and error is likely to be higher. The level of
uncertainty is high even with the deterministic models,
though. Site-specific data is thus important to validate
any tool which is used.
Resource Assessments
Resource assessments address the impact of pollutant
sources on the resources of interest—taking the results
of the pollutant source assessments (described in the
previous section of this chapter) and determining the
effect of these pollutant sources on water resources.
Assessments, however, can be conducted on other
ecological aspects of a watershed, as well. Water
84
-------
resources can include water quality as well as aquatic
life, sediment, and other characteristics of the water
bodies. Methods to perform resource assessments can
range from evaluation of water quality data and
comparison with criteria, to mathematical modeling of
receiving waters. These methods are described further
in this section.
Basic Data Evaluation
Urban runoff problems can be identified by evaluating
available and newly collected data. Evaluation of
available data is conducted with numerous tools,
including spreadsheets, database management
systems, GIS, statistical analysis (described in Chapter
5), and mathematical models (described in this
chapter). The data are compared to acceptable
resource criteria to determine the existence and severity
of problems.
A useful measure of the condition of a specific water
resource is comparing its water quality, sediment, or
biological data with state water quality standards or EPA
water quality criteria. State water quality standards
define the quality of water that supports a particular
designated use. EPA publishes water quality criteria that
consists of scientific information regarding the
concentrations of specific chemicals in water that
protect species against adverse acute (short-term)
effects on sensitive aquatic organisms, chronic
(long-term) effects on aquatic organisms, and effects on
human health from drinking water and eating fish (U.S.
EPA, 1986). These criteria, often based on results of
toxicity testing of sensitive species, are intended to be
protective of all species. Section 304(a)(1) of the Clean
Water Act requires EPA to publish and periodically
update these criteria.
The Safe Drinking Water Act of 1974, established to
protect public drinking-water supplies, requires EPA to
publish maximum contaminant level goals (MCLGs),
which are non-enforceable levels at which there are no
known or anticipated health effects, and maximum
contaminant levels (MCLs), which are enforceable
levels, based on best technology, treatment techniques,
and other factors including cost. Updates to federal
criteria are announced in Federal Register notices.
States have surface water standards that classify
surface water bodies into use categories, establish
instream levels necessary to support these uses, and
define policies regarding the protection and
enhancement of these water resources. EPA can
establish water quality standards (40 CFR 131) for toxic
pollutants in states and territories that have not fully
adopted their own standards. In addition, many states
have ground-water standards that designate uses for
various ground waters, and water quality levels
necessary to sustain these uses and protect
ground-water quality.
The interpretation of sediment chemistry results is not
straightforward. A number of approaches have been
used to evaluate the degree of contamination in
sediments (Maughan, 1993). Many of these approaches
have been developed to determine impacts associated
with dredging activities (U.S. EPA and U.S. ACOE,
1991). EPA is developing criteria for sediment similar to
those for water quality for certain organic compounds
(U.S. EPA, 1988c). An important factor affecting the
development of these criteria is the bioavailabiiity or
toxicity risk to aquatic organisms due to a contaminant
in undisturbed sediment. Since this bioavailabiiity is
influenced by the physical and chemical nature of the
sediment, toxic effects which might be seen at low
concentrations in some sediment types might not be
evident in others.
To take the variability due to sediment characteristics
into account, contaminant concentrations are
normalized through equilibrium partitioning between
particulate and liquid (pore water) phases, after which
EPA water quality criteria are used to assess
environmental or human health risks. Further
development of sediment criteria for inorganics, such as
metals, is anticipated. Until sediment criteria are
finalized, much of the evaluation of sediment chemistry
data is accomplished on a relative basis by comparing
the results from upstream and downstream stations to
determine if elevated levels of contaminants exist, or by
comparing results to other areas where data are
available.
Ecological effects can be assessed by examining the
biological community structure. Specific parameters to
consider include the relative abundance of pollution-
tolerant and pollution-sensitive species as well as
common indices including, but not limited to,
Shannon-Weiner diversity, Simpson's dominance, and
evenness (Pielou, 1975) as discussed in Chapter 5.
Various types of biological criteria or indices are
available from the literature and can be used for
comparative purposes. An example of the use of
biocriteria to evaluate data is the State of Ohio biotic
index, which has been used to assess the condition of
the biota of rivers and streams since 1978 (U.S. EPA,
1991e). Ohio's use of biocriteria is described in the case
study at the end of this chapter.
Receiving-Water Modeling
Receiving-water models are used to assess existing
conditions and to simulate future conditions of a water
resource under various pollution prevention and control
scenarios. They can also be used to assess the impact
of alternative BMPs (Chapter 8). These models receive
input from runoff model results, field-measured
85
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parameters, and values of parameters found in the
literature. The level of complexity of the receiving-water
model chosen should parallel that of the model used to
assess urban runoff flows and loads. Some commonly
used receiving water models include the Enhanced
Stream Water Quality Model (QUAL2E), the Water
Quality Analysis Simulation Program (WASP4), and the
Exposure Analysis Modeling System II (EXAMSII), as
summarized in Table 6-7 and described in more detail
below. In addition, HSPF, discussed above, has a
receiving-water model component. These models,
along with the SWMM model, are available from
ERA'S Center for Exposure Assessment Modeling,
Environmental Research Laboratory, in Athens, Georgia.
QUAL2E can be used either as a steady-state or
quasi-dynamic model to simulate conditions of rivers
with multiple headwaters, waste discharges, tributaries,
withdrawals, dams, and incremental inflows and
outflows. The model can simulate 15 water quality
constituents, including dissolved oxygen, biochemical
oxygen demand, temperature, nitrogen and phosphorus
species, cdifomns, arbitrary nonconservative constituents,
and conservative constituents (U.S. EPA, 1987c).
QUAL2E-UNCAS is an enhancement to QUAL2E which
allows the user to perform uncertainty analysis on the
effects of model sensitivities and uncertain input data
on model forecasts (U.S. EPA, 1987c). Three types of
uncertainty analyses are available: sensitivity analysis,
first-order error analysis, and Monte Carlo simulation.
Using this model, the user can determine input factors
that contribute the most to the model's uncertainly and
the level of risk associated with model predictions. Both
QUAL2E and QUAL2E-UNCAS are supported by EPA
and are well documented.
The modeling framework of WASP4 provides a
flexible-compartment modeling approach, applicable in
one, two, and three dimensions, which can be used to
simulate contaminant fate in surface water. WASP4 is
structured to allow the easy substitution of user-written
subroutines into the model. Thus, a range of water
quality problems can be simulated by WASP4 using
either one of the model's kinetic subroutines or a
subroutine written by the user. The model can be used
to simulate biochemical oxygen demand, dissolved
oxygen, nutrients and eutrophication, bacterial
contamination, and toxic chemicals in the sediment bed
and in the overlying waters. In addition, WASP4 can be
linked to other models, such as DYNHYD5, a simple
model that simulates variable tidal cycles, wind and
unsteady flows, ^MJhe Food Chain Model, which
predicts pollutant uptake and distribution throughout an
aquatic food chain (U.S. EPA, undated).
EXAMSII performs evaluations and error analyses of
the fate of synthetic organic chemicals based on
user-specified properties of chemicals and ecosystems,
such as descriptions of a system's external loadings,
transport processes and transformation processes.
Model predictions include chemical exposure,
consisting of long-term chronic, 24-hour acute, and
96-hour acute concentrations; fate, consisting of the
distribution of chemicals in the system and the relative
dominance of each transport and transformation
process; and persistence, the time required for effective
purification of the system once the loading has ended
(U.S. EPA, undated).
Model Selection
Selection of receiving water models for resource
assessments (or of urban runoff models for pollutant
source assessments) depends on considerations such
as available input data, project requirements, budget
constraints, and user preference and familiarity. It is
sometimes useful to choose a simple or screening level
model at first to identify major pollutant impacts or loads
for which preliminary control measures could be
implemented. A more complex model can then be
selected if more detailed analyses of the impact of
pollutants and the effect of alternative corrective
measures are required. Since model simulations can
help in selecting pollution prevention and treatment
measures (and thus, in allocating of limited funding), the
user should have experience with the model to ensure
that the model predictions are correct. An understanding
of the selected model and its capabilities and limitations
is critical.
In 1976, EPA compiled a list of questions and factors
that should be considered when selecting a model (U.S.
EPA, 1976b). These considerations, which can be used
to select either urban runoff or receiving water models,
are presented below.
To determine whether a model is required or could be
used, one could consider the following issues:
1. What is the problem to be solved?
2. What temporal resolution is required? Depending on
the type of water quality problem and receiving-
water, single-event, seasonal, or long-term multiple-year
calculations might be appropriate.
3. Is a model needed? If so, what approach is necessary
(e.g., computer program, hand calculations)? Would
a gross assessment of relative loads and impacts
on water quality suffice?
4. What input, calibration, and verification data are
available? The model selected must be calibrated
and verified, and adequate input data must be
collected. If data are not available, or if adequate
funds for data collection are not provided, the use
of a complicated model could be ruled out.
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Table 6-7. Comparison of Receiving-Water Models (U.S. EPA, 1983b, 1985a,b)
Models
Attribute
Application
Dimensionality
State
Water column
transport
Sediment bed
condition
Sediment bed type
Unique features
Enhanced Stream
Water Quality Model
(QUAL2E)
River flow, well-mixed
lakes
One-dimensional
Steady-state
Quasi-dynamic
Advective and dispersive
Completely mixed
Stationary
UNCAS — Uncertainty
analyses of input
parameters on model
forecasts
Water Quality Analysis
Simulation Program (WASP4)
General — river flow, lakes,
estuaries, oceans
Three-dimensional
Time-varying
Advective and dispersive
Completely mixed
Stationary
TOXIC — models dissolved and
adsorbed chemical concentrations
EUTRO4— models DO, CBOD,
nutrients, phytoplankton
DYNHYD5— models tidal cycles,
wind, unsteady inflows
Food Chain model — simulates
uptake and distribution throughout
a food chain
Exposure Analysis
Modeling Systems II
(EXAMS II)
Nontidaf lakes
Three-dimensional
Steady-state
Advective and dispersive
Completely mixed
Simplified exchange
Stationary
Contaminant
transformation and
transport processes
Hydrological
Simulation
Program— Fortran
(HSPF)
Unstratified lakes
One-dimensional
Time-varying
Advective
Completely mixed,
sedimentation
Moving
ARM— Agricultural
runoff model
NFS— Nonpoint
source model
If a model is determined to be necessary, other factors
to consider include the following:
1. Regardless of the method selected, personnel
qualified in water quality analysis should be available.
Any model, simple or complicated, requires a
considerable amount of expert judgment in its
application. Without this expertise, model application
, likely will fail.
2. The major costs in applying any computer-based
model are related to becoming familiar with the
model, collecting basic data for model application
(most of these data remain the same, regardless of
the number of times the model is used), and setting
up the model on the local computer system. Thus,
availability of models that previously have been
calibrated and applied locally should be considered.
Once it has been determined that a model will be used,
the following questions should be considered in
determining whether the model is suitable for the
problem being studied.
1. What, if any, water quality constituents are to be
modeled and can the model accommodate them?
2. Is the problem steady state or dynamic (i.e., do
sources or conditions change over time)?
3. What are the spatial considerations? F:or streams, a
one-dimensional model is adequate if homogeneous
mixing across the river cross-section is an adequate
assumption. For an estuary, a two- or three-
dimensional model might be required.
4. Has a model under consideration been used and
tested? Is good, user-oriented documentation
available?
5. If a proprietary model is considered, how will
continuity in planning be accommodated? The
planning process is ongoing, and models are most
economical when used repeatedly.
6. What are the costs of model application? Computer
costs are relatively insignificant; the major costs of
model use are personnel costs.
Model Validation
The input data file for a model used either for resource
assessment or pollutant source assessment is
calibrated using values of parameters measured during
field investigations of the pollution sources and/or
receiving-water system, depending on the type of
modeling. Parameters to be included as model input,
but that were not measured during field sampling, are
estimated and adjusted to provide a close fit of model
predictions to measured data. Values for parameters not
easily or regularly measured can be obtained from
engineering and scientific publications. Often, typical
values, or "default values," for these parameters are
presented in the model's user manual and can be used
in the initial phases of model calibration.
87
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Model verification, the next step in the model validation
process, often involves using a second data set to verify
the accuracy of the calibrated model input. Measured
parameters from the second data set are input to the
model and simulated levels of parameters (such as
dissolved oxygen concentration) are compared to actual
values measured during the second field sampling
survey. Verification may be conducted qualitatively, by
visually comparing graphical representations of the
model simulation and actual data. In addition, a
quantitative verification can be conducted through the
use of simple statistical comparisons. Calibrated
parameters can be adjusted again, to ensure a good fit
between model predictions and each data set. A
detailed discussion of the model validation procedure
was presented by U.S. EPA (1980).
Once the urban runoff or receiving-water model has
been validated, it can be used to simulate various
scenarios of storm events, pollutant loadings, and
corrective measures. Graphical presentation of model
results is an effective method for displaying model
simulations during evaluation of results and in reports.
While computer modeling is valuable for examining
existing conditions and simulating impacts due to future
changes, users should be aware that model predictions
are only as accurate as the quality of the data used;
some level of error is associated with even the best
modeling techniques.
Institutional Assessments
Assessment of the institutional constraints of a program
provides the managers with perspective concerning the
nontechnical issues affecting the program. The
institutional issues of a program are assessed by
evaluating the program's potential and limitations and
by reviewing the requirements of involved agencies and
the public. One major institutional issue that must be
addressed on an urban runoff program is determining
the responsibilities of each involved party, especially for
programs involving multiple agencies. Issues related to
the control of the program (e.g., enforcement,
maintenance, permitting, and funding) can affect the
program's emphasis and the selection of its corrective
measures. Another institutional issue involves the
limitations of available technology. Implementability of
controls can also be considered, particularly in areas
involving limited access to private properties. The
potential for eliminating or reducing an urban runoff
problem or improving affected water resources can also
be considered. Questions and concerns of the public
might prove to be influential during the decision-making
processes. Applicable regulations could force the
sequencing of corrective measures so that those
addressing compliance with the regulations are
implemented first.
Goals and Objectives Assessments
The relative importance of an urban runoff problem can
be assessed by comparing it to the program's resource
and/or technology-based goals and the objectives of the
program's sponsor, as discussed in Chapter 3. For
example, one water resource goal might be to "provide
improvements to water quality in areas where the most
people will benefit." Comparison of the pollution
problems to such a goal provides the program team with
perspective on which problems to solve to achieve the
goal. By comparing the pollution problems to the
program's goals and objectives, the program team can
identify and focus on problems that are compatible with
these goals. The assessments conducted on pollutant
sources, water resources, and institutional aspects
provide input to these determinations.
Problem Ranking
Since funding to correct pollution problems is usually
limited, the sources or impacts to be addressed should
be prioritized to allow for targeting of limited resources.
While ranking is a subjective process that requires the
judgment of decision-makers, ranking systems can be
used to help develop priorities. A ranking methodology
can range from simple, descriptive methods (qualitative)
to numerically complex (quantitative), depending on
the urban runoff program objectives and funding
constraints. Ranking methods can apply to a variety of
geographic areas, ranging from counties or communities
with multiple watersheds to individual water bodies or
pollution sources. Criteria such as those presented in
Table 6-1 can be used in problem ranking.
Ranking should be conducted following consultation
with involved parties, including local, state, and federal
agencies; local environmental groups; and concerned
citizens. Public opinion can have a large influence on
the ranking of pollution problems. For example, the
public might give priority to controlling sources that
discharge to a favorite pond used for swimming. Urban
runoff control programs should consider public
concerns and desires when prioritizing problems, no
matter which type of ranking approach is employed.
Three types of ranking procedures, ranging from simple
to complex, are discussed in this section.
Qualitative Ranking
The simplest ranking approach uses qualitative
rankings (e.g., high, moderate, or low) to prioritize
pollution problems such as in the example presented in
Table 6-5. Other qualitative ranking methods use letters
(e.g., A, B, C) or numbers (e.g., 1, 2, 3) to develop a
relative scale for comparing problems. The qualitative
rankings must then be interpreted to determine which
problems should be of highest priority in developing
88
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controls. In the example in Table 6-5, the qualitative rank
is based on estimated pollutant load. Other measures
can also be used as a basis for qualitative rankings
{e.g., level of public concern or the importance of the
use to be protected).
Numerical Ranking
To perform numerical ranking, rating points are
assigned to each ranking criterion for each problem.
Each ranking criterion is assigned a weight based on its
importance relative to the other criteria. The rating
points are then multiplied by the relative weight. AH of
the products (i.e., criterion rating x relative weight) are
summed for a given problem. This procedure is then
repeated for all the problems being evaluated. The
sums thus assigned are compared and the problems
with the highest sums receive the highest priority during
implementation of urban runoff controls.
In an example of a numerical ranking system for
prioritizing pollution sources (Woodward-Clyde Consultants,
1990b), a hypothetical application of this weighted
ranking methodology uses the following criteria: water
body importance (as reflected by stream or lake size),
type of use (ranging from urban drainage to recreational
contact), status of use (impaired versus denied), level
of use (low, moderate or high), pollutant loads (not
actual loads but estimates for comparative purposes),
and implementability of controls (based on institutional
factors, existing ordinances, or technical considerations).
These criteria are similar to some identified in Table 6-1.
The relative importance of each criterion is designated
by assigning a weight appropriate for the site-specific
conditions of the watershed under consideration. The
sum of all weights used to rank the problems equals
100. Next, for each problem, the criteria are ranked
using a suggested range of 1 to 9, with a higher
numerical ranking indicating a higher need for corrective
action. This listing allows relative comparisons to be
made among problems with respect to a single criterion.
A hypothetical urban watershed, consisting of three
streams and several types of land use, illustrates this
numerical ranking method for prioritizing pollution
problems (Figure 6-1). Information describing the
system is presented in Tables 6-8 and 6-9. Typical
sources for these data include site-specific pollutant
loading data, model results, and literature values from
data bases such as those identified earlier in,this
chapter. There are four criteria of equal weight: stream
size, beneficial use, pollutant load, and ability to
implement (Table 6-10). The three "use" criteria are
clustered together as subcriteria of the "beneficial use"
criterion.
Ranking for "stream size" is determined based on the
total drainage area of each of the three streams.
Consistent with the goals for the hypothetical
watershed, Stream C is ranked highest with respect to
"type of use" because of its recreational uses in the city
park; because it is used mainly as an urban drain,
Stream B receives the lowest ranking; and Stream A is
ranked between the other two streams because it is
used to support aquatic life. With respect to "status of
use," Stream A ranks highest because although
somewhat impaired, it has the potential to be improved
by control of pollution sources. Stream B receives a low
ranking for use status because its water quality is poor
and its function as part of an urban drainage system has
long been accepted. Stream C also receives a low
ranking for use status since the water is of high quality.
Rankings for "level of use" reflect the number of people
using or affected by each stream.
Mass pollutant loadings are calculated based on runoff
coefficients (functions of the amount of impervious
area), runoff concentrations of pollutants, and the
amount of land use type in each stream's drainage area.
Each stream is ranked based on the proportion of
pollutant load from its watershed (in this example, total
suspended solids is used). The watershed of Stream B
is judged easiest to implement controls because it is
predominantly industrial. Based on the method
presented in this example, Stream C's watershed
should receive priority during implementation of
controls, followed by Stream A's and then Stream B's.
Quantitative Ranking
A fully quantitative ranking of urban runoff problems also
could be performed using pollutant source assessment
methods such as urban runoff models and resource
assessment methods such as receiving-water models.
Quantitative ranking requires the greatest amount of
resources. For this approach, the models would be used
to determine which pollution sources contribute the
greatest impacts by testing various load reduction
scenarios. Through such evaluations, critical problem
sources or impacts could be prioritized. Chapter 8,
which concerns selection of BMPs, discusses this type
of approach further.
89
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Stream C
Open . .^^
(developing)
Stream A
Figure 6-1. Schematic representation of watershed (Woodward-Clyde Consultants, 1990b).
90
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Table 6-8. Characteristics of the Targeted Areas and Estimated Concentration Loads (Woodward-Clyde Consultants, 1990b)
Average Concentration in Runoff, mg/L Drainage Area, ac
Land Use
Category
Industrial
Commercial
Residential (high
density)
Residential (low
density)
Open — developing
Open— urban park
Total urban area
Upstream
drainage area
Total drainage area
Runoff
Coefficient
0.6
0.8
0.4
0.2
0.1
0.1
Total
Suspended
Solids
120
80
90
100
150
50
Oil and
Grease
20
15
10
5
0
0
Total
Petroleum
0.20
0.20
0.40
0.60
0.80
0.80
Copper
0.05
0.05
0.04
0.03
0.01
0.01
Stream
A
0
1°
100
200
0
0
310
600
910
Stream
B
150
80
100
0
0
0
330
0
330
Stream
C
0
110
50
200
150
50
560
20,000
20,560
Urban
Total
150
200
250
400
150
50
1,200
20,600
21,800
Table 6-9. Estimated Total Suspended Solids Loads for Targeted Areas (Woodward-Clyde
Consultants, 1990b]i
Total Suspended Solids, Ib/in of rain
Land Use Category
Industrial
Commercial
Residential (high density)
Residential (low density)
Open — developing
Open — urban park
Watershed total
Watershed rank value
Stream A
0
145
817
908
0
0
1,870
1.7
Stream B
2,452
1,162
817
0
0
0
4,431
4.1
Stream C
0
1,598
409
908
511
57
3,482
3.2
Urban Total
2,452
2,906
2,043
1,816
511
57
9,784
9.0
Table 6-10. Prioritization Analysis for Urban Area Targeting (Woodward-Clyde Consultants, 1990b)
Beneficial Use
Urban Watershed
Weights
Watershed A
Watershed B
Watershed C
Total urban watershed
stream
Size
25
4
2
8
8
Type
10
5
2
8
8
Status
10
7
2
2
5
Level
5
4
1
6
8
pollutant
Load (TSS)
25
1.7
4.1
3.2
9.0
Ability to
Implement
25
5
7
3
2
Target
Score*
100
4.08
3.73
4.85
6.45
* Target score = weighted average of rank points = sum (rank score x weight)/sum (weight)
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Case Study:
Ohio Environmental Protection Agency
Biological Criteria for the Protection of Aquatic Life
Background
Since 1978, the Ohio Environmental Protection Agency (Ohio EPA) has been assessing the biota of
rivers and streams as part of its basic monitoring strategy. This biomonitoring program was developed
for Ohio's fishable waters in response to aquatic life goals of the Clean Water Act. Originally, biocriteria
were used to assess the effects of wastewater treatment plant discharges on aquatic life throughout the
state. Then, with the increased emphasis on addressing storm water runoff and NPS pollution sources,
the Ohio ERA has begun using biomonitoring for these sources.
The use of biocriteria to assess a water body's overall health has several advantages over more common
chemical analysis of receiving waters, including (Ohio EPA, 1987):
• The fish and macroinvertebrates sampled inhabit the receiving water continuously.
• The effects of past events (e.g., floods and droughts) are considered.
• Cumulative impacts can be seen.
• The species used have a long life span.
• The species allow a direct measure of CWA's biological goals.
The traditional approach of water chemistry analysis results in a snapshot of the receiving-water body
at the time of sampling. For a more complete picture, numerous sampling events are required, which
can be very costly. Biocriteria analysis, however, gives a cost-effective assessment, although somewhat
qualitative, of the water body and its ability to support aquatic life.
Analysis Methods
In developing biocriteria, the state was divided into five different ecoregions with generally homogeneous
characteristics. Within each ecoregion, water bodies were selected as "regional reference sites" to
represent "least impacted" conditions. Rather than represent pristine conditions, these sites were
selected based on the amount of stream channel modification, the condition of the vegetative riparian
buffer, water volume, obvious color/odor problems, and general representativeness. Once these sites
were selected, fish and macroinvertebrate sampling programs were implemented to determine water
body characteristics and to obtain information required to develop quantifiable criteria to compare with
the health of othefwatefbodies. Three water Body health indices were developed from the sampling data:
• Index of biotic integrity (IBI)
• Modified index of well being (Mlwb)
• Invertebrate community index
The IBI and Mlwb are used to assess fish community health, and the ICI is used in the assessment of
macroinvertebrate communities. Each index is developed by assessing a number of criteria for the water
body of interest, as described below.
Index of Biotic Integrity
Used as a measure of the health of fish communities, the IBI consists of 12 criteria, or metrics, designed
to give an overall assessment of the biota. The metrics are developed depending on the type of water
resource being analyzed. The three types of sites include headwaters sites (drainage areas less than
20 square miles), wading sites (drainage areas greater than 20 square miles sampled by wading), and
92
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boat sites (drainage areas greater than 20 square miles sampled from a boat). Each of these types has
its own set of metrics for use in determining the IBI, as shown in Table 6-11.
Table 6-11. Index of EJiotic Integrity (IBI) Metrics
IBI Metric
Headwaters
Sites
Wading
Sites
Boat
Sites
1. Total number of'species
2. Number of darter species
Round-bodied suckers, %
3. Number of sunffsh species
Number of headwaters species
4. Number of sucker species
Number of minnow species
5. Number of intolerant species
Number of sensitive species
6. Tolerant species, %
7. Omnivores, %
8. Insectivorous species, %
9. Top carnivores, %
Pioneering species, %
10. Number of individuals
11. Simple lithophils, %
Number of simple lithophilic
species
12. Diseased individuals, %
DELT anomalies, %
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Data for each of these metrics were collected and plotted against drainage area for each of the "least
affected reference sites" in each ecoregion. The plot showing the relationship between the metric and
drainage area was then divided into three equal regions as shown in Figure 6-2. These plots form the
basis for determining the IBI for the water body of concern. When determining the IBI, data for the water
body are compared with the "least affected reference site" plots, and each metric is rated according to
whether it approximates (5), deviates somewhat from (3), or strongly deviates (1) from the value expected
at a reference site. For example, looking at the number of species example shown in Figure 6-2, a water
body with a drainage area of 10 square miles and 10 species collected during a sampling run would be
given a rating of 3 for that metric. Similar ratings are given for all 12 metrics making up the IBI. After all
ratings for a water body are given, they are added up; the sum represents the water body's IBI. Because
of the rating scales used, the IBI for a water body will range from 12 (very poor biotic integrity) to 60
(very good biotic integrity). Ranges of IBI values and their respective qualitative assessments are shown
in Table 6-12.
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I I I I I I II
Wading/headwater sites
10 100
Drainage Area, mi2
1,000
Figure 6-2. Number of species vs. drainage area for determining 5, 3, and 1 Index of blotic Integrity (IBI) scoring.
Table 6-12. Qualitative Assessment of Index of Blotic Integrity (IBI) Values
Wading sites
Boat sites
Headwaters sites
Exceptional
50-60
50-60
50-60
Good
36-48
36-48
40-48
Fair
28-34
26-34
26-38
Poor
18-26
16-24
16-24
Very
Poor
<18
<16
<16
Modified Index of Well Being
The Mtwb is the second index used to describe the quality of fish populations in water bodies throughout
the state. A more traditional index, the Mlwb takes into consideration the fact that healthy systems support
a larger variety and abundance of fish than stressed systems. This index incorporates four measures of
fish community health:
• Numbers of individuals
• Total biomass
• Shannon diversity index based on numbers
• Shannon diversity index based on weight
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The formulas used to calculate Mlwb are:
Mlwb = 0.5 In N + 0.5 In B + H(no.) + H(wt.)
where:
N = relative numbers of all species (excluding species designated highly tolerant)
B = relative weights of all species (excluding species designated highly tolerant)
H(no.) = Shannon diversity index based on numbers
H(wt.), = Shannon diversity index based on weight
The Shannon diversity index is defined by the following formula:
H=-E[(n/N)xln(ni/N)]
where:
nj = relative numbers or weight of the ith species
N = total number or weight of the sample
Ranges of Mlwb values and their respective qualitative assessments are shown in Table 6-13.
Table 6-13. Qualitative Assessment of Modified Index of Well Being (Mlwb) Values
Exceptional Good Fair Poor
Very
Poor
Wading sites
Boat sites
>9.5
8.0-9.3
8.3-9.4
5.9-7.9
6.4-8.7
4.5-5.9
5.0-6.4
<5.0
Invertebrate Community Index
The ICl is used to measure the health of the invertebrate community. Invertebrates are useful as
indicators of environmental quality because they (Ohio EPA, 1987):
• Form permanent and relatively immobile communities
• Can be easily collected in large numbers even in small water bodies
• Can .be sampled at relatively low cost per sample
• React quickly to environmental change
• Occupy all stream habitats
• Inhabit the middle of the aquatic Food web
The method used to determine the ICl is similar to that for the IBI. A number of "least affected reference
sites" were identified and sampled to develop criteria. The ICl consists of 10 invertebrate community
metrics each with four rating categories (0, 2, 4, and 6). The 10 metrics used to calculate the ICl are:
• Total number of taxa
• Total number of mayfly taxa
• Total number of caddisfly taxa
• Total number of dipteran taxa
• Percent mayfly composition
• Percent caddisfly composition
95
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• Percent tribe tanytarsini midge composition
• Percent other dipteran and non-insect composition
• Percent tolerant organisms
• Total number of qualitative EPT taxa [EPT = Ephemeroptera (mayflies), Plecoptera (stoneflies),
Trichoptera (caddisflies)]
The rating involves giving 6 points to sites of exceptional quality, 4 points for those representing typical
good communities, 2 points for slightly affected communities, and 0 points for highly affected
communities. As shown in Figure 6-3, plots have been developed to determine the range of values for
each metric. For example, a stream sample that has a drainage area of 100 square miles and a total of
30 taxa would receive a rating of 4. A similar analysis is performed for each metric and the 10 values
are summed to obtain the final ICI value. This value, which ranges from 0 to 60, represents the health
of the water body with respect to the invertebrate community. Ranges of ICI values and their respective
qualitative assessments are shown in Table 6-14.
60
50
40
30
20
10
I
10
100
Drainage Area, mi2
1,000
10,000
Figure 6-3. Total taxa vs. drainage area for determining 6, 4, 2, and 0 invertebrate community Index (ICI) scoring.
Table 6-14. Qualitative Assessment of Invertebrate Community Index (ICI) Values
Exceptional Good Fair Poor
Very
Poor
All sites
48-60
34-46
14-32
2-12
Example of Biocriteria Implementation
Taken from the upper Hocking River in Ohio, the calculation of IBI values for fish habitat at two different
river headwater stations are shown in Table 6-15. In this example, the fish habitat at Station 2 is
significantly better than at Station 1. As indicated by Table 6-12, the index for Station 1 (14) ranks it as
very poor for fish habitat, while the rating for Station 2 (34) ranks it as fair for fish habitat. In order to
96
-------
compare these habitats effectively, strict controls had to be kept over the
fish and analyze the results. To implement similar programs in other areas
studies and tests must be conducted because of the site-specific nature of
the IBI.
Table 6-15. Indices of Biotic
Integrity for Two Headwater
methods used to obtain the
, the necessary background
the criteria used to develop
Stations in Hocking River, Ohio
Station 1
Numbers of
Total species
Total individuals
Sunfish species
Sucker species
Intolerant species
Proportion of individuals, %
Round-bodied suckers
Omnivores
Insectivores
Tolerant species
Top carnivores
Simple lithophils
Anomalies
Totals
Value
5
12
1
1
0
0
67
19
(36
7
7
0
Ranking
1
1
1
1
1
1
1
1
1
3
1
1 .
14
Station
Value
14
130
4
3
0
34
38
50
42
10
57
0
2
Ranking
3
1
5
3
1
3
1
3
1
3
5
5
34
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
Driscoll, E.D, RE. Shelley, and E.W. Strecker. 1989.
Pollutant loadings and impacts from highway storm
water runoff. McLean, VA: Federal Highway
Administration, Office of Engineering and Highway
Operations Research and Development.
Driver, N.E., and G.D. Tasker. 1990. Techniques for
estimation of storm-runoff loads, volumes, and
selected constituent concentrations in urban
watersheds in the United States. Denver, CO: U.S.
Geological Survey. Open-File Report 88-191, Water
Supply Paper #2363.
Hydrologic Engineering Center. 1990. HEC1, flood
hydrograph package user's manual. U.S. Army Corps
of Engineers.
Maughan, J.T. 1993. Ecological assessment of
hazardous waste sites; chapter 7, evaluation of
contaminants in sediments. New York, NY: Van
Nostrand Reinhold.
Metcalf & Eddy, Inc. 1991. Wastewater engineering:
treatment, disposal, and reuse, 3rd edition. New York,
NY: McGraw-Hill.
Novotny, Vladimir. 1992. Unit pollutant loads. Water
Environ. Tech. January.
Nix, Stephan. 1991. Applying urban runoff models.
Water Environ. Tech. 3(6).
Ohio EPA. 1987. Ohio Environmental Protection Agency.
Biological criteria for the protection of aquatic life.
Division of Water Quality Monitoring and Assessment.
97
-------
Pielou, E.C. 1975. Ecological diversity. New York, NY:
John Wiley & Sons.
Pitt, Robert. 1989. SLAMM 5—source loading and
management model: an urban nonpoint source water
quality model, volume I: model development and
summary. University of Alabama at Birmingham.
SOS. 1969. Soil Conservation Service. Project
formulation program: hydrology. Tech. release no. 20.
U.S. Department of Agriculture.
SCS. 1977. Soil Conservation Service. Procedure for
computing sheet and rill erosion on project areas.
Tech. release no. 51. U.S. Department of Agriculture.
Tasker, G.D., and N.E. Driver. 1988. Nationwide
regression models for predicting urban runoff water
quality at unmonitored sites. Water Res. Bull.
24(5):1091-1101.
U.S. EPA. 1974. U.S. Environmental Protection Agency.
Urban stormwater management and technology: an
assessment EPA/670/2-74/040 (NTIS PB-240687).
December.
U.S. EPA. 1976a. U.S. Environmental Protection
Agency. Storm water management model: level
I—preliminary screening procedures. EPA 600/2-76/275
(NTIS PB-259916). October.
U.S. EPA. 1976b. U.S. Environmental Protection
Agency. Areawide assessment procedures manual,
volumes I, II and III. EPA/600/9-76/014 (NTIS
PB-271863). U.S. EPA Office of Research and
Development. July.
U.S. EPA. 1977. U.S. Environmental Protection Agency.
Urban stormwater management and technology:
update and users' guide. EPA/600/8-77/014 (NTIS
PB-275654). Washington, DC. September.
U.S. EPA. 1979. U.S. Environmental Protection Agency.
A statistical method for the assessment of urban
stormwater. EPA/440/3-79/023 (NTIS PB-299185/a).
U.S. EPA. 1980. U.S. Environmental Protection Agency.
Measures of verification. Proc. Workshop on
Verification of Water Quality Models. EPA/600/9-80/
016 (NTIS PB80-186539). April.
U.S. EPA. 1981. U.S. Environmental Protection Agency.
User's manual for hydrologic simulation program-
Fortran (HSPF). Release 7.0. Washington, DC.
U.S. EPA. 1982a. U.S. Environmental Protection
Agency. Urban rainfall-runoff-quality data base.
EPA/600/S2-81/238. July.
U.S. EPA. 1982b. U.S. Environmental Protection
Agency. Water quality assessment: a screening
procedure for toxic and conventional pollutants,
volumes I and II. EPA/600/6-82/004a (NTIS
PB83-153122) and b (NTIS PB83-153130).
U.S. EPA. 1983a. U.S. Environmental Protection
Agency. Results of the Nationwide Urban Runoff
Program, volume 1. Final report. Washington, DC:
, U.S. EPA Water Planning Division. (NTIS
PB84-185552.)
U.S. EPA. 1983b. U.S. Environmental Protection
Agency. Technical support manual: waterbody
surveys and assessments for conducting use
attainability analyses, volumes I, II and III. Office of
Water Regulations and Standards. Washington, DC.
November.
. U.S. EPA. 1985a. U.S. Environmental Protection
Agency. Technical guidance manual for performing
wasteload allocations. Washington, DC. May.
U.S. EPA. 1985b. U.S. Environmental Protection
Agency. Rates, constants, and kinetics formulations
in surface water quality modeling, 2nd ed.
EPA/600/3-85/040 (NTIS PB85-245314). June.
U.S. EPA. 1986 as updated in 1987. U.S.
Environmental Protection Agency. Quality criteria for
• water. EPA/440/5-86/001.
U.S. EPA. 1987a. U.S. Environmental Protection
Agency. Setting priorities: the key to nonpoint source
control. Office of Water Regulations and Standards.
Washington, DC.
U.S. EPA. 1987b. U.S. Environmental Protection
Agency. Guide to nonpoint source pollution control.
Office of Water. Washington, DC.
U.S. EPA. 1987c. U.S. Environmental Protection
Agency. The enhanced stream water quality models
QUAL2E and QUAL2E-UNCAS: documentation and
user model. EPA/600/3-87/007 (NTIS PB87-202156).
U.S. EPA. 1988a. U.S. Environmental Protection
Agency. Ready reference guide to nonpoint source
pollution; sources, pollutants, impairments; best
management practices for the New England states.
Detailed from U.S. Department of Agriculture, Soil
Conservation Service. U.S. EPA Region I. Boston, MA.
U.S. EPA. 1988b. U.S. Environmental Protection
Agency. Storm water management model, version
4.0: user's manual. Washington, DC.
98
-------
U.S. EPA. 1988c. U.S. Environmental Protection
Agency. Interim sediment criteria values of nonpolar
hydrophobic organic contaminants. Washington, DC:
U.S. EPA Office of Water Regulations and Standards,
Criteria and Standards Division. SCO #17.
U.S. EPA. 1990. U.S. Environmental Protection Agency.
Assessment of urban and industrial stormwater runoff
toxicity and the evaluation/development of treatment
for runoff toxicity abatement—phase I. Edison, NJ.
U.S. EPA Office of Research and Development.
U.S. EPA. 1991 a. U.S. Environmental Protection
Agency. Water quality problem identification in urban
watersheds. Seminar publication, Nonpoint Source
Watershed Workshop. EPA/625/4-91/027 (NTIS
PB92-137504).
U.S. EPA. 1991b. U.S. Environmental Protection
Agency. Guidance for water quality-based decisions:
the TMDL process. EPA 440/4-91/001. April.
U.S. EPA. 1991c. U.S. Environmental Protection
Agency. Evaluation of dredged material proposed for
ocean disposal: testing manual. EPA/503/8-91/001.
U.S. EPA. 1991d. U.S. Environmental Protection
Agency. Modeling of nonpoint source water quality in
urban and non-urban areas. EPA/600/3-91/039 (NTIS
PB92-109115). U.S. EPA Office of Research and
Development.
U.S. EPA. 1991e. U.S. Environmental Protection
Agency. The use of biocriteria in the assessment of
nonpoint and habitat impacts in warmwater streams.
Proc. Nonpoint Source Watershed Workshop.
EPA/625/4-91/027 (NTIS PB92-137504).
U.S. EPA. 1992. U.S. Environmental Protection Agency.
Casco Bay storm water management project:
Concord Gully, Frost Gully and Kelsey Brook
watersheds. U.S. EPA Region I. Boston, MA. January.
U.S. EPA. Undated. U.S. Environmental Protection
Agency. Description of the services and models
available from the Center for Exposure Assessment
Modeling (CEAM), Office of Research and
Development, Environmental Research Laboratory.
Athens, GA.
U.S. EPA and U.S. ACOE. 1991. U.S. Environmental
Protection Agency and U.S. Army Corps of
Engineers. Evaluation of dredged material proposed
for ocean disposal: testing manual. EPA/503/
8-91/001.
Walesh, S.G. 1989. Urban surface water management.
New York, NY: John Wiley & Sons, Inc.
Woodward-Clyde Consultants. 1990a. Pollutant loading
and impacts from highway stormwater runoff,
volumes 1 through 4. McLean, VA: Federal Highway
Administration.
Woodward-Clyde Consultants. 1990b. Urban targeting
and BMP selection: an information and guidance
manual for state NPS program staff engineers and
managers. Final report.
99
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Chapter 7
Screen Best Management Practices
Selecting BMPs for preventing and controlling urban
runoff pollution is a two-step process. First, a
comprehensive list of BMPs should be compiled and
screened to eliminate those that are inappropriate for
the area. Based on appropriate BMPs, alternatives are
then developed and assessed. Finally, the BMPs to be
implemented are selected.
This chapter addresses the first step in this process—
initial screening. First, a general overview of the
categories of BMPs addressed in this handbook is
given. The chapter then describes methods of
screening the list of potential BMPs. The remainder of
the chapter defines BMPs used for urban runoff
pollution prevention and control, along with a brief
description of their characteristics and sources of
additional information. This chapter's contents assist in
compiling a list of BMPs for consideration in the
screening process.
Best Management Practice Overview
Urban runoff pollution problems are more difficult to
control than steady-state, dry-weather point source
discharges because of the intermittent nature of rainfall
and runoff, the number of diffuse discharge points, the
large variety of pollutant source types, and the variable
nature of the source loadings. Since the expense of
constructing facilities to collect and treat urban runoff is
often prohibitive, the emphasis of storm water pollution
control should be on developing a least cost approach
which includes nonstructural controls and low-cost
structural controls.
Nonstructural controls include regulatory controls that
prevent pollution problems by controlling land
development and land use. They also include source
controls that reduce pollutant buildup or lessen its
availability for washoff during rainfall. A case study at
the end of this chapter discusses the extensive
nonstructural regulatory urban runoff controls used by
Austin, Texas.
Low-cost structural controls include the use of facilities
that encourage uptake of pollutants by vegetation,
settling, or filtering. Because of the variability of
pollutant removal, these controls can be used in
series or in parallel combinations. The concept of
implementing a "treatment train" might, for example,
include initial pretreatment, primary pollutant removal,
and final effluent polishing practices to be constructed
in series.
All sources, both point and nonpoint, in a program area
or watershed should be addressed. For urban areas,
such sources often include urban runoff as well as
CSOs. Practices for controlling both storm water and
CSO pollution are described in this chapter. The
practices discussed for urban runoff control are also
applicable to storm water before it enters a combined
sewer collection system. In addition, this chapter
describes various types of storage and treatment
facilities also commonly used to address CSOs.
Depending on the pollutant control mechanisms used,
urban runoff pollution control practices can be divided
into several categories:
• Regulatory controls
• Source controls
• Detention facilities
• Infiltration facilities
• Vegetative practices
• Filtration practices
• Water quality inlets
CSO-specific control practices are also divided into
several categories:
• Source controls
• Collection system controls
• Storage
• Physical treatment
• Chemical precipitation
• Disinfection
While these lists do not include all urban runoff and
CSO control practices, these categories are convenient
ones for purposes of presentation and discussion.
101
-------
Table 7-1 lists commonly used urban runoff and CSO
BMPs based on the categories provided. The next
section describes methods of BMP screening. The
remainder of the chapter then gives a brief overview of
some of the more important characteristics of these
BMPs, including the types of pollutants controlled, the
pollution removal mechanisms employed, limitations on
their use, maintenance requirements, and general
design considerations.
Best Management Practice Screening
The goal of BMP screening is to reduce the
comprehensive list of BMPs to a more manageable list
for final selection. Because this step is an initial
screening, methods used are generally qualitative and
require professional judgment. While extensive
knowledge about specific design criteria is not
necessary at this stage in the screening process,
Table 7-1. Urban Runoff Pollution Control BMPs
Urban Runoff Controls
Regulatory Controls
Land uso regulations
Comprehensive runoff control regulations
Land acquisition
Source Controls
Cross-connection Identification and removal
Proper construction activities
Street sweeping
Catch basin cleaning
Industrial/commercial runoff control
Solid waste management
Animal waste removal
Toxic and hazardous pollution prevention
Reduced fertilizer, pesticide, and herbicide use
Reduced roadway sanding and salting
Detention Facilities
Extended detention dry ponds
Wet ponds
Constructed wetlands
Infiltration Facilities
Infiltration basins
Infiltration trenches/dry wells
Porous pavement
Vogctatlva Practices
Grassed swales
Filter strips
Filtration Practices
Filtration basins
Sand fillers
Other
Water quality inlets
understanding the BMP's effectiveness and applicability
to the program area's problems is crucial.
For this discussion, the BMPs are divided into two
general categories: nonstructural and structural.
Nonstructural BMPs—which include regulatory
practices, such as those that limit impervious area or
protect natural resources, and source controls, such as
street sweeping or solid waste management—are
typically implemented throughout an entire community,
watershed, or special area. While structural BMPs, such
as detention ponds or infiltration practices, may be
designed to address specific pollutants from known
sources, they also can be implemented throughout an
area. In addition, structural BMPs can be required in
new developments or redevelopments.
Comprehensive plans addressing urban runoff pollution
prevention and control rely on both nonstructural and
structural practices. While plans addressing specific
CSO Controls
Source Controls
Water conservation programs
Pretreatment programs
Collection System Controls
Sewer separation
Infiltration control
Inflow control
Regulator and system maintenance
Insystem modifications
Sewer flushing
Storage
Inline storage
Offline storage
Flow balance method
Physical Treatment
Bar racks and screens
Swirl concentrators/vortex solids separators
Dissolved air flotation
Fine screens and microstrainers
Filtration
Chemical Precipitation
Biological Treatment
Disinfection
Chlorine treatment
UV radiation
102
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problems in small watersheds might tend to focus on
structural practices, urban runoff pollution prevention
and control programs should include implementation of
nonstructural as well as structural control approaches.
Methods for screening both nonstructural and structural
practices are outlined below.
Nonstructural Practices
Since the number of potential nonstructural BMPs to be
implemented is very large, initial screening is useful
before the final selection process. The regulatory and
source control BMP descriptions contained later in this
chapter focus on the most commonly implemented
practices; other, less commonly used practices,
however, also could be considered. In addition, each
practice (e.gi, solid waste management) can be divided
into numerous subpractices (e.g., management of leaf
litter, rubbish, garbage, and lawn clippings). An urban
runoff management plan for the Santa Clara Valley, for
example, identified more than 100 separate potential
nonstructural BMPs used throughout the country
(Woodward-Clyde Consultants, 1989). Municipalities,
therefore, have to screen regulatory and source control
BMPs based on their particular watershed. The Santa
Clara Valley program and the BMP screening and
selection method are discussed in the case study at the
end of Chapter 8.
One screening method involves applying screening
criteria to each nonstructural practice to determine its
applicability to the conditions in the watershed. The
screening criteria, which are specific to the watershed
and depend on the program goals, include:
• Pollutant removal: Since different regulations and
source control practices are designed to address
different pollutants, the program team should ensure
that the screened list of controls includes practices
designed to address the pollutants of primary
concern. In addition, some practices might not
provide sufficient pollutant removal.
• Existing government structure: Some practices
implemented throughout the country require a
specific government structure. For example, while a
strong county government might be important for
implementing a specific regulatory control, the role of
county governments can vary from one section of the
country to another. Practices requiring specific
government structures that do not exist in the area
of concern therefore could be eliminated from the list.
• Legal authority: For regulatory controls to be
effective, the legal authority to implement and enforce
the regulations must exist, if municipal boards and
officials lack this authority, they could be required to
obtain it through local action.
• Public or municipal acceptance: Implementing certain
practices could be difficult because of resistance from
the public or an involved municipal agency. These
practices can be eliminated from the list.
• Technical feasibility: The municipal BMPs that require
large expenditures and extensive efforts might not be
suitable for small municipalities that lack the required
resources.
Additional screening criteria may also be used, as
shown in the Santa Clara Valley case study at the end
of Chapter 8.
Another method of screening involves use of a
comparative summary matrix. Figure 7-1 shows an
example of such a matrix that can be used to screen
nonstructural control practices. Though developed for
screening nonstructural control practices in coastal
areas, this matrix is at least in part applicable to inland
areas as well. In this matrix, various regulatory and
source control practices are listed and their abilities to
meet various criteria are compared. The criteria listed
include ability to remove specific pollutants, such as
nutrients and sediments, maintenance requirements,
longevity, community acceptance, secondary environmental
impacts, costs, and site requirements. Other criteria are
also listed, some of which are applicable only in coastal
areas. For each practice and criterion, an assessment
of effectiveness is indicated: solid circles indicate high
effectiveness and open circles, low effectiveness. This
type of matrix can provide a basis for an initial
assessment of practices and their applicability to the
program.
Structural Practices
Because structural practices generally are more site
specific and have more restrictions on their use than
nonstructural practices, the initial screening step for
these practices can be more precise than for
nonstructural practices. Table 7-2 outlines some of the
more important criteria for the screening of structural
BMPs, including their typical pollutant removal
efficiencies, land requirements, the drainage area that
each BMP can effectively treat, the desired soil
conditions, and the desired ground-water elevation. By
using these criteria and the information obtained during
data collection and analysis and problem identification
and ranking, the program team can narrow the list of
BMPs to be further assessed in the BMP selection step.
The initial screening criteria for structural control
practices include the following:
• Pollutant removal: The municipality should ensure
that BMPs selected address the primary pollutants of
concern to the level of removal desired.
103
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Table 7-2. Structural BMP Initial Screening Criteria
Structural BMPs
Detention Facilities
Extended detention
dry ponds
Wat ponds
Constructed wetlands
Infiltration Facilities
Infiltration basins
Infiltration
trenches/dry wells
Porous pavement
Vegetative Practices
Grassed swales
FHtor strips
Filtration Practices
Filtration basins
Sand filters
Other
Water quality Inlets
Suspended
Solids
Medium
Medium-
high
Medium-
high
Medium-
high
Medium-
high
High
Medium
Medium-
t^t «
high
Medium-
high
High
Low-
medium
Typical
Nitrogen
•
Low-
medium
Medium
Low
Medium-
high
Medium-
high
High
Low-
medium
Medium-
high
Low
Low-
medium
Low
Pollutant Removals3
Phosphorus
Low-medium
Medium
Low-medium
Medium-high
Low-medium
Medium
Low-medium
Medium-high
Medium-high
Low
Low
Pathogens
Low
Low
Low
High
High
High
Low
Low
Low
Low
Low
Metals
Low-
medium
Medium-
high
Medium-
high
Medium-
high
Medium-
high
High
Low-
medium
Medium
Medium-
high
Medium-
high
Low
Relative
Land
Require-
ments
Large
Large
Large
Large
Small
N/A
Small
Varies
Large
Varies
N/A
Drainage
Area"
Medium-
large
Medium-
large
Large
Small-
medium
Small
Small-
medium
Small
Small
Medium-
large
Low-
medium
Small
Desired
Soil
Conditions
Permeable
Impermeable
Impermeable
Permeable
Permeable
Permeable
Permeable
Depends
on type
Permeable
Depends
on type
N/A
Ground-
Water
Elevation
Below
facility
Near
surface
Near
surface
Below
facility
Below
facility
Below
facility
Below
facility
Depends
on type
Below
facility
Depends
on type
N/A
. tawn — -*ww/Qt iviouiuui — wwu/o, i iiyu = t»
Small» <10 acres, Medium = 10-40 acres, Large = >40 acres.
• Land requirements: Large land requirements for
some of the aboveground structural BMPs can often
restrict their use in highly developed urban areas.
Land requirements vary depending on the BMP.
* Drainage area: The structural BMPs listed in Table
7-2 are used primarily to treat runoff from watersheds
up to 50 or 60 acres, and the optimum drainage area
to be served varies for each practice and according
to the land use (connected impervious area, for
example). Drainage areas above this size might have
to be treated by locating BMPs in subwatersheds.
• Soil characteristics: Structural BMPs have differing
requirements for soil conditions. Infiltration facilities
generally require permeable soils, while detention
BMPs generally require impermeable soils. The
municipality must become familiar with soil conditions
in the watershed.
• Ground-water elevation: The ground-water elevation
in the watershed can be a limiting factor in siting and
implementing structural BMPs. Generally, high
ground-water elevation can restrict the use of
infiltration facilities and filtration practices; but it is
necessary for constructed wetlands and may be
desirable for detention facilities.
• Public acceptance: Since a municipality could have
difficulty implementing a structural BMP without
public approval, public acceptance of the BMPs
should be considered in the screening step.
Of the screening criteria listed, the pollutant removal,
land requirements, and drainage area served are
usually absolute restrictions. Soil condition and
ground-water elevation, on the other hand, impose
restrictions that could be overcome by such means as
importing soil or constructing facilities with clay liners to
106
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restrict ground-water inflow. Such modifications,
however, can add significantly to the BMP costs.
Best Management Practice Descriptions
This section provides a brief overview of the BMPs
discussed, based on the categories presented in Table
7-1. Additional references should be consulted before
selecting, designing, and implementing BMPs (see
Appendix A). Appendix B lists widely available and
helpful documents that provide more detailed
information on designing, constructing, and maintaining
urban runoff and CSO BMPs. There are a host of other
BMPs that address specific pollution sources, such as
landfills, industrial sites, salt storage facilities, marinas,
and numerous others. As mentioned earlier, agricultural
BMPs are not discussed in depth in this handbook.
Urban Runoff Control Practices
This section addresses regulatory controls, source
controls, and several types of commonly used structural
controls.
Regulatory Controls
Urbanization increases the amount of impervious land
area, which in turn increases storm water runoff with its
associated pollutants (see Chapter 1). Municipalities
can prevent or reduce many of these pollution problems
by implementing regulatory controls to limit the amount
of impervious area and to protect valuable resources.
These regulatory controls can prevent or limit the
quantity of runoff as well as its pollution load. Regulatory
controls typically implemented by municipalities include:
• Land use regulations, such as:
- zoning ordinances,
- subdivision regulations,
- site plan review procedures, and
— natural resource protection.
• Comprehensive runoff control regulations.
• Land acquisition.
Local government regulations can require storm runoff
controls, reduce the level of impervious area, require
the preservation of natural features, reduce erosion, or
require other important practices. The major aspects of
storm water prevention and control—including runoff
quantity control, solids control, and other pollution
control—are illustrated in the case study at the end of
this chapter on the regulatory practices implemented by
Austin, Texas.
Runoff Quantity Control. Regulations addressing
runoff quantity control can be used to reduce the
effects of land development on watershed hydrology.
Hydrologic control in turn results in pollution contra/,
and can be accomplished through requirements such as:
• Open space: By maintaining specified levels of open
space on a development site, the total area of
impervious surface is reduced and infiltration of
precipitation is increased. This leads to decreases in
total pollutant discharge and potential downstream
erosion by reducing total and peak runoff flows.
• Postdevelopment flow control: Many development
regulations require that peak runoff conditions from
a site be calculated before and after construction.
These requirements specify that conditions after
construction must reflect conditions before
construction. This control is typically accomplished
through the use of detention facilities, which can
reduce peak runoff discharge rates, thereby
decreasing downstream erosion problems. These
regulations specify the desired outcome; the
approach for ensuring that outcome, however, is
determined by the developer.
• Runoff recharge: Regulations may specify that storm
water runoff be recharged on site. Such regulations
can reduce the runoff leaving a site, thereby reducing
development-induced hydrologic changes and
pollutant transport. By directly promoting infiltration,
peak and total runoff rates can be decreased and
pollutant discharges and downstream erosion can be
reduced. Such runoff recharge also might help
maintain surficial aquifer levels.
Solids Control. Regulations addressing solids control
could include requirements for control practices during
and after construction, since such activity has been
shown to be a major contributor of solids. Construction
activities can greatly increase the level of suspended
solids in storm water runoff by removing vegetation
and exposing the topsoil to erosion during wet
weather. Yet while communities have requirements for
implementing erosion control practices on construction
sites, fewer communities require erosion control after
construction is complete. Since many other land uses
can contribute solids loadings, regulatory requirements
can cover various types of industrial and commercial
activities.
Other Pollution Control. Land development increases
the concentrations of nutrients, pathogens, oxygen
demanding substances, toxic contaminants, and salt
in storm water runoff. Development regulations,
therefore, can be used to address some of these
specific pollutants. These regulations can take the form
of special requirements for limiting nutrient export in
special protection districts or setting performance
standards for known problem pollutants.
While many of the regulatory controls outlined in this
section are used by municipalities, few communities
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have used these regulations systematically to prevent
urban runoff pollution problems. The regulations, developed
over a number of years, have had purposes largely
unrelated to urban runoff pollution prevention and
control. By reexamining and amending these regulations
and ordinances to reflect water resource goals, however,
communities can improve their ability to prevent and
control urban runoff pollution.
Land Use Regulations. Land use regulations can
include zoning ordinances, subdivision and site plan
regulations and review requirements, and environmental
resource regulations such as wetlands protection.
These practices are used as tools to promote
development patterns that are compatible with control
of urban runoff discharges.
Zoning, Most communities have residential, commercial,
industrial, and other zoning districts that specify the
types of development allowed and dictate requirements,
including:
• Specifying the density and type of development
allowed in a given area, thereby maintaining pervious
areas.
• Controlling acreage requirements for certain land
uses and associated setback, buffer, and lot
coverage requirements.
• Directly and indirectly affecting the types of materials
that can be stored or used on sites.
• Not allowing potentially damaging uses (e.g.,
underground chemical storage or pesticide application)
in sensitive watersheds.
Examples of types of zoning controls that can be used
to protect water bodies include:
• C/asfercfeve/opme/tf: Allowing structures in developments
to be constructed close together to preserve open
space.
• Down-zoning: Changing an established zone to a use
that allows a lower level of density.
* Phase-in zoning: Changing the zoning of a specific
area over time, usually as inappropriate sites reach
the end of their useful life.
• Large lot zoning: Requiring greater minimum acreage
for development in certain locations.
• Conditional zoning: Allowing certain activities only
under specified conditions that protect water quality.
• Overlay zoning: Placing additional zoning requirements
on an area that is already zoned for a specific activity
or use.
• Open space preservation: Protecting open space and
buffer zones in the community near water bodies.
• Performance standards: Permitting certain land uses,
usually industrial activities, only if they meet specific
performance criteria.
These practices can be used by communities to ensure
that land uses in each area are appropriate for that
area's water resources. Such controls are especially
useful in sensitive areas, such as water supply
watersheds, and can serve to reduce or control
development.
Subdivision Regulations. Subdivision review deals with
land that is divided into separately owned parcels for
residential development. Municipalities have the
authority to review the plans for such subdivisions and
to restrict development options via requirements for
drainage, grading, and erosion control, as well as
provisions for buffer areas, open spaces, and
maintenance. Through this review, municipalities can
ensure that proper practices are designed into the
development.
Site Plan Review. Site plan review ensures compliance
with zoning, environmental, health, and safety
requirements. Municipalities can require developers to
consider how construction activities will affect drainage
on site and to design plans for reducing urban runoff
pollution problems. Developers usually are required to
submit information to a municipality on the natural
drainage characteristics of the site, plans for erosion
control, retention and protection of wetlands and water
resources, arid disposal of construction-related wastes.
Natural Resource Protection. Municipalities can also
protect water resources by protecting lands, such as
floodplains, wetlands, stream buffers, steep slopes, and
wellhead areas. By use of resource overlay zones that
restrict high pollution activities in these areas,
development can be controlled and the potential for
urban runoff pollution can be reduced.
Comprehensive Runoff Control Regulations. In
addition to strengthening and broadening existing local
regulatory control practices, states and municipalities
can implement runoff pollution control through
comprehensive regulations. While still relatively rare,
comprehensive plans to address urban runoff pollution
exist in various states and communities. They are
designed to fully address urban runoff pollution
problems by identifying specific land use categories
and water resources that deserve special attention,
and outlining methods for implementing source control
and structural BMPs. While the form that these
comprehensive regulations take is very specific to the
needs of a state or community, reviewing the
regulatory approaches that have been tried by others is
useful in developing options. Examples include (Pitt,
1989):
108
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• Austin, TX: Comprehensive Watersheds Ordinance,
1986; Urban Watersheds Ordinance, 1991 (see the
case study at the end of this chapter).
• Birmingham, AL: Proposed Watershed Protection
Ordinance.
• State of Maryland: Model Stormwater Management
Ordinance, 1988.
• State of Wisconsin: Model Construction Site Erosion
Control Ordinance, 1987.
Land Acquisition. To protect valuable resources from
the effects of development, municipalities can purchase
land within the watershed to control land development.
Municipalities can acquire land to convert to parks or to
maintain as open space; this approach, however, can
be very expensive.
Source Control Practices
Source controls include the nonstructural practices
designed to reduce the availability of pollutants. Many
of these practices tie directly into EPA's Pollution
Prevention strategy discussed in Chapter 2, which
focuses on preventing pollution sources from entering
the system rather than on treatment. Some of the more
common practices used by municipalities throughout
the country include:
• Cross-connection identification and removal
• Proper construction activities
• Street sweeping and catch basin cleaning
•' Industrial/commercial runoff control
• Solid waste management
• Animal waste removal
• Toxic and hazardous waste management
• Reduced fertilizer, pesticide, and herbicide use
• Reduced roadway sanding and salting
Cross-Connection Identification and Removal.
Within the NPDES storm water regulations, EPA has
specifically emphasized the importance of implementing
a program to identify and remove inappropriate sanitary
and industrial wastewater connections to municipal storm
water drainage systems—a problem in many urban
areas. For example, a study of the storm drainage
system in the Humber River watershed in Toronto
indicated that about 10 percent of the outfalls from
the system had dry-weather flows considered to be
significant pollutant sources. This study found that
more than 50 percent of the annual discharges of
water volume, total suspended solids, chlorides, and
bacteria from the monitored industrial, residential and
commercial areas were associated with dry-weather
discharges from the storm drainage system (U.S. EPA,
1993a). .
Dry-weather discharges, such as from illegal wastewater
discharges to the storm drainage system, can cause
serious water resource degradation. The addition of
sanitary wastes increases the concentrations of
organics, solids, nutrients, and bacteria in the storm
water runoff. Industrial wastes can be highly variable but
can substantially increase the concentrations of heavy
metals and other related pollutants in runoff (U.S. EPA,
1993a).
Unauthorized and inappropriate connections to drainage
systems can exist for many reasons. In the past,
connector pipes between sanitary sewers and storm
drains could have been installed to relieve surcharging
of the sewer system and prevent backups of sewage
into homes and businesses. Connections from residential
sanitary sewers or commercial and industrial floor
drains also exist. '
Cross-connections are common in municipalities that
have undergone sewer separation. During separation,
a new pipe system is often constructed to act as a
separate sanitary sewer, and the old combined system
is converted to operate as a separate storm drain
because of its large size and carrying capacity. To
complete the separation, existing connections to the
combined sewer must be plugged and reconnected to
the new sanitary sewer. If sewer connections to the
newly created storm drain continue to exist with no
written record or are not located on plans, they can be
missed during the reconnection. In addition, as new
construction occurs, accidental connections to the
storm drainage system can occur.
Because cross-connections typically are not documented,
pollution from these connections can often be difficult to
locate. Municipalities, however, can develop a program
to locate and eliminate these connections. This program
should be designed to identify dry-weather discharges
and to determine the flow sources by developing
updated drainage system maps, conducting dry-
weather inspections, and sampling dry-weather
discharges. In some instances, discharge results from
ground-water infiltration to the drainage system and
might not be a pollution concern. If the analyses
conducted on dry-weather flows indicate the presence
of pollutants, however, the system should be traced to
locate the source of the pollutants.
Locating cross-connections to storm drainage systems
is similar to conducting the infiltration and inflow (I/I) and
sanitary sewer evaluation survey (SSES) investigations
that many municipalities regularly conduct. These
investigations can be done through successive visual
inspections, dye testing, or TV investigations. Once
located, cross-connections must be removed so that
109
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Industrial and sanitary wastes are discharged to a
municipal sewerage system. Routine drainage system
inspections should continue in order to avoid problems
from inadvertent cross-connections from new development.
Detailed information is available in an EPA guidance
document entitled Investigation of Inappropriate Pollution
Entries Into Storm Drainage Systems (U.S. EPA,
1993a).
Proper Construction Activities. Construction activities
have been cited in numerous water quality assessments
as a major source of sediment to surface waters.
During construction, natural vegetation is removed
from a site, exposing the topsoil. If the soil remains
bare and exposed for extended periods, rainfall can
cause erosion and transport the soil to nearby water
bodies. After the soil enters a water body, decreases in
water velocity cause the suspended solids to settle out
of the water column and accumulate as sediment on
the bottom of the water body. This sediment can
smother benthic organisms and carry pollutants, such
as petroleum products and metals. Construction-
induced erosion therefore should be minimized. This
section addresses some of the planning practices and
controls that can be used at construction sites to
reduce erosion and subsequent soil transport.
While the practices discussed in this section are general
and can be applied at construction sites throughout the
country, most state environmental offices have
developed soil and erosion control handbooks tailored
to the specific needs of the state. These documents
provide more detailed guidance for developing and
implementing programs to address construction site
pollution problems. In addition, some municipalities,
such as Birmingham, Alabama (Pitt, 1989), have
developed ordinances to address construction-site
erosion controls.
On construction sites, areas to be maintained in their
preconstruction condition should remain undisturbed
during construction; existing vegetation to be
incorporated into the final site should be maintained.
The planned roads and parking areas should be used
for construction traffic and other construction-related
activities; these areas can be treated with crushed stone
during construction and paved after construction has
been completed. Planned open areas at a site should
be seeded immediately after clearing, and open areas
not in use for construction should be covered with
crushed stone or seeded with a temporary cover crop.
The planning, sequencing, and timing of construction
activities are also important to reduce soil transport.
Phasing and limiting of clearing activities so that one
area of a site is complete and stabilized before
beginning work on other areas can also reduce the
potential for erosion.
On large construction sites with extensive grading and
vegetation removal, structural erosion control practices
are required. During construction activities, temporary
berms or weirs can divert runoff away from disturbed
areas of the site. Runoff diversion or slope modifications
should be incorporated into the final site design; during
construction, these diversion structures should be
protected by crushed stone or blankets to reduce
erosion.
Since construction site runoff contains high levels of
suspended solids, temporary structures that filter out or
settle out solids should be incorporated into the site.
Straw bales, silt fences, dewatering filters, and
sedimentation basins are often used to control erosion.
Straw bales can be placed across a sloped area to
intercept runoff from the slope and trap sediment. They
can also be used around storm water inlets and catch
basins to reduce the transport of sediment to nearby
drainage systems. In addition, straw bales can be
placed at intervals along long slopes to reduce runoff
velocity to control erosion. Straw bales need to be
replaced every few months; the old bales can be broken
up and used for ground cover if properly installed and
maintained. Silt fences can be used for many of the
same functions as straw bales and usually have a
longer life.
In addition to these temporary, inexpensive erosion-
control devices, storm water runoff from larger
construction sites should be directed to sedimentation
basins, designed to intercept runoff and hold it for an
extended period to allow suspended solids to settle out.
Sedimentation basins, which require periodic cleaning,
already might be incorporated into the final site design
as permanent storm water attenuation/treatment
controls. When construction is completed, they should'
be cleaned out and the bottoms regraded.
To ensure that construction site erosion control
practices are properly implemented and that regulations
are followed, plans must be reviewed prior to
construction activities and inspections must be
conducted. Municipalities or responsible agencies must
provide for erosion control plan review, site review, and
enforcement.
Street Sweeping and Catch Basin Cleaning.
Frequent street sweeping can limit the accumulation of
dirt, debris, and associated pollutants, and the
subsequent deposition of these pollutants in storm
drains and waterways. Regular cleaning of catch
basins can also remove accumulated sediment and
debris that ultimately could be discharged from storm
drains and combined sewers. In most municipalities,
these tasks are conducted at scheduled intervals and
have been shown to result in significant pollutant
reductions only if an intensive schedule is followed. A
study performed in San Jose, California, showed that
110
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50 percent of the total solids and heavy metals could
be removed from urban runoff when city streets were
cleaned once or twice a day. When the streets were
cleaned only once or twice a month, the removal rate
dropped to less than 5 percent (U.S. EPA, 1979).
Increased frequency also could result in increased
fugitive air emissions. Regular street sweeping and
catch basin Cleaning can, in any case, remove some of
the large floatable litter that is unsightly in urban
surface waters. Street sweeping twice a week and
catch basin cleaning once or twice a year have been
found effective in removing these large floatable
pollutants (U.S. EPA, 1983). Determining the effectiveness
of street sweeping programs, however, is difficult
because of variations in pollutant buildup and storm
events. In addition, studies have shown that the choice
of sweeping equipment can significantly affect the
effectiveness of cleaning programs (Pitt, 1989).
Commercial/Industrial Runoff Control. Certain
commercial and industrial sites can be responsible for
disproportionate contributions of some pollutants (e.g.,
grit, oils, grease, and toxic materials) to the drainage
system. Typical sources of potential concern include
gasoline stations, railroad yards, freight loading areas,
and parking lots. In specific cases where significant
pollutant loadings to the system are contributed by
well-defined locations of limited area, pretreatment of
the runoff from these areas could be a practical and
effective control measure. Pretreatment measures can
be required as part of a community's regulations.
Examples of pretreatment measures include oil/water
separators for gasoline stations, or the use of modified
catch basin designs to enhance the retention of oil and
grease or solids. Procedures for the detection and
location of illicit connections to separate storm drains
by testing for specific chemical tracers could be applied
to identify commercial or industrial sources contributing
substantial levels of problem pollutants.
Solid Waste Management. Most communities have
programs to collect and dispose of solid waste in an
effort to maintain clean streets and provide a service
for local residents and businesses. Some communities
provide added services during times otparticularly high
waste generation. For example, some municipalities in
the northern United States provide extra collection
services during the fall to collect leaves—an added
service that helps keep leaves from blowing into
surface waters. A study of storm water runoff into
Minneapolis lakes found that phosphorus levels were
reduced by 30 to 40 percent when street gutters were
kept free of leaves and lawn clippings (MPCA, 1989).
Actual reductions of pollutant loads, however, are
difficult to predict. In general, any solid waste that is
picked up and disposed of in a controlled manner will
be less likely to enter a drainage system.
Animal Waste Removal. Domesticated and wild
animal wastes represent a source of bacteria and other
pollutants that can be washed into surface waters by
urban runoff. These pollutants can be reduced by
reducing the animal waste on paved surfaces.
Municipalities often enact and enforce leash laws and
pet waste cleanup ordinances. The effectiveness of
these programs in reducing pollutant loads is unknown,
however, and usually depends on voluntary actions by
private citizens.
Toxic and Hazardous Waste Management. Improper
dumping of household and automotive toxic and
hazardous wastes into municipal storm inlets, catch
basins, and other storm drainage system entry points
can result in significant discharges of pollutants to
surface waters during rainstorms. This dumping can be
a particular problem in urban areas where individuals
change the oil or antifreeze in their cars and dispose of
the wastes in nearby catch basins. In addition,
homeowners and small businesses sometimes dispose
of products such as waste paints and solvents in storm
water inlets and catch basins. To address the problem,
municipalities can educate residents on the
consequences of dumping these wastes into storm
drainage system entry points. In addition, communities
can develop hazardous- and toxic-waste collection
days to dispose of or recycle these wastes properly.
Also, storm drain systems can be labeled with
warnings about the pollution prcolems associated with
dumping wastes. The effectiveness of such programs,
however, cannot be determined in advance because of
the voluntary nature of compliance. For business and
industry, an inspection, testing, and enforcement
program (similar to an industrial pretreatment program)
can be developed.
Reduced Fertilizer, Pesticide, and Herbicide Use.
Fertilizers, pesticides, and herbicides washed off the
ground during storms can contribute to water pollution.
Agricultural, park land, and other land uses can be
sources of these pollutants. Many communities use
these chemicals on park lands, and homeowners
utilize them on their lawns. Controlling the use of these
chemicals on municipal lands and educating the public
can help reduce nutrient and toxic pollutant
concentrations in urban runoff.
Reduced Roadway Sanding and Salting. In areas of
the United States with freezing road conditions, sand
and salt are used in the winter to improve driving
conditions. Salt and sand can be washed off roadways,
however, and pollute receiving waters. The problem is
exacerbated during spring snowmelt and early spring
rainstorms when most of these pollutants are available
for transport. These problems can be reduced by
minimizing the use of chemicals for snow and ice
control to the minimum necessary for public safety and
111
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by utilizing proper equipment. In addition, salt storage
sites have been shown to be persistent and frequent
sources of contamination, especially during rainfall
(U.S. EPA, 1973); sand and salt piles therefore should
be covered. Also, deicing alternatives, such as calcium
magnesium acetate (CMA), can be used in some
cases (U.S. EPA, 1974a,b).
Detention Facilities
One of the most common structural methods for
controlling urban runoff and reducing pollution loading
is through the construction of ponds or wetlands to
collect runoff, detain it, and release it to receiving waters
in a controlled manner. Pollution reduction during the
perfod of temporary runoff storage results primarily from
settling of solids. Detention facilities, therefore, are most
effective at reducing the concentrations of solids and
the pollutants that typically adhere to solids, and less
effective at removing dissolved pollutants.
Currently, the three types of detention facilities
commonly used to remove pollutants from storm water
runoff are extended detention dry ponds, wet ponds,
and constructed wetlands; each is discussed below. For
more detailed design information, the references listed
in Appendix B should be consulted.
Extended Detention Dry Ponds. Most municipalities
are familiar with the concept of constructing dry ponds
to control peak runoff. When used as water quality
BMPs, dry ponds are designed with orifices or other
structures that restrict the velocity and volume of the
discharges (see Figure 7-2). Dry ponds thereby detain
the runoff before discharging it to surface waters.
Pollutant Removal. During the storage period, heavier
particles settle out of the runoff, removing suspended
solids and pollutants, such as metals, that attach to the
particles or precipitate out. Some dry ponds also include
vegetated areas that can provide pollutant removal
through filtering and vegetative uptake. Dry ponds are,
therefore, most effective at removing suspended solids
and some nutrients and metals, and less effective at
removing dissolved pollutants and microorganisms.
Overall, the pollutant removal effectiveness of dry
ponds has been shown to be less than for wet ponds
and constructed wetlands (see Table 7-2). ,
Design Considerations. Retrofitting existing dry ponds
with new outlet structures can sometimes enhance a
municipal flood-control structure to increase its pollution
control effectiveness. Care must be taken, however, to
ensure that the overflow capacity of the pond is
maintained, so that it continues to fulfill its original
flood-control function. Study of the hydraulic
characteristics of the dry pond will be necessary before
retrofitting. Temporary storage also can be provided for
runoff from smaller storms by building a small berm
around an existing outlet structure.
For water quality dry ponds, important design criteria
include the desired detention time and the volume of
runoff to be detained. These factors dictate the pond's
size and affect the pollutant removal efficiency of the
structures. Most dry-pond sizing criteria specify a
Maximum
elevation
of extended
detention pool
Safety
bench
Emergency spillway
r\
Maintenance access
to micropool
FIgur* 7-2. Extended detention pond (U.S. EPA, 1991 a).
112
-------
certain detention time for a given design storm. For
example, the Maryland Water Resources Authority
specifies that water quality dry ponds must be large
enough to accommodate the runoff volume generated
by the 1-year, 24-hour storm to be released over a
minimum of 24 hours (Schueler, 1987). In contrast, the
Washington State Department of Ecology (WA DOE)
specifies that dry ponds must be large enough to
accommodate the runoff volume generated by the
2-year, 24-hour storm and release it over a period of 40
hours (WA DOE, 1991).
Dry ponds should also include some form of low-flow
channel designed to reduce erosion; vegetation on the
bottom of the pond to promote filtering, sedimentation,
and uptake of pollutants; and an outlet structure
designed to remove pollutants and withstand clogging.
In addition, dry pond designs typically include upstream
structures to remove coarse sediments and reduce
sedimentation and clogging of the outlet. Also, outlets
might be connected to grassed swales (biofilters) to
provide additional pollutant removal (WA DOE, 1991).
Each of these components of a dry pond design either
enhances pollutant removal or reduces operation and
maintenance costs for the structure.
Maintenance Requirements. Maintenance of water
quality dry ponds is important. Regular mowing,
inspection, erosion control, and debris and litter
removal, are necessary to prevent significant sediment
buildup and vegetative overgrowth (Schueler, 1987).
Also, periodic nuisance and pest control could be
required. Dry-pond design should recognize these
maintenance requirements. The pond slopes should
allow for mowing, and access roads should be provided.
Limitations on Use. Like other storm water treatment
structures used in large watersheds, a primary physical
constraint on the construction of water quality dry ponds
is their large land requirements. For this reason,
locating dry ponds in new developments is usually more
practical than constructing them in already developed
areas. Other physical constraints include the
topography and the depth to bedrock.
Wet Ponds. The design of wet ponds is similar to that
of dry ponds and constructed wetlands. In wet ponds,
storm water runoff is directed into an constructed pond
or enhanced natural pond, in which a permanent pool
of water is maintained until being replaced with runoff
as shown in Figure 7-3. Once the capacity of a wet
pond is exceeded, collected runoff is discharged
through an outlet structure or an emergency spillway.
Pollutant Removal. The primary pollutant removal
mechanism in wet ponds is settling. The ponds are
designed to collect storm water runoff during rainfall and
to detain it until additional storm water enters the pond
and displaces it. While the runoff is detained, settling of
particulates and associated pollutants takes place in the
pond. ,
Wet ponds can also remove pollutants from runoff
through vegetative uptake. Wet ponds should be
vegetated with native emergent aquatic plant species,
which can remove dissolved pollutants such as
nutrients from the runoff before it is discharged to the
receiving water.
Design Considerations. Wet ponds typically are
designed with a number of different water levels. One
level of the pond has a permanent pool of water. The
next level periodically is inundated with water during
storms; this area should be vegetated and relatively flat
to promote settling and filtering of sediments and
vegetative uptake of nutrients. The highest level will be
inundated only during extremely heavy rainfall; this area
also should be vegetated to prevent soil erosion. At
least 30 percent of the surface area of a wet pond
should be a vegetated zone (Livingston et aL, 1988).
Typically, this vegetation is concentrated at the outlet as
a final "polishing" biofilter.
The sizing of wet ponds is similar to that of dry ponds
in that a number of different "sizing rules" provide
varying levels of pollution control. Generally, these rules
specify the volume of runoff to be detained in the Wet
pond during a storm. For example, the Maryland Water
Resources Authority specifies that the permanent pool
of a wet pond should be large enough to contain
one-half inch of runoff distributed over the impervious
portion of the contributing watershed (MD WRA, 1986).
In Florida, storage volume for 1 inch of runoff above the
normal pool elevation is recommended. This volume
must be released at a slow rate; no more than half
should be discharged within 60 hours after the event,
and all the volume must be released after 120 hours. A
hydraulic retention time of 14 days for the permanent
pool volume is recommended (Livingston et al., 1988).
The design of water quality wet ponds must also take
into consideration the possibility of large storms.
Emergency spillways should be included in the design
to prevent flooding difficulties. In addition, the pond's
inlet and outlet structures should be separated and
constructed at either end of the pond to maximize full
mixing when large flows occur and avoid short-
circuiting. By separating the inlet from the outlet, the
detention time of the pond can also be increased. A
forebay or other system for pretreatment also might be
advisable. Further design guidelines for wet ponds can
be found in the references in Appendix B.
Maintenance Requirements. Like many other BMPs,
wet ponds require routine maintenance to be effective.
Wet ponds are designed to allow for settling of
suspended solids; therefore, periodic removal of the
accumulated sediment must be performed (perhaps
113
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Cross Section
Top of embankment
Max. safety storm WSE
imergenoy spillway Inverted
Riser crest
Safety storm passage
2-yr storm water management storage
Extended detention (ED) storage
%£%%#^^
£>^^
Note: Figure not to scale.
Antiseep collars
Plan View
- Max. safety storm water surface elevation (WSE)
Max. extended
detention (ED) WSE
r— wax. saieiy storm water sunace elevation (wst)
X. J^"' /—Max 2-yr stormWSE_ *'—
"
Embankment
"
Riser in
embankment
Outlet
protected
by riprap
' "«^T^: Max. ED WSE—^ £^ /
"""* -.*> Max". 2-yr storm WSE- - " J$\
---_ . * <£•£**
-
Emergency
spillway
Max. safety storm WSE
Figure 7-3. Wet detention system (Roesner et al., 1988).
114
-------
every 10 to 20 years). Removed sediment must be
disposed of in accordance with appropriate regulations,
which could include testing and special handling
requirements for contaminated material. In addition, the
pond slopes should be regularly mowed to make the
sediment removal process easier and to enhance the
aesthetic qualities of the area. Inlet and outlet structures
should be inspected periodically for damage and
accumulated litter, and the pond bottom should be
inspected for potential erosion. Erosion of the pond
bottom from high velocity flows can result in increased
sediment transport and overall reduction in the pollutant
removal capabilities of the pond.
Limitations on Use. Water quality wet ponds have large
land requirements and usually are more suited to new
development projects where they can be designed into
the site. In addition, wet ponds are not suitable for use
in areas with porous soils or low ground-water levels
because a pool of water in the bottom is key to their
design. Wet ponds should be built into the ground water
with their control elevation set above the level of
seasonal high water tables. Synthetic impermeable
materials or clay can be used to prevent seepage. Wet
ponds also have physical limitations related to the site
topography; since locating wet ponds in areas with
extreme slopes is often difficult, relatively flat locations
are preferable.
Constructed Wetlands. Constructed wetlands are
effective in removing many urban storm water
pollutants. Two prevalent types of systems are
shallow-constructed wetlands (Figure 7-4) and wet
detention systems (Figure 7-5). The wet detention
system is a wet pond with extensive shoreline shallow
wetland areas. Wetland systems combine the pollutant
removal capabilities of structural storm water controls
with the flood attenuation provided by natural wetlands.
Proper design of constructed wetlands—including their
configuration, proper use of pretreatment techniques to
remove sediments and petroleum products, and choice
of vegetation—is crucial to the functioning of the
system.
Pollutant Removal. Constructed wetland systems
perform a series of pollutant removal mechanisms
including sedimentation, filtration, adsorption, microbial
Inflow
Level spreader
mechanism
Outflow
Figure 7-4. Example shallow-constructed wetland system design for storm water treatment (Maryland DNR, 1987).
Outflow
Sediment sump
Oil/grease
skimmer
(10:1 desirable;
4:1 minimum)
Deeper area
Figure 7-5. Example wet detention system design for storm water treatment (Livingston et at., 1988).
115
-------
decomposition, and vegetative uptake to remove
sediment, nutrients, oil and grease, bacteria, and
metals. Wetland systems reduce runoff velocity, thereby
promoting settling of suspended solids. Plant uptake
accounts for removal of dissolved constituents. In
addition, plant material can serve as an effective filter
medium, and denitrification in the wetland can remove
nitrogen. A review of pollutant removal effectiveness
data for 15 constructed wetlands and 11 natural wetland
systems designed to treat storm water found high
removals of total suspended solids and lead and only
fair removal of ammonia, total phosphorus, and zinc
(U.S. EPA, 1992a). In addition, constructed wetlands
were found to have higher average removal rates and
less variability than natural systems (U.S. EPA, 1992a).
Specific wetland vegetation species remove specific
pollutants from storm water runoff (RIDEM, 1989).
Some of the most commonly used wetland vegetation
includes cattails, bulrushes, and canary grass.
Design Considerations. Because the use of wetland
systems for storm water runoff control is a relatively new
technology, generally accepted design criteria do not
exist. Some general guidelines, however, are
recognized as important in the design of wetland
systems. These guidelines include maximizing the
detention time of runoff in the wetland system,
maximizing the distance between the inlet and outlet,
and providing some form of pretreatment for sediment
removal.
Maximizing the travel time of runoff through a wetland
system allows for greater opportunity for sediments to
settle out of the water and for wetland plants to take
up nutrients and other pollutants. Travel time can be
increased in a wetland by reducing the gradient over
which the flow travels or by making the flow travel
over a greater distance before being discharged. In
either case, some designers recommend a 24-hour
detention time during the 1-year, 24-hour storm
(RIDEM, 1989). if the distance separating the inlet
from the outlet in a wetland system is not sufficient,
flow might enter the wetland system and not become
fully mixed during large rainstorms (see also the wet
pond discussion). This phenomenon, known as
short-circuiting, can greatly reduce the wetland
system's level of treatment. Short-circuiting can be
reduced by careful design of the wetland system.
Wetland design should also take into account that
sediment accumulation in wetland systems can
greatly shorten their effective life and that some
suspended solids should be removed from the runoff
before it enters the wetland system. The design
should include sloped sides to allow easy removal of
accumulated sediments and harvesting of plants.
Recommendations for constructed wetland systems
are expected to evolve as more research is
conducted.
Maintenance Requirements. Like most storm water
quality controls, constructed wetlands require regular
maintenance. In addition to regularly scheduled
sediment removal, wetland systems should be
periodically cleared of dead vegetation. Harvesting of
plants in the wetland might be appropriate for pollutant
removal purposes; if so, disposal of removed material
must be planned.
Limitations on Use. While constructed wetland systems
can treat storm water runoff effectively, they do require
large areas of undeveloped land, which can make siting
of wetland systems difficult especially in urban areas.
For this reason, incorporating wetland systems into new
development is usually more feasible than retrofitting
them into existing developments. Existing wetlands
occasionally can be retrofitted for pollutant removal if
not prohibited by local or state regulations. Achieving
proper soil conditions and ground-water levels can also
present difficulties. To maintain a wetland environment,
soils must be resistant to infiltration (i.e., have low
permeability) and a water supply must be constant. In
general, soils in the system must be saturated
throughout the growing season so the desired
vegetation will survive. Since natural wetlands are
protected resources, diverting storm water to them for
treatment will likely be prohibited. Finally, created
wetlands become a resource area that may be subject
to protection under federal, state, and local laws.
Infiltration Facilities
Unlike detention facilities that capture and eventually
release storm water runoff to a surface water body,
infiltration facilities permanently capture runoff so that it
soaks into the ground water. Because they do not
release the runoff to a surface water, infiltration facilities
are sometimes called retention facilities. Pollutant
removal in these BMPs occurs primarily through
infiltration, which eliminates the runoff volume or lowers
it by the capacity of the facility. Since the infiltrated flow
can travel through the ground water and still be released
to surface waters, dissolved pollutants such as some
nutrients and metals could be reintroduced to the
surface water with minimal pollutant removal. Currently,
the three different types of facilities commonly used to
promote infiltration and remove pollutants from storm
water runoff are infiltration basins, infiltration
trenches/dry wells, and porous pavement (grassed
swales, which also promote infiltration, are addressed
later under vegetative practices). Each of these BMPs
is discussed in this section. For detailed design
information, the references listed in Appendix B should
be consulted.
Infiltration Basins. Infiltration basins are similar to dry
ponds, except that infiltration basins have only an
emergency spillway and no standard outlet structure.
116
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All flow entering an infiltration basin (up to the capacity
of the basin) is, therefore, retained and allowed to
infiltrate into the soil (see Figure 7-6).
Pollutant Removal. Infiltration is the major pollutant
removal mechanism. Infiltration basins, like dry and wet
ponds, receive storm water runoff from drainage
systems and provide storage up to a designed volume.
Unlike dry detention ponds which eventually release
stored runoff through a drainage system, or wet ponds
which maintain a permanent pool of water, infiltration
basins release stored runoff through the basin's
underlying soil. Infiltration basins provide storm water
pollutant removal through volume reduction and
filtration and settling. Infiltration basins are particularly
effective in removing bacteria, suspended solids,
insoluble nutrients, oil and grease, and floating wastes.
They are less effective in removing dissolved nutrients,
some toxic pollutants, and chlorides. Therefore
infiltration basins should not be used when the
ground-water quality itself is a concern or when these
pollutants can be reintroduced through ground-water
flow to surface waters.
Design Considerations. The most important consideration
in the design of infiltration basins is calculating the
basin's size for the drainage area and the soil type
involved. Some designers recommend off-line basins to
capture and infiltrate the first one-half inch of rainfall
from the contributing drainage area (MD WRA, 1986).
The appropriate amount of flow must be diverted to the
system, and soil tests need to be performed to estimate
the infiltration rates and appropriately size the basin.
Also related to the proper size of infiltration basins is the
amount of time necessary for the basin bottom to dry
between rainstorms. Designers generally specify that
infiltration basins should be designed to be dry for at
least 3 days between storms (Schueler, 1987). This
interval allows the soil to dry, thereby increasing its
pollutant removal capacity. Basin shape is also
important. It should have gently sloping sides to allow
for easy access to mow the bottom vegetation. An
emergency spillway must also be incorporated into the
basin design. Finally, some form of pretreatment is
recommended to remove suspended sediments from
runoff before it is discharged to the basin. This
pretreatment will reduce the need for periodic removal
of accumulated sediment which can clog the soil pores
and reduce the level of infiltration.
Maintenance Requirements. Infiltration basins require
moderate to high levels of periodic maintenance. Most
are designed with vegetated bottoms to provide
stabilization and promote some vegetative uptake of
nutrients. Periodically, the bottom of the basin must be
mowed and accumulated sediments must be removed
to maintain desired infiltration rates.
Limitations on Use. Infiltration basins often have
relatively large land requirements and are better suited
for location in developing areas than in already
developed areas. Infiltration basins also require suitable
soil to be effective. Accumulating runoff must be able to
infiltrate the soil in the bottom of the basin. Typically,
sand and loam, with infiltration rates greater than or
equal to 0.27 in/hr (WA DOE, 1991), are the preferred
soils for infiltration systems. The use of infiltration
basins can be restricted by high ground-water
elevations. For infiltration to occur, ground-water levels
should be located at least 2 to 4 feet below the bottom
of the basin.
Top view
Riprap
outfall
protection
Riprap
settling
basin and '*
level spreader
Flat basin floor with
dense grass turf
Figure 7-6. Sample infiltration basin.
117
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Infiltration Trenches/Dry Wells. Subsurface infiltration
practices, such as infiltration trenches or dry wells,
force runoff into the soil to recharge ground water and
remove pollutants. These infiltration structures are
located below ground and usually must be built "off
line" because of their limited storage area (see Figure
7-7). Subsurface infiltration systems generally consist
of precast concrete structures with holes in the sides
and bottom surrounded by 2 to 4 feet of washed stone.
Storm water runoff is directed into these structures and
infiltration takes place.
Pollutant Removal. The structural controls described in
this section use filtration as the primary pollutant
removal mechanism, much like onsite wastewater
treatment systems commonly used in many small
communities. These controls effectively remove
suspended sediments and floating debris, as well as
bacteria which are difficult to remove without
disinfection. Infiltration practices are generally less
effective at removing dissolved nutrients, such as
nitrogen or other soluble contaminants, which can travel
through ground water and be discharged to the
receiving water.
Design Considerations. The soil infiltration rate is
probably the most important consideration in the design
of infiltration structures. The soils underlying the
structure must be tested to determine their suitability for
infiltration. Some authorities specify the types of soils
acceptable for infiltration as noted above for infiltration
basins. Structure size is another primary consideration.
The structures must be large enough to handle the
desired design storms. Also, the structures must be
designed to allow larger storms to bypass them.
Because subsurface infiltration structures do not have
outlets, they usually have to be designed off line of the
regular drainage system. Runoff can then enter the
infiltration structure until it is full; additional runoff is
directed away from the structure. A diversion structure
upstream of the infiltration structure is normally part of
the design. The flow entering this structure (which could
be a simple manhole) is directed to the subsurface
infiltration structure until it is full; then additional flow is
directed away from the structure and along the drainage
system. A typical sizing rule for subsurface infiltration
structures is they should store the runoff from the first
one-half inch of rainfall on the site (Livingston et al.,
1988).
Infiltration structures must also be designed to empty in
a reasonable length of time. The underlying soils, to
remove pollutants from runoff effectively, must be
allowed to dry between rainstorms. Most experts specify
that infiltration structures should contain a reservoir of
runoff for no more than 3 days after rainfall (Shaver,
1986).
Maintenance Requirements. Infiltration structures require
periodic cleaning to remove accumulated sediment and
petroleum products. Often the need for this maintenance
can be reduced by incorporating into the design a
pretreatment structure that removes sediments and
petroleum products from the runoff. These pretreatment
Dike
20 ft minimum vegetated strip
Filter fabric
Aggregate
3 ft minimum
depth
Filter fabric
Rguro 7-7. Sample infiltration trench (Livingston et al., 1988).
118
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structures can also minimize the discharge to ground
water of some pollutants, such as solids. While
addressing these issues in the design of infiltration
structures can reduce routine maintenance requirements,
the design still should include an observation well that
allows inspectors to determine sediment deposition.
Limitations on Use. Subsurface infiltration structures
can be used for end-of-pipe treatment as well as be
located at different points in the drainage system. If
located at the downstream end of a drainage system,
infiltration structures can have large land requirements.
Subsurface infiltration structures, because they are
located underground, can be located in areas such as
parking lots and access roads.
The primary physical limitation to locating infiltration
structures, other than land requirements, is the
suitability of soil, which must be neither too
impermeable to runoff (e.g., clay, silt, or till) nor too
rapidly permeated (e.g., sand). Another potential
physical limitation is the depth to ground water. To
provide proper treatment and reduce the possibility of
ground-water contamination, a distance of at least 2 feet
should be maintained between the bottom of the
infiltration structure and the mean high ground-water
elevation.
Porous Pavement. Paved roads and parking areas,
because they increase watershed imperviousness, are
major contributors to storm water runoff problems in
urban areas. Porous pavement, however, allows water
to flow through a porous asphalt layer and into an
underground gravel bed. Porous concrete pavement
can also be used. Use of this porous pavement can
thereby reduce runoff volume and pollutant discharge.
This practice, used in areas with gentle slopes, is
generally designed into parking areas that receive light
vehicle traffic.
Pollutant Removal. Field studies have shown that
porous pavement systems can remove significant levels
of both soluble and paniculate pollutants (Schueler,
1987). Porous pavement is primarily designed to
remove pollutants deposited from the atmosphere, as
coarse solids can clog the pavement pores. In these
systems, pollutant removal occurs primarily after the
runoff has infiltrated into the underlying soils. Pollutant
removal is accomplished by trapping of sediments, and
infiltration through the underlying soils which can
remove pollutants such as bacteria. The removal
efficiency depends on the storage volume of the
pavement, the basin surface area, and the soil
percolation rate (U.S. EPA, 1991b).
Design Considerations. Porous asphalt pavement
generally is designed with an upper pavement layer 2-
to 4-inches thick, a 1- to 2-inch layer of coarse sand, a
stone reservoir to provide storage, and a bottom filter
fabric as shown in Figure 7-8. Other types of porous
pavement include poured-in-place concrete slabs,
pre-cast concrete grids, and modular units of brick or
cast concrete (Livingston et al., 1988). The differences
in pavement design result in different ways that the
collected runoff is discharged. Some systems let all the
runoff discharge through the underlying soils and into
im
Porous asphalt: Coarse asphaltic
mix (1/2- to 3/4-in aggregate)
in a layer that is 21/2 to 4 in thick.
Filter: Coarse (i.e., 1/2-in)
aggregate in a layer that is
2 in thick.
Reservoir: Coarse (i.e., 1- to 2-in)
aggregate; voids are designed for
runoff detention. Thickness of layer
depends on storage required
and frost penetration.
' Filter fabric
Existing soil: Minimal compaction,
so that porosity and permeability
are retained.
Figure 7-8. Porous pavement cross section (WA DOE, 1991).
119
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the ground water. While these systems provide good
pollutant removal, they can result in ground-water
contamination. Other systems include perforated pipes
to collect the runoff and discharge it directly to a surface
water; while these systems protect the ground water
below the pavement, they do not provide the same level
of pollution removal as the full infiltration systems.
Porous pavement is designed so that a certain amount
of runoff is collected and stored in the stone reservoir.
The design criteria, therefore, determines the depth of
the stone reservoir. The maximum depth of the stone
reservoir also is affected by the infiltration rate of the
underlying soils. Runoff should be completely drained
within a maximum of 3 days after the maximum design
storm event to allow the underlying soils to dry,
maintaining aerobic conditions that improve pollutant
removal (Schueler, 1987).
Maintenance Requirements. Porous pavement can
have extensive maintenance requirements. The
pavement must be kept free of coarse particles that can
clog the pavement and prevent runoff from collecting.
The pavement must, therefore, be regularly inspected
and cleaned with a vacuum sweeper and high pressure
jet The state of Maryland, by reviewing its porous
pavement practices, found that after 4 years of use only
two of the 13 systems were functioning as designed
(Lindsey etal., 1991). The 11 malfunctioning sites were
affected primarily by clogging and excessive sediment
and debris.
Limitations on Use. Because porous pavement is
expensive to replace or repair, it is generally only used
on parking areas that receive moderate to low traffic.
The area to be paved also should be relatively flat with
a depth of 2 to 4 feet from the bottom of the stone
reservoir to the high water table. In addition, the soils
under the pavement must allow for infiltration.
Vegetative Practices
Urbanization results in the elimination of vegetation and
increases in impervious area. Vegetative practices in
urban areas decrease the impervious area and promote
runoff infiltration and solids capture. These practices
generally provide moderate to low pollutant removal and
are therefore used as pretreatment for the removal of
suspended solids from runoff prior to more intensive
treatment by other practices. The two major types of
vegetative practices commonly used in urban areas are
grassed swales and filter strips (both sometimes
referred to as biofliters). Native vegetation is
recommended since it requires less site preparation and
maintenance.
Grassed Swales. Grassed swales are channels
covered with vegetation to reduce erosion of soil during
storms (see Figure 7-9). They are used to replace
conventional catch basin and pipe network systems for
transporting runoff to surface waters. Storm water
runoff flows through the grassed swale reducing runoff
velocity and promoting the removal of suspended
solids.
Pollutant Removal. Infiltration of the runoff and
associated pollutants is the most important pollutant
removal process accomplished by grassed swales.
Grassed swales also remove pollutants through filtering
by the vegetation and settling of solids in low-flow areas.
Because of these pollutant removal mechanisms,
swales are most effective at removing suspended solids
and associated pollutants, such as metals. The
mechanism of infiltration also allows removal of bacteria.
Erosion control
seed mix or sod —,
Trapezoidal Cross Section
Minimum
freeboard
Channel bottom
sloped for proper
flow conveyance
Erosion control blanket
Seed mix (ref. plant list)
Topsoil, 4 in min. depth
Figure 7-9. Sample grass-lined swale (Horner, 1988).
120
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Grassed swales provide little removal of dissolved
pollutants, such as nutrients. Based on many studies of
grassed swale effectiveness, removal rates are high for
metals and particulates (Pitt, 1989).
Design Considerations. Pollutant removal in grassed
swales can be increased by reducing runoff velocity—
reducing the slope, increasing the vegetation density,
and installing check dams to promote ponding. Also, the
underlying soils should have a high permeability to help
promote infiltration.
Maintenance Requirements. Grassed swale maintenance
is aimed at preserving dense vegetation and preventing
erqsion of underlying soils. This maintenance includes
regular mowing, weed removal, and watering during
drought periods and after initial seeding. In conjunction
with mowing, the cut material should be removed.
Limitations on Use. Grassed swales might be difficult to
retrofit in already developed areas. They can replace
curb and gutter drainage systems, but work best in
low-slope areas with soil that is not susceptible to
erosion.
Filter Strips. Filter strips, shown in Figure 7-10, are
similar to grassed swales. Runoff entering these
systems, however, generally is sheet flow, is evenly
distributed across the filter strip, and flows
perpendicular to the filter strip. Because these systems
can accept only overland sheet flow, level spreading
devices are used so that water is not ponded.
Pollutant Removal. Pollutant removal in filter strips
depends on the filter strip's length, size, slope, and soil
permeability; the size of the watershed; and the runoff
velocity (Horner, 1988). Filter strips are most effective
at removing pollutants such as sediment, organic
material, and some trace metals, and less effective at
removing dissolved pollutants such as nutrients.
Design Considerations. The major design aspects of
filter strips that can be effectively changed are the
length, width, slope, and vegetative cover of the strip.
Greater pollutant removal results from filter strips that
are long and flat. A level spreading device must also be
incorporated in the design of a filter strip to ensure that
concentrated flow does not enter and create a channel.
If concentrated flows enter a filter strip, they can cause
erosion of the vegetation and soil and reduce the
structure's pollutant removal efficiencies. In addition to
these considerations, filter strips should be constructed
in areas with porous soil to promote infiltration.
Grassed
area
(plants and trees)
Stone trench
level spreader
Figure 7-10. Schematic design of a filter strip.
121
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Maintenance Requirements. Filter strips must be
mowed and weeded regularly—the same maintenance
practices as grassed swales. In addition, the strip must
be watered after initial seeding. In some cases,
however, large filter strips can be "left on their own" so
that large vegetation can grow and create a natural filter
strip. This option reduces the level of maintenance
required and can enhance the pollution removal of the
strip.
Limitations on Use. The major limitation on the use of
filter strips is the slope of the land; these strips operate
best when placed on flat surfaces that have permeable
soils. Also, filter strips treating large watersheds can
have large land requirements that preclude their
location in urban areas.
Filtration Practices
Filtration practices provide runoff treatment through
settling and filtering using a specially placed layer of
sand or other filtration medium. Flow enters the
structure, ponds for a period of time, and filters through
the media to an underdrain that discharges to a surface
water. These practices attempt to simulate the pollutant
removal of Infiltration practices using less land area.
Two different types of filtration practices currently in use
are filtration basins and sand filters.
Filtration Basins. Storm water runoff diverted to a
filtration basin can be detained, allowed to percolate
through filter media, and collected in perforated pipes
as shown in Figure 7-11. These perforated pipes then
transport the filtered runoff to the receiving water.
These systems have been used extensively in Austin,
Texas, showing good pollutant removal efficiencies
and low failure rates (City of Austin, TX, 1990).
Communities in other regions might experience some
initial problems in importing the technology (U.S. EPA,
1991 a). One major question regarding filtration basins
Is the effect of cold temperature and freezing
conditions on the operation of these systems.
Pollutant Removal. Pollutant removal in filtration basins
occurs because of settling during the initial ponding time
and filtering through the soil media. Removal
efficiencies in filtration basins depend on several
factors, including the storage volume, detention time,
and filter media used. In general, longer detention times
increase the system's pollutant removal efficiency.
Increasing the detention time usually requires
increasing the overall size of the filtration basin.
Initial settling of suspended solids occurs in filtration
basins during the initial ponding of the runoff. Increasing
detention time therefore promotes settling and
increases the pollutant removal efficiency. Reducing the
size of the perforated pipe, increasing the depth of filter
medium, or decreasing the percolation rate of the filter
medium can be used to increase the detention time.
Changes in the filter medium also affect the pollutant
removal efficiency of filtration basins. To date, filtration
basins have primarily used sand as the filtering medium.
Recent studies, however, have investigated the use of
a combination of sand and peat, taking advantage of
the adsorptive properties of peat to increase pollutant
removal efficiencies (Galli, 1990). These sand-peat
systems, however, are generally untested and their
pollutant removal efficiencies are only theoretical.
Design Considerations. In Austin, Texas, sand filtration
basins are typically designed to provide a detention time
of 4 to 6 hours and have been used to treat runoff from
drainage areas from three to 80 acres (City of Austin,
TX, 1990). An experimental storm water sand-peat
filtration basin to be constructed in Montgomery County,
Maryland, is being designed to store the first one-half
inch of rainfall from the impervious land in the
watershed. In the Maryland area, this sizing criterion
results in the treatment of 50 to 60 percent of the annual
storm runoff volume (Galli, 1990). Runoff from larger
storms will exceed the capacity of these filtration
systems and will be diverted away from the filtration
basin or discharged through an emergency spillway. To
improve the longevity of sand and sand-peat filtration
basins, runoff entering the systems is typically
pretreated to remove suspended solids. Such
pretreatment techniques as the use of a wet pool or
n
Cleanout
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n
i— Geotextile fabric
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Figure 7-11. Conceptual design of a filtration basin (City of Austin, TX, 1990).
122
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water quality inlets can be used in conjunction with
filtration basins.
Maintenance Requirements. Storm water runoff filtration
basins require extensive maintenance to remove
accumulated sediments and prevent clogging of the
filtering medium. Maintenance requirements include
inspecting the basin after every major storm event for
the first few months after construction and annually
thereafter; removing litter and debris; and revegetating
eroded areas. In addition, the accumulated sediment
should be removed periodically and the filter medium,
when clogged with sediment deposits, should be
removed and replaced (U.S. EPA, 1991b).
Limitations on 'Use. Filtration basins can often be
difficult to locate in highly urbanized areas because of
their large land requirements. In addition, high ground-
water levels can restrict their use. Finally, they have not
been widely used throughout the country and might not
be considered a proven technology.
Sand Filters. Sand filters are similar to the filtration
basins outlined above but can be built underground to
reduce the amount of land required. These systems
consist of a catch basin for settling of heavy solids and
a filtration chamber (see Figure 7-12). Runoff enters
the catch basin and collects to the basin capacity,
overflows into a sand-filled chamber that provides
filtration, and is discharged through an outlet pipe in
the bottom of the filtration chamber. Other types of
systems can be designed in conjunction with wet
ponds or other practices, using natural or imported soil
banks or bottoms, to increase their pollutant removal
capability. The use of sand filters for storm water runoff
treatment has been demonstrated in Maryland
(Shaver, 1991).
Pollutant Removal. Sand filters use the same pollution
removal mechanisms as filtration basins and provide
similar pollutant removal. Initial removal of heavy solids
occurs through settling in the catch basin and further
treatment is provided by filtration through the sand-filled
Plan View
Flow
Drain
Outfall pipe
Section A-A'
Grated cover Solid cover
Row
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Figure 7-12. Schematic design of sand filter (Shaver, 1991).
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chamber. Sand filters are particularly effective at
removing suspended solids and pollutants that attach to
suspended solids, such as metals. Moderate removal of
bacteria can be expected, but these systems cannot
provide removal of soluble pollutants such as nitrogen
and phosphorus.
Design Considerations. Because this BMP has not been
widely used, there are few generally accepted design
criteria for sand filters. The catch basin section must be
designed to provide some sediment removal and to
ensure that flow enters the filtration chamber as sheet
flow to prevent scouring of the sand. The maximum
drainage area that can be treated by a sand filter has
been reported as about 5 acres (Shaver, 1991). Sand
filters generally are used to treat impervious areas, such
as parking lots, so that smaller sediment particles
typical of pervious areas will not clog the sand filter.
Maintenance Requirements. Sand filters require minimal
maintenance, consisting of periodically removing
accumulated sediment and the top layer of sand from
the filtration chamber and removing accumulated
sediment and floatables from the catch basin. Regular
inspections of the filter system can indicate when this
maintenance is required.
Limitations on Use. Because of their small size, sand
filters are designed to be used for pretreatment in large
watersheds or full treatment in small watersheds. They
cannot provide sufficient treatment for large watersheds
(Shaver, 1991).
Water Quality Inlets
Water quality inlets, also known as oil and grit separators,
are similar to septic tanks used for removing floatable
wastes in onsite wastewater disposal systems. These
inlets provide removal of floatable wastes and
suspended solids through the use of a series of settling
chambers and separation baffles as shown in Figure
7-13. These systems have been designed and used for
many years, but storm water pollutant removal
efficiencies are generally unknown.
Given the limited pollutant removal expected from water
quality inlets, they are usually used in conjunction with
other BMPs. Fairly effective at removing coarse
sediments and floating wastes, water quality inlets can
be used to pretreat runoff before it is discharged to
infiltration systems or detention facilities. In this way,
some of the routine maintenance other BMPs require
(e.g., sediment removal and unclogging of outlet
structures) can be reduced. Water quality inlets also can
serve to capture petroleum spills that could enter other
treatment structures or surface waters.
Pollutant Removal. The primary pollutant removal
mechanisms of water quality inlets are separation and
settling. The use of three chambers in these inlets
serves to increase the detention time of the runoff in the
tank, allowing settling to occur. In this way, suspended
solids, and the attached pollutants, are removed from
the runoff. In addition, the use of baffles and inverted
elbows helps to remove floating litter and petroleum
products from the storm water. The level of removal of
these pollutants depends on the volume of water
permanently detained in the tank, the velocity of flow
through the tank, and the depth of the baffles and
inverted elbows in the tank. By increasing detention
time and decreasing flow velocity, the level of sediment
and floatables expected to be removed from water
quality inlets can be improved.
Design Considerations. There are few generally
accepted design criteria for water quality inlets. Their
design depends on the size of the watershed being
treated and the detention time required. Since
suggested detention times are usually measured in
terms of minutes rather than days, water quality inlets
generally do not remove pollutants from storm water
runoff as effectively as some of the more intensive
detention facilities discussed in this section. Water
quality inlets have the advantage of being relatively
small so they can be placed throughout a drainage
system rather than just at the downstream end of the
system.
In water quality inlet design, provisions should be made
to reduce the entering flow velocity. Sediment and
petroleum products collect in the water quality inlets. If
entering flow has a sufficiently high velocity, the
accumulated pollutants can be resuspended and
discharged from the inlet. The flow and velocity of the
entering runoff can be hydraulically restricted by limiting
the size of the inlet pipe. Flows greater than the
maximum design flow should be diverted away from the
water quality inlet by a diversion structure in an
upstream manhole.
Maintenance Requirements. Water quality inlets require
periodic maintenance to remove accumulated pollutants;
in general, these inlets should be cleaned about twice
a year. Cleaning can be performed with a vacuum truck
similar to those used to clean catch basins. The waste
removed from water quality inlets, which includes
petroleum products as well as sediments that have
accumulated in the bottom, should be tested to
determine proper disposal requirements, though their
characteristics are similar to those of catch basin
wastes. Periodic inspections between scheduled
maintenance are also required to determine the level of
accumulated pollutants.
Limitations on Use. There are few physical site
limitations on the use of water quality inlets. The inlets
are generally designed as belowground structures and
do not require large amounts of land. Given their small
size, however, large watersheds cannot be drained into
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a water quality inlet. Removal.efficiencies depend on
the detention time in the water quality inlets. Their use
is usually restricted to small watersheds of less than 2
acres. Another restriction on the use of water quality
inlets is dry-weather base flow. If dry-weather base flow
cannot easily be removed from a drainage system, a
larger water quality inlet and more frequent maintenance
are needed to accommodate this flow as well as the
flow resulting from a rainfall event.
Combined Sewer Overflow Control Practices
Some of the urban runoff BMPs discussed above are
applicable to CSO control. Additional control practices
commonly used for CSO control are described in this
section, including a general discussion of each
practice's applicability, its pollutant removal effectiveness,
• 12-in compacted 3/4-in stone
and its maintenance requirements. More detailed
references on CSO control are presented in Appendix
B. Because CSOs contain sanitary sewage and other
waste streams, the primary pollutants of concern in
CSO control are suspended solids, biochemical oxygen
demand, and pathogens. CSOs, however, also contain
nutrients, metals, and other toxic substances.
Source Controls
Many of the source control practices that address urban
runoff pollution are applicable to CSOs because they
address contaminants that can enter any storm water
collection system, whether separate or combined.
Additional source control measures include water
conservation and pretreatment programs.
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Water Conservation Programs, One way of reducing
the amount of sewage in a combined system is to
attempt to control the amount of water used by homes
and businesses that is then converted to wastewater.
Typical programs and practices for control include:
• Plumbing retrofit: Using low-flush toilets, flush dams,
faucet aerators, and other water-saving devices.
• Plumbing code changes: Requiring implementation
of water-saving devices in new construction or as
they are replaced.
• Education programs: Encouraging water conservation
in businesses and homes by providing information on
its benefits.
• Technical assistance: Providing water-use audits or
case studies demonstrating potential savings to
businesses.
• Rate system modifications: Adjusting rate systems to
promote or reward water savings.
While these programs might require minor changes in
personal habits, they can be cost effective compared to
end-of-pipe treatment. There are limits, however, to the
reductions in water use that can be achieved
reasonably.
Pretreatment Programs. These programs are
Implemented at the local level to control industrial and
commercial sources of wastewater discharging to a
municipal sewer system. The goals of a local
pretreatment program are to stop or prevent industrial
and commercial pollutants from passing through a
municipal wastewater treatment plant, thereby violating
state water quality standards; to stop or prevent
disruption of treatment plant operations caused by
industrial and commercial pollutants,- including the
contamination of municipal treatment plant residuals;
and to ensure the safety of municipal sewer system
and treatment plant workers by minimizing their
exposure to potentially dangerous or toxic pollutants.
While pretreatment programs historically have
controlled large industrial wastewater sources,
programs increasingly are focusing on controlling the
discharges from small businesses and households.
Local pretreatment programs typically include the
following activities:
• Development of sewer-use regulations: To establish
requirements on the quality and quantity of
nondomestic wastewater that can be discharged to a
municipal sewer system and to provide the
municipality with legal authority to ensure compliance
with pretreatment requirements.
• Monitoring and surveillance: To sample and analyze
industrial and commercial discharges and to conduct
onsite inspections of industrial and commercial
facilities to determine the compliance with
pretreatment requirements.
• Permitting and enforcement: To issue permits to
individual industrial and commercial wastewater
discharges that establish site-specific pretreatment
requirements and to take all necessary actions to
ensure compliance with those requirements.
• Technical assistance and education programs: To
provide assistance to the regulated industries and
commercial facilities, including encouragement to use
pollution prevention measures to address wastewater
control problems and to educate the general public
on the effects of common household products and
wastes that are discharged to the sewer system.
A pretreatment program implemented in a municipality
with combined sewers can help control industrial and
commercial pollutants discharged from CSOs during
storm events. The level to which a pretreatment
program can control the quality of CSO discharges,
however, is very difficult to determine. Nonetheless, as
part of an overall program to decrease the deleterious
effects of CSOs, a pretreatment program can provide
positive results.
Collection System Controls
Many collection system controls exist for addressing
pollution from CSO discharges. These controls focus on
modifying the sewer system to reduce CSO flow,
volume, and contaminant load.
Sewer Separation. One method for addressing CSO
pollution is to convert the combined collection system
to separate storm water and sanitary sewer systems by
constructing a new separate sanitary sewer. Sewer
laterals from homes and businesses are then
connected into the new system. Inappropriate
connections to the old system from buildings are
plugged. This conversion eliminates the possibility of
sanitary wastes entering the drainage system and
being discharged to a surface water. Sewer separation,
however, can be very expensive and disruptive. A
municipality implementing this practice likely has to
address urban runoff pollution problems. In systems
that consist of both combined and separate drainage
areas, partial separation (i.e., separation of some
combined areas) could be cost-effective.
Infiltration Control. Sources of infiltration include
ground water entering the collection system through
defective pipe joints, cracked or broken pipes, and
manholes as well as footing drains and springs.
Infiltration flow rates tend to be relatively constant, and
result in lower volumes than inflow contributions.
Infiltration problems are usually not isolated, and often
reflect a more general sewer (or drainage) system
deterioration. Extensive rehabilitation is typically required
126
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to remove infiltration effectively. The rehabilitation
effort often must include house laterals, which are
normally a significant source. Except in very large
drainage systems, control of infiltration generally has a
much smaller impact on CSO reduction than control
applied to inflow.
Inflow Control. CSO control can be achieved by
diverting some of the surface runoff inflows from the
combined sewer system, or by retarding the rate at
which these flows are permitted to enter the system.
Inflow of surface runoff can be retarded by using
special gratings, restricted outlet pipes, or hydrobrakes
(or comparable commercial devices) to modify catch
basin inlets to restrict the rate at which surface runoff is
permitted to enter the conveyance system. Inlet flow
restrictions can be designed to produce acceptable
levels of temporary ponding on streets or parking lot
surfaces, allowing runoff to enter the system eventually
at the inflow point, but reducing the peak flow rates that
the combined sewer system experiences. Flow
detention to delay the entry of runoff into the collection
system by storing it temporarily and releasing it at a
controlled rate can also be accomplished by rooftop
storage under appropriate conditions. Elimination of
the direct connection of roof drains to the CSO
collection system and causing this runoff to reach the
system inlets by overland flow patterns (preferably via
unpaved or vegetated areas) is another method of
retarding inflows.
When site conditions permit, some surface runoff flows
can be prevented from entering the combined system,
by diverting them via overland flow to pervious areas or
to separate storm drains. When these outlets are not
available, excess surface runoff flows can be diverted
to more favorable locations in the combined system
(called flow-slipping).
Regulator and System Maintenance. Malfunctioning
regulators are a common problem for combined sewer
systems and can result in dry-weather overflows to
receiving waters or in system backups and flooding.
Static regulators often malfunction because of plugging
or interference by debris in the sewer system.
Mechanical regulators tend to require frequent
maintenance. Municipalities should, therefore, develop
an inspection and maintenance program designed to
keep these regulators operating as designed. The
expected reduction in CSO flows and loads resulting
from this maintenance is site specific and depends on
the existing conditions in the system.
In-System Modifications. These practices are
designed to reduce CSO discharges by modifying the
system to store more flow and allow it to be carried to
the treatment plant. Possible modifications include
adjusting regulator control features, such as weir
elevation; installing new regulators; or installing new
relief conduits. The effectiveness and applicability of
these practices is site specific and depends on the
existing capacity of the system and the treatment plant.
These practices can be cost effective in locations
where excess capacity exists.
Sewer Flushing. Sewer flushing is an additional
practice to address CSO pollution problems. In this
practice, water is used to flush deposited solids from
the combined system to the treatment plant during dry
weather. This practice is typically used in flat areas of
the collection system where solids are most likely to
settle out. The effectiveness of this practice is site
specific and depends on the flush volume; flush
discharge rate; wastewater flow; and sewer length,
slope, and diameter. Though not currently a widely
used practice, sewer flushing has been tested in
selected areas (WPCF, 1989).
Storage
CSO discharges occur when the flow in a combined
system exceeds the capacity of the sewer system or the
treatment plant. Storing all or a portion of the CSO
discharges for treatment during dry weather can
effectively reduce these overflows. Storage techniques
include in-line and off-line storage.
In-Line Storage. In-line storage uses existing capacity
in major combined sewer trunk lines or interceptors to
store combined flows. During storms, regulators are
used to cause flow to back up in the system allowing it
to be stored in the system. While not all flow can be
stored in the sewer system, this practice can reduce
overflow volumes during large storms and eliminate
overflow volumes during small storms. After a storm,
stored flow proceeds to the treatment plant for
treatment. The overall pollutant removal in this practice
depends on the level of storage space available in the
existing system. Care must be taken to ensure that
flows do not back up onto streets or into homes.
Off-Line Storage. Off-line storage consists of
constructed near-surface or deep tunnel detention
facilities. Near-surface facilities usually consist of
concrete tanks or, in some cases, large conduits which
also convey flow to a treatment facility. Tunnels can
provide large storage volumes with relatively minimal
disturbance to the ground surface, which can be very
beneficial in congested urban areas. Overflows are
directed to the storage facility, held during the storm,
and pumped to the POTW after the storm, thus
reducing the overflow quantity and frequency. The
overall pollutant removal in this practice depends on
the design capacity of the storage facility and the
percentage of overflows that can be stored.
Flow Balance Method. The in-receiving water flow
balance method involves using floating pontoons and
127
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flexible curtains to create an in-receiving water storage
facility. CSO flows fill the facility by displacing the
receiving water that normally occupies the storage
facility. The CSO flows are then pumped to the
collection system following a storm. The technology
has been used for CSO control in Brooklyn, New York.
This alternative involves permanently installing the
floating pontoons in the receiving water near the CSO
outlets. The feasibility of this technology, therefore,
depends in part on whether the storage facility would
have a significant impact on the aesthetic value of the
surrounding area, and whether the structure would be
a hindrance to navigation. Other site-specific concerns
include the availability of volume due to tidal variations
in coastal waters and the need for protection from
damage due to high winds or wave action.
Physical Treatment
Most of the urban runoff BMPs previously discussed
employ physical processes to reduce pollution. Physical
treatment practices can also be used to reduce pollutant
discharges from CSOs. The practices discussed in this
section include bar racks and screens and swirl
concentrators/vortex solids separators.
Bar Racks and Screens. These practices use
screening technologies to reduce the flow of solids in
combined systems. They are typically used as a
preliminary treatment step to remove floatables
upstream of other processes. Different screens have
different size openings to provide various levels of
solids removal. Bar racks have the largest openings
(typically 1 inch or more) and microstrainers have the
smallest openings (typically as small as 15 microns).
All these practices require periodic and regular
cleaning to prevent the accumulation of solids.
Typically only the smaller screens provide significant
pollutant removal. Screens are most effective at
removing floatables and, depending on screen size,
can remove suspended solids and can provide some
BOD removal.
Swirl Concentrators/Vortex Solids Separators. These
technologies are designed to provide flow regulation
and remove solids from combined flow by forcing flow
into a vortex path, so that solids and nonsolids can be
separated. The resulting underflow containing separated
solids can then be conveyed to a treatment facility.
One advantage of these structures is that they have no
moving parts and thus require less maintenance
than other structures. The effectiveness of swirl
concentrators and vortex solids separators depends on
the settling characteristics of the CSO solids, the
amount of turbulence created in the structure, and the
flow rate. Data have shown that these practices can
provide up to 60-percent removal of solids and BOD,
with the greatest removal occurring during the first
flush washoff (WPCF, 1989). They are, however, most
effective in removing larger solids; their performance is
highly dependent on the influent solids particle size
distribution and specific gravity.
Dissolved Air Floatation. Dissolved air floatation
(DAF) removes solids from wastewater by introducing
fine air bubbles which attach to solid particles
suspended in the liquid, causing the solids to float to
the surface where they can be skimmed off. While this
technology has been tested in CSO applications, it has
not been widely applied. Because of its relatively high
overflow rate and short detention time, DAF does not
require as large a facility as conventional
sedimentation. Oil and grease are also more readily
removed by dissolved air floatation. The high operating
costs for DAF are due to large energy demand; skilled
operators are required for its operation.
Fine Screens and Microstrainers. These devices
remove solids through capture on screen media. The
most common fine-screening devices include rotary
drum and rotary disk devices. In the rotary drum
screen, media is mounted on a rotating drum. Flow
enters the end of the drum, and passes out through the
filter media. Drum rotational speed is usually
adjustable. Solids retained on the inside of the drum
are backwashed to a collection trough. Filter media
aperture size typically ranges from 15 to 600 microns.
The rotary disk screen has the screening media
mounted on a circular frame placed perpendicular to
the flow. Flow passes through the bottom half of the
rotating disk, which is submerged. Solids retained on
the disk are directed to a discharge launder using
spray water.
One form of static screens features wedge-shaped steel
bars, with the flat part of the wedge facing the flow.
These wedge-wire screens typically have openings
ranging from 0.01 to 0.05 in. These screens require
daily maintenance to prevent clogging (Metcalf & Eddy,
Inc., 1991). Screens are subject to blinding from grease
and first-flush solids loads; a high-pressure backwash,
as well as the collection and conveyance of backwash
solids, are typically required. Effective cleaning of
screens after storm events using high pressure steam
or cleaning agents is typically required to maintain
performance. Removal efficiencies can be increased by
decreasing media aperture size, but smaller apertures
are more likely to blind. Coarse screening and
disinfection facilities are often provided in conjunction
with microstrainers.
Filtration. Dual-media high-rate filtration has been
piloted for treatment of CSO flows using a two-layer
bed, consisting of coarse anthracite particles on top of
less coarse sand. After backwash, the less dense
anthracite remains on top of the sand. Filtration rates
of 8 gal/f^/min or more result in substantially smaller
area requirements compared with sedimentation.
128
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Demonstration test systems include pretreatment by
microstrainers. The use of chemical coagulants
improves performance considerably. A disadvantage to
filtration is the filters' tendency to clog during use in
treating wastewater, thus limiting hydraulic capacity
and effectiveness of solids removal. Filtration is more
appropriately applied after sedimentation or fine
screening to provide pretreatment. While operation can
be automated, filtration tends to be O&M intensive.
Chemical Precipitation
Chemical precipitation facilities store and use polymer,
alum, or ferric chloride to cause solids to precipitate.
Chemical precipitation can increase the pollution
removal that generally occurs from other settling
practices, thereby allowing for the design of smaller
sedimentation tanks. Chemical precipitation generates
more sludge than other settling techniques. Pollutant
removal depends on the types of chemicals used and
the characteristics of the combined flow. Removal rates
for these practices are up to 70 percent for BOD and
85 percent for suspended solids. Because CSO
treatment facilities are intermittently operated, however,
sludge buildup and handling can become a major
problem.
Biological Treatment
While biological treatment processes have the potential
to provide a high quality effluent, disadvantages of
biological treatment of CSOs include:
• The biomass used to break down the organic material
and assimilate nutrients in the combined sewage
must be kept alive during dry weather, which can be
difficult except at an existing treatment plant;
biological processes are subject to upset when
exposed to intermittent and highly variable loading
conditions.
• The land requirements for these types of processes
can preclude their use in urban areas.
• Operation and maintenance can be costly and the
process requires highly skilled operators.
Some biological treatment technologies are utilized in
CSO control as elements of a wastewater treatment
plant. Pump-back flows from CSO storage facilities
commonly receive secondary treatment at the treatment
plant, once wet-weather flows have subsided. In a
treatment plant that has maximized the wet-weather
flows it accepts, flows are sometimes split, with only a
portion of the primary treated flows receiving secondary
treatment; to avoid process upset. The split flows are
blended and disinfected for discharge.
Disinfection
Because pathogens are the primary pollutant of concern
in CSO control, practices focusing on disinfection are
commonly used.
Chlorination. Combined flows can be treated with
dissolved or gaseous chlorine to reduce the level of
pathogens in the flow. Chlorination is typically used in
conjunction with upstream solids removal. Chlorination,
however, is not effective at addressing aesthetic or
other water quality impacts of CSOs. Dissolved
chlorine (hypochlorite) is currently more commonly
used than gaseous chlorine because the equipment is
more reliable and storage of the chemicals is safer.
Dechlorination might be necessary to minimize the
adverse effects of chlorine on aquatic life.
Effectiveness of disinfection depends on the amount of
chlorine used and the contact time between the
chlorine and the wastewater. With sufficient dosage
and mixing, close to 100-percent destruction of
pathogens is possible. These facilities require regular
inspection and maintenance.
UV Radiation. Introduction of ultraviolet radiation to
combined wastewater is designed to provide
disinfection without the addition of harmful chemicals.
This practice uses an ultraviolet lamp submerged in a
baffled channel located downstream of an effective
solids removal process. The effectiveness of this
practice depends on the lamp intensity, the contact
time between the lamp and the wastewater, the
distance between the wastewater and the lamp, and
the level of solids in the wastewater. This system
provides disinfection only and does not contribute to
removing other pollutants. The high amount of solids in
CSO flows limits the performance of UV radiation
unless the solids can first be reduced.
An overview of urban runoff and CSO BMPs is given to
help develop a list of BMPs to be screened. As noted
earlier, many references also can be used (see
Appendix B). After the BMPs have been screened, BMP
selection is the next step of the planning approach.
129
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Case Study:
City of Austin, Texas,
Local Watersheds Ordinances
Austin, a highly urbanized city bisected by the Colorado River, contains a number of high quality lakes,
aquifers, and streams. The major water resources in the area include three lakes—Lake Travis, Lake
Austin, and Town Lake—which form a major drinking-water reservoir acting as the main water supply
for the city; Edwards Aquifer and Barton Springs are the area's other major water resources. These
water resources are potentially threatened by urban runoff pollution from urbanized areas; Town Lake
already is affected significantly. To reduce and prevent urban runoff pollution problems in these
resources, Austin has developed and passed three major watershed ordinances:
• The Comprehensive Watersheds Ordinance, 1986
• The Urban Watersheds Ordinance, 1991
• The Barton Springs Ordinance, 1992
The primary goal of these ordinances is to protect the water resources of the Austin area from
degradation from nonpoint source pollution. Other goals include preventing the loss of recharge to the
Edwards Aquifer, preventing adverse impacts from wastewater discharges, and protecting the natural
and traditional character of the water resources in the Austin area. In addition, the city has implemented
other ordinances that control NPS pollution.
Water pollution problems in the Austin area have been extensively studied since the mid-1970s. In 1981,
the city participated in NURP and began implementing and monitoring the effectiveness of urban runoff
structural controls. The city has been a leader in developing and implementing NPS regulatory controls. The
city's first NPS control ordinance, the Lake Austin Watershed Ordinance in 1978, was followed by other
watershed ordinances in 1981 and 1984 designed to protect additional sensitive watersheds and upgrade
the level of protection. The experience and data gathered as a result of these ordinances led the city to
propose and adopt a more complete set of protections for water resources as described in this summary.
The Comprehensive Watersheds Ordinance
The Comprehensive Watersheds Ordinance (CWO) is directed at preventing urban runoff pollution by
placing requirements on proposed new developments within a 700-square-mile area of the city and its
extraterritorial jurisdiction. It was developed in 1986 by a task force, appointed by the city council, with
representatives from environmental groups, citizens, developers, and a council-appointed environmental
board. The ordinance includes requirements for limiting impervious cover, using water quality buffer
zones, protecting critical environmental features, limiting the disturbance of natural streams,
implementing erosion control practices, constructing sedimentation and filtration basins, and restricting
onsite wastewater disposal. The ordinance divides the city into four different watershed categories that
each allow for different levels of development intensity: urban, suburban, water supply suburban, and
water supply rural. While urban watersheds were not originally covered by the CWO, they are addressed
in the Urban Watersheds Ordinance which is described later. Requirements for all the applicable
watershed categories are shown in Table 7-3.
The waterways located in each watershed category are classified as minor, intermediate, or major
depending on the total drainage area contributory to the waterway (see Table 7-3). Each waterway
classification has an associated critical water quality (WQ) zone which encompasses the 100-year
floodplain boundary and is located 50 to 100 feet from minor waterways, 100 to 200 feet from
intermediate waterways, and 200 to 400 feet from major waterways. No development is allowed in this
critical WQ zone. Each waterway type also has an associated water quality buffer zone that begins at
the end of the critical WQ zone and extends upland for a defined distance as shown in Table 7-3.
Development in this zone is restricted by limits on the allowed percent imperviousness of the site. Areas
outside the WQ buffer zone are considered upland areas and have less stringent percent imperviousness
130
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Table 7-3. Maximum Development Intensity
Waterways
Watershed Inter-
Category Minor mediate
Suburban
Drainage area: 320 ac 640 ac
Critical WQ zone: 100 ft 200 ft
WQ buffer zone: None 100 ft
Water Supply Suburban — Class 1
Drainage area: 128 ac 320 ac
Critical WQ zone: 100 ft 200 ft
WQ buffer zone: 100 ft 200 ft
Water Supply Suburban — Class II
Drainage area: 128 ac 320 ac
Critical WQ zone: 100 ft 200 ft
WQ buffer zone: 100 ft 200 ft
Water Supply Suburban— Class III
Drainage area: 320 ac 640 ac
Critical WQ zone: 100 ft 200 ft
WQ buffer zone: 100 ft 200 ft
Water Supply Rural
' Drainage area: 64 ac 20 ac
Critical WQ zone: 100 ft . 200 ft
WQ buffer zone: 100 ft 200 ft
a Net site area.
Major
1,280ac
400ft
150ft
640 ac
400ft
300ft
640 ac
400ft
300ft
1,280ac
400ft
300ft
640 ac
400ft
300ft
Except in Lake Austin/Lake Travis, where filtration
0 Only at major intersections.
Development Limits
Water Quality
Buffer Zone
30-percent
impervious cover
18-percent
impervious
cover; no
development
over recharge
zone
30-percent
impervious
cover; no
development
over recharge
zone
30-percent
impervious cover
One unit per 3
acres; no
development
over recharge
zone
is required.
Area Type
Residential:
Duplex:
Multifamily:
Commercial:
Residential:
Multifamily:
Commercial:
Residential:
Multifamily:
Commercial:
Single-family:
Duplex:
Multifamily:
Commercial:
Single-family:
Cluster:
Multifamily:
Commercial:
Planned:
Retail:
Uplands
Zone9 Transfer
% Impervious
Cover •
50 60
55 60
60 70
80 90
% Impervious
Cover
30 40
40 55
40 55
% Impervious
Cover
40 55
60 65
60 70
% Impervious
Cover
45 50
55 60
60 65
65 70
Unlts/ac
0.5 1.0
1.0 2.0
% Impervious
Cover
20 25
20 25
50 50
50-60° 60-70
Acceptable
Cfviiftfiiral
oiruciurai
Pollution
Controls
Sedimentation
Sedimentation
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
Filtration
40% buffer"
40% buffer
40% buffer
40% buffer
Filtration
131
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restrictions. In this zone, the restrictions are tied to the type of development proposed for the site as
shown in Table 7-3. Some development restrictions can be reduced if the developer transfers land
located in the watershed to the city. In this way, development density can be increased by the developer
in exchange for an increase in publicly held lands. For example, a multifamily development in suburban
Class I water supply watershed is restricted to 40-percent impervious unless the developer is able to
use development rights transfers (see Table 7-3). In this case, the development can reach 55-percent
impervious and still meet the requirements of the ordinance.
In addition to the restrictions on site percent imperviousness, developments in these watersheds are
required to incorporate structural control practices. The acceptable control practices are sedimentation
basins, filtration basins, and vegetative buffers as outlined in Table 7-3. Basins must be designed to
capture, isolate, and hold at least the first one-half inch of runoff from contributing drainage areas. Also,
nonstructural requirements serve to prevent pollution. These include limitations on the depth of cuts and
fills, limitations on construction on steep slopes (greater than 15 percent), and limitations on the
disturbance of natural streams including restrictions on the number of stream crossings. Temporary
erosion controls, such as silt fences and rock berms, are required during construction.
In Austin, proposed new development plans are reviewed by a separate environmental review staff,
autonomous from other departments. This allows for a focused review that includes field surveys of
projects in sensitive areas. Once the plans are approved, city inspectors monitor construction for
compliance with the approved plans. Approximately 50 percent of the financing for reviews and
inspections required by this ordinance comes from development permit fees. The fees vary depending
on the development size and are higher in sensitive watersheds because of the increased review
requirements. The rest of the expenses are covered through a drainage utility fund which consists of
monthly service charges to the residents in the utility service area.
Since these requirements apply to new developments, the CWO is designed to prevent or reduce future
increases in pollutant load to the target water bodies. The ordinance can be applied to a variety of
watershed characteristics and water resource types.
Given the short time this ordinance has existed and its focus on prevention, assessing its effectiveness
is difficult. These control measures, however, have been shown to reduce urban runoff pollution on a
nationwide and a local level. The city's analysis of its nonpoint source monitoring program, completed
in 1990, showed that pollutant loads increase with increased impervious cover. Figure 7-14, based on
that 1990 report, compares total suspended solid loads from land with various levels of development as
measured by percent impervious cover. This type of data was used to define the impervious land
limitations in the ordinance.
Urban Watersheds Ordinance
In 1991, the city council approved task force recommendatiohs to include urban area watersheds among
those covered by development ordinances. This ordinance, created in response to increased pollution
in Town Lake due to urban runoff discharges, focuses on the urban watersheds not previously covered
by the CWO. It requires the implementation of structural controls in new developments undergoing site
plan review. All new residential, multifamily, commercial, industrial, and civic development in the urban
watersheds are required to construct water quality basins (either sedimentation or filtration basins) or
provide a cash payment to the city for use in an Urban Watersheds Structural Control Fund. Structural
controls must be used to capture the first one-half inch of runoff from all contributing areas. The
Watersheds Structural Control Fund is used to retrofit and maintain structural controls where required
in the urban watersheds. In addition to this requirement, new developments in the urban watersheds are
required to provide for removal of floating materials from storm water runoff through the use of oil/water
separators or other practices. Redevelopment projects in the urban watersheds are also included in this
ordinance, where structural controls and the removal of floatable materials are required. For
redevelopment projects, the city has, developed a Cost Recovery Program Fund to provide 75 percent
of the cost of structural controls. These funds will be allocated through the drainage utility fund.
132
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n TSS Loading, nonrecnarge zone
O TSS Loading, recharge zone
II I
1,200
1,000
800
-„ 600
400
200
0 10 20 30 40 50 60 70 80 90 100
Percent Impervious Cover
Figure 7-14. Total suspended solids loading vs. percent impervious cover.
In urban watersheds, the critical WQ zone is the boundary of the 100-year floodplain and is generally
located 50 to 400 feet from the waterway. As with the Comprehensive Watersheds Ordinance, no
development is allowed in the critical WQ zone.
Since this ordinance was passed only recently, there are no data concerning its effectiveness. Like the
CWO, however, it focuses on using proven structural and nonstructural control measures that the city
believes will effectively prevent urban runoff pollution.
Other Nonpoint Source Control Programs
In addition to the CWO and the Urban Watersheds Ordinance, Austin has developed other ordinances
designed to reduce nonpoint source pollution from new developments and redevelopments. One of
these, the Barton Springs Zone Ordinance, provides special protection to watersheds contributing to
Barton Springs, a widely visited and used natural spring bathing area in Austin. This ordinance, created
to be a nondegradation ordinance with specific performance requirements, includes definitions of
waterways and development limits similar to those specified in the CWO. Only one- or two-family
residential development with a density of 1 unit per 3 acres is allowed in the Barton Springs watershed
transition zone, which extends up to 300 feet from the water body. In addition, new developments in the
Barton Springs watershed must comply with the following requirements (see Table 7-4): reduce pollutant
concentrations compared with the undeveloped conditions and discharge no greater than a specific
maximum pollutant concentration after development. The city measures these requirements quarterly on
each development through a developer-funded monitoring program.
Additional NFS control programs in Austin include:
• Land Development Code: Enforces landscaping regulations and protects trees and natural areas in
"the city.
• Underground Storage Tank Program: Develops guidelines for underground storage of hazardous
materials, permitting and inspection of these underground storage tanks, and investigation of problems
and response to emergency situations.
• Water Quality Retrofit Program: Involves engineering and building, with private sector participants,
permanent controls for already developed areas and are producing storm water runoff pollution
problems for the city's key receiving waters.
133
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Table 7-4. Barton Creek Development Requirements
Pollutant
Percent Reduction
from Background
Maximum Discharge
Concentration, mg/L
Total suspended solids
Total phosphorus
Total nitrogen
Total organic carbon
60%
15%
15%
50%
144
0.11
0.95
14
Water Quality Monitoring Program: Monitors and characterizes pollutants from various land uses and
structural controls, monitors surface and ground-water quality, and develops water quality models and
data bases; also conducts specific studies on known nonpoint source problems.
Household Chemical Collection Program: Provides for safe disposal of hazardous materials and other
wastes generated from household use; conducted for the past 6 years, this program is currently
located at a permanent site where collection events occur each year.
Storm Sewer Discharge Permit Program: Involves permitting and regular inspection of industrial and
commercial discharges to storm sewers and water courses.
Emergency and Pollution Incident Response Program: Involves responding to emergency spills,
general water pollution incidents, and citizen complaints related to water quality.
Street Cleaning and Litter Collection Program: Provides regular street cleaning—nightly in the central
business district, monthly on other major roads, and bimonthly in residential neighborhoods.
Integrated Pest Management Program: Encourages application of the most environmentally safe
pesticide techniques practicable for pest management in municipal operations.
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
City of Austin, TX. 1990. Removal efficiencies of
stormwater control structures. Environmental
Resource Management Division, Environmental and
Conservation Services Department.
Galll, J. 1990. Peat-sand filters: a proposed stormwater
management practice for urbanized areas. Department
of Environmental Programs, Metropolitan Washington
Council of Governments. Washington, DC.
Horner, R. 1988. Biofiltration systems for urban runoff
water quality control. Washington State Department
of Ecology. Seattle, WA.
Undsey, G., L Roberts, and W. Page. 1991. Stormwater
management infiltration practices in Maryland: a
second survey. Maryland Department of the
Environment, Sediment and Stormwater Administration.
Baltimore, MD.
Livingston, E., E. McCarron, J. Cox, and P. Sanzone.
1988. The Florida development manual: a guide to
sound land and water management. Florida
Department of Environmental Regulation. Stormwater/
Nonpoint Source Management Section.
MD WRA. 1986. Maryland Water Resources Authority.
Minimum water quality and planning guidelines for
infiltration practices. Maryland Department of Natural
Resources.
Metcalf & Eddy, Inc. 1991. Wastewater engineering:
treatment, disposal, reuse. New York, NY: McGraw-
Hill, Inc.
MPCA. 1989. Minnesota Pollution Control Agency.
Protecting water quality in urban areas. St. Paul, MN.
Moffa, P. 1990. Control and treatment of combined
sewer overflows. New York, NY: Van Nostrand
Reinhold.
Pitt, R. 1989. Source Loading and Management Model:
an urban nonpoint source quality model—volume I:
model development and summary. University of
Alabama, Birmingham.
134
-------
RIDEM. 1989. Rhode Island Department of
Environmental Management. Artificial wetlands for
stormwater treatment: processes and designs. Rhode
Island Nonpoint Source Management Program.
Roesner, L.A., B. Urbonas, and M.B. Sonnen. 1988.
Design of urban runoff quality controls: proceedings
of an engineering foundation conference on current
practice and design criteria for urban quality control.
Potosi, MO. July. Published by the American Society
of Civil Engineers, New York, NY.
Schueler, T. 1987. Controlling urban runoff: a practical
manual for planning and designing urban BMPs.
Metropolitan Washington Council of Governments.
Shaver, E.H. 1986. Infiltration as a stormwater
management component. Maryland Department of
the Environment, Sediment and Stormwater
Administration. Delaware Department of Natural
Resources. Dover, DE.
Shaver, E.H. 1991. Sand filter design for water quality
treatment. Delaware Department of Natural Resources.
Dover, DE.
ULI. 1981. Urban Land Institute. Water resource
protection technology: a handbook of measures to
protect water resources in land development.
Washington, DC.
U.S. EPA. 1973. U.S. Environmental Protection Agency.
Water pollution and associated effects from street
salting. EPA/R2-73/257 (NTIS PB-222795). U.S. EPA
National Environmental Research Center.
U.S. EPA. 1974a. U.S. Environmental Protection
Agency. Manual for deicing chemicals: storage and
handling. EPA/670/2-74/033 (NTIS PB-236152).
U.S. EPA. 1974b. U.S. Environmental Protection
Agency. Manual for deicing chemicals: application
practices. EPA/670/2-74/045 (NTIS PB-239694).
U.S. EPA. 1974c. U.S. Environmental Protection
Agency. Urban storm water management and
technology: an assessment. EPA/670/2-74/040
(NTIS PB-240687).
U.S. EPA. 1977. U.S. Environmental Protection Agency.
Urban storm water management and technology:
update and users' guide. EPA/600/8-77/014 (NTIS
PB-275654). Washington, DC.
U.S. EPA. 1979. U.S. Environmental Protection Agency.
Demonstration of nonpoint pollution abatement
through improved street cleaning practices.
EPA/600/2-79/161 (NTIS PB80-108988). U.S. EPA
Office of Research and Development.
U.S. EPA. 1983. U.S. Environmental Protection Agency.
Results of the nationwide urban runoff program: vol.
1-final report. (NTIS PB84-185552.) Water Planning
Division. Washington, DC.
U.S. EPA. 1987. U.S. Environmental Protection Agency.
Guide to nonpoint source control. Office of Water.
Washington, DC.
U.S. EPA. 1991 a. U.S. Environmental Protection
Agency. A current assessment of urban best
management practices: techniques for reducing
nonpoint source pollution in the coastal zone. U.S.
EPA Office of Wetlands, Oceans, and Watersheds.
U.S. EPA. 1991b. U.S. Environmental Protection
Agency. Postconstruction stormwater runoff
treatment. Washington, DC.
U.S. EPA 19923. U.S. Environmental Protection
Agency. The use of wetlands for controlling
stormwater pollution. Region V. Chicago, IL.
Distributed by the Terrene Institute. Washington, DC.
U.S. EPA. 1992b. U.S. Environmental Protection
Agency. Casco Bay storm water management
project: Concord Gully, Frost Gully and Kelsey Brook
watersheds. U.S. EPA Region I. Boston, MA. January.
U.S. EPA. 1992c. U.S. Environmental Protection
Agency. Decision-maker's storm water handbook: a
primer. U.S. EPA Region V. Chicago, IL.
U.S. EPA. 1993a. U.S. Environmental Protection
Agency. Investigation of inappropriate pollutant entries
into storm drainage systems. Storm and Combined
Sewer Control Program.
U.S. EPA. 1993b. U.S. Environmental Protection
Agency. Guidance specifying management measures
for source of nonpoint pollution in coastal waters.
EPA/840/B-92/002. U.S. EPA Office of Water.
WA DOE. 1991. Washington State Department of
Ecology. Storm water management manual for the
Puget Sound Basin.
Woodward-Clyde Consultants. 1989. Santa Clara Valley
nonpoint source study. Santa Clara Valley Water District.
Woodward-Clyde Consultants. 1990. Urban targeting
and BMP selection: an information and guidance
manual for state NPS program staff engineers and
managers. Final report.
WPCF. 1989. Water Pollution Control Federation.
Combined sewer overflow pollution abatement:
manual of practice FD-17.
135
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Chapter 8
Select Best Management Practices
Urban runoff problems, because of their diverse nature,
need to be addressed through a combination of source
control, regulatory, and structural BMPs. The selected
combination needs to reflect the program goals
(Chapter 3) and the priorities set during the assessment
and ranking of existing problems (Chapter 6). The
planning approach in this handbook recommends a
two-step process for BMP selection. This chapter
covers the second part of the BMP selection process,
which uses the screened list of potentially applicable
BMPs to develop and select the BMPs to be
implemented.
To select BMPs, the alternatives typically are developed
and compared to ensure that all options are considered
and that the best possible plan is selected based on a
predetermined set of selection criteria. While a specific
problem caused by a specific source, might not require
development of alternative BMP plans, for most
programs which tend to deal with multiple sources and
impacts, it is wise to investigate alternatives before
selecting a final set of BMPs. This chapter first
addresses development of alternative plans and then
the selection of recommended BMPs. At the end of this
chapter, two separate case studies on methods of BMP
selection are presented.
Alternatives Development
Alternatives are developed using the BMPs still under
consideration after the screening process (Chapter 7).
The alternatives can include various combinations of
source control, regulatory, and structural BMPs. Source
control and regulatory BMPs are often implemented
across entire regions or jurisdictions. Structural BMPs
can be directed at specific pollutant sources or
implemented across geographic areas, including both
structural BMPs for new development in currently
undeveloped areas or for retrofit in already developed
areas. To address fully the urban runoff pollution
problems in an area, BMPs from all these categories
are often required.
Three commonly used methods for developing
alternatives are discussed in this section. The first starts
with known urban runoff problems and known pollutant
reductions desired. The second develops a range of
possible control levels for evaluation. The third involves
applying specific BMPs throughout a project area. Any
one or a combination of these methods can be used to
develop an urban runoff pollution prevention and control
plan.
In the first method, before developing the alternative
plans, the problems to be addressed and desired level
of control are decided. This information could be
obtained from the problem assessment and ranking
step described in Chapter 6. Various types or
combinations of practices are then developed to meet
the desired control level to address the known
problems. For example, if a program goal is to reduce
fecal coliform bacteria levels to below the criterion for
safe consumption so that shellfishing beds can be
opened, the level of control needed must reduce the
bacteria counts to a known level. Information on the
expected bacteria loadings from various sources is
needed. Combinations of BMPs can then be developed
to achieve the needed control level by focusing on
BMPs that control the various sources. Criteria for
developing alternative BMPs to meet the control level
can include cost, pollutant removal efficiency, site
characteristics, public acceptance, and others.
This alternative development method might lead to an
emphasis on structural controls because these BMPs
focus on addressing pollution problems from known
sources, such as septic tanks, illicit cross-connections
in storm water drains, and others. It has the advantage,
however, of ensuring that known priority problems are
addressed by each alternative. While this method can
be used to develop alternatives for meeting either water
quality or technology-based goals, it is especially
applicable for meeting specific water resource or
pollutant removal goals.
An example of this BMP selection method is shown in
Table 8-1. In this example, multiple pollution problems,
such as agricultural runoff, urban runoff, and failed
onsite septic systems, were contributing to closed
shellfish beds. Table 8-1 compares various urban
runoff control practices for cost, level of expected
improvement, public agency support, and other factors
137
-------
Table 8-1. Sample BMP Selection (Metcalf & Eddy, Inc., 1989)
BMP
Technical
Feasi-
Monetary Factors
Water Public Other
Quality and NPS
Improve- Agency Control
billty Capital O&M Funding ment Support Efforts
Demon-
stration
Value Comments
Urban Runoff
Source controls
Infiltration
Storage +
Treatment +
Land Disposal
Sawering +
Alternative disposal +
Nonstructural
Low Mod.
Mod. Low
High High
High High
High
High
High
Low
Does not achieve WQ
goals
Soil and ground water
might preclude its use
Effective pollutant
removal
No bacteria removal
High capital cost
Environmental impacts
High capital cost
High capital cost
Likely public opposition
Regulation and
enforcement
Tax Incentives
Local financing
Beneficiaries
financing
Public education
+ Low - - - - _ Extensive public support
required
- - + + - + No programs in place
— - + - - + Town funding not
available
- - + -,-+ Complete organizational
requirements
+ Mod. Low + + + + + Builds public awareness
and support
+ = Favorable or present
— « Unfavorable or not present
to determine the best mix of practices for
implementation.
Based on this review, a combination of regulatory,
educational, and structural runoff pollution prevention
and control practices was recommended: enacting
stricter local zoning and conservation bylaws oriented
toward runoff pollution prevention, constructing an
infiltration system along a stretch of roadway with
known high pollution levels, conducting a public
education program, and improving ongoing water
resource monitoring efforts.
In the second method, alternatives representing a range
of control levels are developed. For example, three
tevels of control could be formulated based on a range
of pollutant removals (i.e., low, medium, and high). The
low-level control alternative might consist of a minimum
mbc of BMPs designed to address priority problems. The
medium-level control alternative might consist of the
same practices as the low-level control alternative plus
additional BMPs designed to address additional
problems or to address more fully the same priority
problems. The high-level control alternative might
include the practices of the medium-level control
alternative as well as additional practices. Each
alternative plan therefore contains a subset of the BMPs
included in the next higher level control alternative,
allowing for a cost-effectiveness comparison among
various control levels.
An example of this approach performed as part of the
Santa Clara Valley NPS pollution control plan
development is shown in Figure 8-1. Three BMP
categories were considered: educational (E), regulatory
(R), and public agency actions (P). Within each
category, specific BMP practices were identified (e.g.,
E1, E2) and compared to evaluate the cost and benefit
of each level. Some of the individual practices shown
on Figure 8-1 were considered but not included. This
approach is analogous to the screening step described
in Chapter 7. The complete process used in the Santa
Clara Valley study is described in the case study at the
end of this chapter.
Another example of this approach which includes
structural controls is shown in Figure 8-2 (Pitt, 1989). In
this example, 10 different urban runoff pollution
138
-------
Educational
control
measures
E1 , t
E2
E3
E4
E5
E6
E7
E8
E9
• E10
E11
E12
E13
E14
E15
E16
E17 '
E18
1
' \
k i
1 I
r 1
i
1
4
E19 '
, Considered
E20 butnot
E21 included*
E22 j
Regulatory
control
measures
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
R16
R18
R19
R20
rtt
i
H in
Considered
but not
included*
I
*
Practices in low-control alternative
Practices in medium-control alternative
Practices in high-control alternative
Removed during initial screening
Public
agency
actions
•ttt
P4 ' "
P5
P6
P7 J
P8
P9
P10
P11
P12
P13
P14
P15
P16
P17
P18
P19
P20
P21
P22
P23
P24
P25
P26
P27
P28
P29
P30
P31
P32
P33
P34
r
i r
)
r
t
Considered
but not
included*
1
Figure 8-1. Example alternative development process (Woodward-Clyde Consultants, 1989).
prevention and control practices alternatives are plotted
to compare phosphorus reduction with annual cost. The
practices analyzed include various combinations of
street sweeping, catch basin cleaning, construction of
detention basins, and implementation of infiltration
practices. Similar plots were also developed for solids
and lead removal. Based on this analysis, Program 8
was recommended, a combination of infiltration and wet
detention.
This second method is especially applicable for meeting
general goals that do not include specific pollutant
removal requirements. For example, if the goal is to
reduce nitrogen discharges to a coastal embayment by
the maximum extent practicable, then a series of
alternatives can be developed covering a,range of
pollutant reduction levels and costs. These alternatives
then can be compared on a cost-benefit and
affordability basis.
The third method of developing alternatives begins with
the screened list of appropriate control measures. Each
BMP is then assessed for its ability to address the
known and anticipated problems. As an example,
preference might generally be given to BMPs that:
• Address more than one problem or lead to meeting
more than one goal.
• Have lower construction and operating costs.
• Are most effective at removing the pollutants of
concern.
• Emphasize pollution prevention rather than treatment.
• Are likely to address future problems.
• Concentrate on addressing the priority problems.
The assessment of individual BMPs results in alternatives
based on implementing each BMP throughout the study
139
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10—1
8 —
6 —
2-
10
D
7
D
2
D
1
D
3
D
5
D
4
D
6
D
8
D
g
D
"I 1 1
10 20 30
Percent Reduction Compared to Current Program
40
Figure 8-2. Phosphorus removal for candidate control programs (Pitt, 1989).
area. The comparison of alternatives is then in effect a
comparison of different BMPs. This approach yields
useful data on systemwide implementation of particular
BMPs. While one type of BMP might not address the
range of urban runoff problems or goals in a study area,
an urban runoff pollution problem might exist which a
particular BMP is well suited to control. In this case,
implementation of that BMP on a regional basis, with
the BMPs strategically located by the municipality, can
be more effective and more easily controlled than
requiring each developer to implement that BMP for
individual developments.
An example of this method of alternative development
Is the Henrico County, Virginia, regional storm water
detention program (George and Hartigan, 1992). Early
in the process of developing a storm water management
plan, it was decided that, given the conditions existing
in the watershed, regional detention basins would be
used to control runoff pollution. Regional detention
basins were chosen because they provide both flood
and pollution control, had fewer site restrictions than
other pollution control structures, and can be designed
to accommodate expected new developments.
Therefore, the major remaining decision in the program
was the number, location, and size of the detention
basins.
All the above methods lead to the development of
alternative plans to address the urban runoff pollution
problems of concern. While the actual contents of each
alternative plan are site specific and depend on the type
of alternative evaluation to be conducted, some general
guidelines for presenting the alternative plans can help
in assessing them. Preliminary sketches, rough cost
estimates, expected pollutant removals, and
environmental effects can be included for each
alternative so comparisons can be made.
BMP Selection Process
After the alternatives have been developed, they are
compared using a decision process (Figure 8-3) that
evaluates the relative merits of each plan. Because of
the complexity of urban runoff control problems, a
number of factors must be considered in assessing
alternative plans. These alternatives are represented in
Figure 8-3 as inputs to the decision process, and
include analysis tools, design conditions, and decision
factors. The analysis tools are those used to assess and
rank the existing pollution problems (see Chapter 6).
The design conditions are the set of conditions under
which to compare the alternatives. The decision factors
are the criteria used to compare the alternatives. All
these inputs are then used to evaluate the alte -natives
using one or more decision analysis methods. This
section first describes each input to the decision
analysis, then describes the various decision analysis
methodologies that can be used to select BMPs that will
comprise the urban runoff pollution prevention and
control plan.
Analysis Tools
These tools, described in detail in Chapter 6, can
include watershed models, receiving-water models, and
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Analysis Tools
• Watershed models ^ Source flows/loads
• Water resource models *" Receiving water cone.
• Ranking models *• Priority problems
\
m
Design Conditions
• Wet-weather events
• PS/NPS flow/quality
• Receiving water flow/quality
Decision Factors
• Cost (capital, O&M)
• Program goals
• Environmental effects
• Public acceptance
• Others
Figure 8-3. Conceptual diagram of BMP selection method.
ranking models. The numerous types of models range
from simple to complex, and selection of appropriate
models to use has been discussed. The analysis tools
are used to project future conditions, given the
alternatives being investigated. For example, the total
pollutant loads for each alternative can be calculated
(whether using a unit load method or complex models
such as SWMM), yielding one item of input information
as the alternatives are compared. Similarly, the impacts
to receiving waters can be assessed using these tools,
to compare these effects before making a decision.
In the Humber River drainage area in Toronto (Figure
8-2), for example, SLAMM was used to analyze 10
different control programs (Pitt, 1989) for program cost
and pollutant removal. The final decision was based
largely on the cost-effectiveness information
determined for each of the alternatives using this
analysis tool.
Design Conditions
One major consideration in BMP selection is to
determine appropriate conditions under which to
compare the alternatives. These so-called design
conditions are generally set up to reflect various future
conditions, including future no-action conditions which
reflect future expected conditions with no new BMPs.
Some important design conditions to be developed as
part of an urban runoff pollution prevention and control
plan include:
• Population
• Land use/expected development (i.e., buildout)
• Point source/NPS flows/concentrations
• Background receiving-water flows/concentrations
Decision Analysis
• Holistic
• Cost-benefit
• Matrix
• Decision factor
«Optimization
Recommended
BMP
plan
Each condition is defined for specific future planning
periods (e.g., 20 years).
Part of the comparison involves the selection of
worst-case or critical conditions. In the case of a
receiving water, this condition could be a summer
low-flow period. In the case of urban runoff flow and
load estimation, it often involves selection of wet-
weather design conditions. These wet-weather conditions
are often in the form of design storms. For example,
runoff from a new development site might be required
to meet preexisting conditions up to a 25-year frequency
design storm. A state CSO policy might require control
up to a 1-year, 6-hour design storm. Two significant
concerns exist when developing wet-weather design
conditions. One is distinguishing between wet-weather
design criteria used for pollution control and for flood
control. The second is the use of individual design
storms versus multiple storms, continuous simulation,
or probabilistic methods.
Historically, design storms have been used to size
structures for flood control purposes. These facilities
were often sized to control storms of 5-year, 10-year,
25-year, or greater return periods. In contrast, BMPs
used for wet-weather pollution control can be sized for
much smaller storm events (e.g., 1-year storm or less),
because most rainfall events (over 90 percent) are
smaller than a 1-year storm. Thus, a BMP sized for a
1-year storm would control more than 90 percent of the
total runoff volume. Of course, many other BMP design
factors are important (e.g., retention time and peak flow
capacity), but design criteria appropriate for pollution
control should be kept in mind. This also points out the
need to consider multiple design conditions for dual
purpose (water quality and flood control) BMPs.
141
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Individual design storms have been and still are often
used to size structural BMPs. They are also frequently
specified in various federal, state, and local regulations.
While use of a design storm is a simple, understandable
criterion, deciding on the size storm is less clear cut. A
review of wet-weather design conditions stresses the
benefits of using continuous or probabilistic simulation
rather than relying on a single design storm event
(Freedman and Marr, 1992). The increasing power and
speed of personal computers allows modeling of a long
time series of rainfall-runoff conditions (using the
watershed models, and in some cases receiving water
models, described in Chapter 6) at a reasonable cost.
This method allows investigations of a large number of
storm events and the ability to develop a frequency
distribution of values of concern (i.e., number of
overflows, amount of pollutant load, or number of water
quality violations) for the range of rainfall conditions.
An example (Figure 8-4) of the use of continuous
simulation (Freedman and Marr, 1992) indicates a
frequency distribution of bacteria concentrations with
and without CSOs at a particular location. Such results
frame the range of possible CSO control effects and
help determine appropriate control goals and level of
desired reduction for a range of conditions rather than
for one event.
Decision Factors
An important step in BMP plan selection is to determine
the important decision factors. The selection of these
factors is site specific and needs to be determined by
the program team based on the characteristics of the
watershed and the financial and personnel resources
available. Typical decision factors are discussed below.
Cost
One of the most important decision factors is the relative
cost of each alternative. In cost assessment, costs of
development and implementation for nonstructural
BMPs, as well as of construction and operation for
structural BMPs, need to be considered. The program
benefits such as those associated with restored
resources also need to be considered. Costs should
generally reflect the life-cycle cost of an alternative over
the planning period and are usually easy to derive. The
cost benefits associated with the implementation of a
control plan, however, are usually more difficult to
determine. For example, if an urban runoff control plan
is designed to reduce the discharge of fecal coliform to
a closed shellfish area, monetary benefits are derived
from opening these beds. While analysis of these
benefits can be difficult, they should be included in
determining total program costs.
Meeting Program Goals
Alternatives are also assessed on their ability to meet
program goals, including the control of major sources
and effects on priority watersheds. Since at this stage
in a program, the goals have been reassessed and
expanded upon a number of times, a large number of
specific goals might exist, and each alternative might
not meet all the program goals. Preference generally is
given to alternatives that address the most goals or the
most important goals. Priority resources and pollution
sources should be the focus of the selected alternative.
Operability
The decision factors included here take into consideration
the reliability of structural controls, the reliance of the
alternative plan on existing structures, and the number
160
100 1,000 10,000
Fecal Coliform Concentration, MPN/100 mL
Figure 8-4. Example continuous simulation results (Freedman and Marr, 1992).
100,000
142
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of structures included in the alternative. Operability is
generally a measure of a system's complexity.
Complicated systems and plans might be difficult or
expensive to implement and operate; these factors are,
therefore, taken into consideration in the BMP selection.
Typically, this decision factor favors source control and
regulatory practices that do not have the level of
complexity and possible operational problems of
structural controls.
Buildability
This decision factor is directed primarily at the selection
of structural BMPs. Taking into consideration the
various aspects of construction, the criteria investigated
under this category include the site requirements, extent
of disruption, and degree of construction difficulty. When
relying on complex structural controls, difficulties
inherent in construction and future maintenance might
need to be overcome., While not a consideration in
source control and regulatory control practice, this
factor can be very important for structural controls.
Environmental Effects
Implementing urban runoff pollution control plans can
affect the environment both positively and negatively.
The positive effects on resources result from the
removal of pollution sources. Resources that can be
positively affected include water resources, aquatic
animal and plant life, wildlife, wetlands, and many
others. The negative environmental effects, which can
include aesthetic problems, cross-media contamination,
the loss of useable land, wetlands impacts, and many
others, must also be considered in the assessment.
The importance of this decision factor is becoming more
widely recognized. There seems to be a shift away from
viewing urban runoff control structures only on their
pollution control ability. Incorporating structures into
new developments or retrofitting them in existing areas
can gain wider acceptance if additional aesthetic
qualities are considered. For example, unvegetated
aboveground infiltration basins or diy ponds are
generally not attractive elements of the environment
and could serve as insect breeding grounds.
Natural-looking wet ponds or vegetated wetlands,
however, can be incorporated into the environment and
even serve to improve aesthetics. These issues can
greatly affect public acceptance.
Institutional Factors
This decision factor relates to existing governmental
structures, legal authority, and implementation
responsibilities. To implement alternatives, the logistical
resources must be in place, and the proper authority to
pass and enforce regulatory practices must exist. If the
proper authority does not exist, an analysis of attaining
it must be undertaken. In addition to these
considerations, the team should investigate existing
urban runoff programs in the community, region, or
state. Often, cost savings can be realized and total
program efforts can be reduced by taking advantage of
material and data compiled during these existing
programs.
Public Acceptance
In many instances, the public will be responsible for at
least a portion of the funding required to implement the
recommended plan. Public reaction to the urban runoff
control plan should, therefore, be assessed through the
use of public meetings. Measuring public acceptance
can be difficult, but can be important to the overall
success of a program,
Other Decision Factors
Additional decision factors—such as maintainability,
level of pollution control, or size requirements—can be
included in the assessment of alternative plans if they
are more important than those discussed above.
Once the final decision factors have been chosen and
applied to the alternative plans, the plans can be
assessed through applying a decision analysis tool.
Methods for conducting this decision analysis are
presented below.
Decision Analysis Methods
Assessing alternatives takes into account a variety of
factors, both quantitative and qualitative. The type of
assessment conducted in these programs, which
involves an integration and comparison of these factors,
is an example of multiattribute decision-making and can
be performed with various decision analysis methods.
The following decision analysis methods, which are
listed in order from the most qualitative to the most
quantitative, can be utilized:
• Holistic
« Cost-benefit ratios
• Matrix comparisons
• Decision factor analysis
• Optimization
Two additional BMP selection processes, which combine
aspects of a number of the above approaches, are
discussed in the case studies at the end of the chapter.
Holistic
This approach is qualitative and relies on certain basic
facts, intuition, and professional judgment. One key
deciding factor (e.g., cost) can guide the process. Given
143
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the inherent complexity of assessing alternative urban
runoff control plans and the large number of available
inputs to the decision, this approach is usually
over-simplified. Selecting an appropriate plan from the
developed alternatives will generally require an
assessment of multiple factors and should be done in
as quantitative a manner as is reasonably possible.
Cost-Benefit Ratios
The relative value of different alternatives can be
measured using cost-benefit ratios, such as cost per
pound of pollutant removed or cost per day of effect on
resources. This approach can be used as a tool to
determine which BMP should be used first. For
example, if it is determined that reducing solids using
source control measures costs less per pound than
using a structural BMP, then source control measures
should be utilized first Since the unit cost of source
control measures increases with the amount of solids
eliminated, the cost per pound of solids removed
increases with the number of pounds removed. The
extent to which source control measures should be
used for pollutant removal is then given by the point at
which the marginal cost-benefit ratio (i.e., change in
cost/change in benefit) becomes larger than that of
another alternative.
Another advantage of the cost-benefit ratio approach is
that it allows use of the knee-of-the curve methodology,
which seeks to determine the point in the cost-benefit
curve where the marginal cost to achieve a marginal
benefit becomes significantly higher. This factor is
measured by the marginal cost-benefit ratio defined
above. Figure 8-5 shows an example of this
methodology where the cost-effectiveness drops
dramatically as practices are implemented to reduce
lake standards exceedance to below 10 days per year.
The cost-benefit ratio approach, however, is limited by the
number of cost-benefit ratios that can be conveniently
considered simultaneously. To represent the different
elements of a complex issue better, where some benefits
might be counterbalanced by some detriments, multiple
costs and benefits must be considered.
Matrix Comparison
Matrix comparison, a common decision-making method
used in facilities planning and siting, is suggested in
EPA's Construction Grants guidelines (see Table 8-2).
Environmental impacts in Table 8-2 can be divided into
short-term construction-related impacts and long-term
operational impacts. The matrix comparison approach
is also applicable to the assessment of urban runoff
control alternatives. This approach involves preparing a
matrix that compares alternatives against selected
decision factors, both quantitative and qualitative. Where
possible, numerical values are given to compare the
alternatives, and, for qualitative factors, subjective
comparisons are used (such as poor, fair, good, and
excellent).
An example of the matrix comparison approach for CSO
abatement is shown in Table 8-3. In this example, three
alternative control programs are compared for cost,
conformance with objectives, operability, and buildability.
While Alternative 1 provides the greatest pollutant
removal and reliability, it also has the highest cost. If
cost is an important factor, Alternative 3 would be the
selected alternative, since it has the lowest present
worth cost. Alternative 2, however, provides better
reliability than Alternative 3 and has equivalent
8
U)
I
°o
i£
Annual days of water quality violation
vs.
Design storm facilities
20 30
40
50
60
70
80
Average Number of Days per Year
Lake Standards Would Be Exceeded
Figure 8-5. Example cost-benefit ratio curve (Moffa, 1990).
144
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Table 8-2. Example Matrix Comparison (adapted from U.S. EPA, 1985)
Alternatives
Type of Impact
#3
#4
Monetary Cost, $
Capital cost
Annual O&M cost
.Cost per household unit
Environmental Impact
Cultural resources
Floodplains and wetlands
Agricultural lands
Coastal zones
Wild and scenic rivers
Fish and wildlife
Endangered species
Air quality
Water quality and uses
Noise, odor, aesthetics
Land use
Energy requirements
Recreational opportunity
Reliability
Implemcntability
o
•H-
Legend:
++ Significant beneficial impact
+ Minimal beneficial impact
o No impact
- Minimal adverse impact
••— Significant adverse impact -•
cost-effectiveness in terms of present worth dollars per
gallon controlled. While this approach is useful, it can
be quite subjective and care and professional judgment
must be taken in defining the appropriate decision
factors and applying the method.
Decision Factor Analysis
This is a matrix approach, which further quantifies the
decision factors by using weighting methods. In this
approach, quantitative factors are used to eliminate the
subjective comparisons required in other matrix
approaches. These criteria should be:
1. Nondominant—no criterion should be dominant. •
2. Complete—no pertinent information should be left
out.
3. Scorable—criteria cannot be vague, since it must be
weighted clearly.
4. Independent—criteria should not overlap each other.
Weights are then generated for each decision factor.
These weights must have a common scale, and the
relative importance of each factor to the decision should
be reflected in the weights. One example of this
approach for site priority setting was described in
Chapter 6. A further example is the BMP selection
approach in the ME DEP case study at the end of this
chapter. The major difference between this approach
and the matrix approach outlined above is that, in this
approach, the decision factors must be quantitative.
Therefore, subjective comparison terms, such as good
or fair, cannot be utilized. The decision factors must be
able to be described by values that can be summed.
Variations on this type of approach and various decision
support software can facilitate the conduct of these
analyses.
Optimization
Optimization, a widely used method of quantitative
decision making, involves formulating a problem as the
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Table 8-3. Example CSO Abatement Alternative Matrix Comparison (Metcalf & Eddy, Inc., 1988)
Alternatives
Selection Criteria
#1
#2
#3
Monetary Factors
Capital cost
Annual O&M cost
Present worth (PW), 20 yr
PW, S/gal
Conformance with Objectives
Control of major discharges
Elimination of problem areas
Impact of priority areas
Operabillty
Number of facilities
Rolfability
Level of O&M
Reliance on existing facilities
Impacts on downstream facilities
Bulldabillty
Site requirements
Extent of disruption
Dagrsa of difficulty
Adaptability to phased Implementation
Conformance with current plans
$176,000,000
$162,000,000
$9.08
Good
Good
Good
0
High
Low
Low
Low
Low
High
High
Good
Fair
$106,000,000
$4,070,000
$139,000,000
$7.77
Good
Fair
Good
3
Medium
High
High
High
High
Low
High
Fair
Poor
$92,800,000
$4,080,000
$126,000,000
$7.77
Good
Fair
Good
3
Low
High
High
High
High
Low
High
Fair
Poor
maximization (or minimization) of an objective function,
subject to a series of constraints. In linear optimization,
both the objective function and the constraints must be
linear functions of the decision variables. Various
methods are available for finding the optimum set of
decision variables and several software packages can
perform the analysis. These methods are summarized
in basic textbooks on optimization (Monks, 1987).
For plan selection, the objective function can be cost or
a more complicated function of cost, benefits, and
detriments. Examples of benefits that could be included
are gallons of discharge removed, pounds of pollutants
removed, and days of beach closure avoided. A
multifactor objective function can account for tradeoffs
among costs, benefits, and detriments by incorporating
relative weight for each factor:
where:
F = objective function
a) = weight and conversion factor
yi = cost-benefit factor
All terms in the above equations must have the same
dimension (e.g., dollars) so that weights also
incorporate a conversion factor. The optimization
process then consists of maximizing the objective
function, by optimally selecting the values of the
decision variables on which the different factors
depend. Then, each cost-benefit factor, y|f must be
expressed linearly in terms of each of the decision
variables, X:
where:
by = a different weight or conversion factor
This relationship is relatively easily established for cost
(such as Hfe-cycle cost), but more difficult for other
factors, such as pounds of pollutant removed or days of
beach closure. For these types of factors, models need
to be applied with different values of the decision
variable and straight-line fitted to the result. Constraints
must also be established as linear functions of the
decision variables. Possible constraints are the
maximum number of excursions of standards per year
or the maximum amount of pollutant reduction
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achievable given background conditions. Once the
objective function and constraints are defined, various
algorithms and software packages are available to
determine the combination of decision variables
maximizing the objective function.
A major problem with this approach is that many
relationships pertaining to BMP selections are
nonlinear. Qualitative factors are also difficult to
incorporate in the process, especially in the form of
linear functions of the decision variables. Nonlinear
optimization, while accounting for the nonlinear
dependence of various factors, is mathematically
complex. It also tends to suffer from the same types of
drawbacks as linear programming because it is not
effective for problems that include qualitative factors.
Determination of Appropriate Decision
Analysis Approaches
Matrix comparison and decision factor analysis
approaches are typically best suited to BMP selection.
Such approaches rely on the analytical tools available
to analyze the system and on the best professional
judgment of those assessing the alternatives. Given
specific problems that can be quantified, optimization
could be tried. Most BMP selection projects involving
urban runoff, however, would be too complex. If the
problems being addressed are simple, then the holistic
or cost-benefit ratio techniques can be utilized. These
simple, qualitative approaches can also be implemented
as first approximations for plan assessments whose
final results must be made using more complex
approaches. In summary, an appropriate decision
analysis method or methods must be selected that
reflect:
• The complexity of the problems and the plans to
address them.
• The data needs of each method and the ability to
obtain the required data.
• The financial and personnel resources available to
conduct the assessment.
A matrix comparison or decision factor analysis most
likely would be involved.
Conclusions
The selection of BMPs to control urban runoff pollution
is difficult and can best be performed by undertaking a
systematic assessment process, aided by the use of
analytical tools and the selection of appropriate design
conditions and decision factors. Because of the
qualitative nature of some inputs to the decision,
subjective comparisons among the alternative plans
typically are necessary. The process outlined in this
chapter is a guide for decision making, but cannot
account for all possible circumstances. Professional
judgment and care are needed in determining the
methods for developing alternatives, the decision
factors to be employed, and the decision analysis
method to utilize. Once these choices have been made
and the BMP plan has been selected, the urban runoff
pollution prevention and control plan can be developed
in more detail so that it can be implemented.
The following case studies provide examples of BMP
selection approaches used by the State of Maine for
runoff control in new developments and by the Santa
Clara Valley Water Quality Control Board in the
development and implementation of a major runoff
pollution prevention and control plan.
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Case Study:
Maine Department of Environmental Protection
BMP Selection Matrix
To address storm water and NPS pollution control in areas of new development, the Maine Department
of Environmental Protection (ME DEP) has developed a method to select BMPs. The method which is
presented in a state guidance document is based on the following information:
• Development land use type and size
• Receiving-water type (e.g., estuary, wetland, river, or stream)
• Watershed priority (either priority or non-priority)
• Erosion and sediment control target or level to achieve
• Storm water quality control target or level to achieve
• Erosion and sediment control options and treatment level codes
• Storm water quality control options and treatment level codes
To implement the BMP selection method, ME DEP developed a series of eight matrices, two matrices
for each receiving water type (i.e., estuary, wetland, river, and stream). One matrix is applied to
development in designated priority watersheds and the other is applied to development in nonpriority
watersheds. A priority watershed list has been developed by ME DEP based on environmental sensitivity,
local support for water quality, and importance of the watershed to the state. Example matrices for priority
and non-priority estuary watersheds are shown in Tables 8-4 and 8-5.
Each matrix has two major components, which are broken down by land use type: an erosion and
sediment control level to achieve and a storm water quality level to achieve. The level to achieve for a
given combination of land use and receiving-water category is a relative, qualitative measure of the
impact of storm runoff pollution. It ranges from 1 to 5, with 1 being the lowest impact and 5 being the
greatest impact. For example, a multihousing development proposed for a priority estuary watershed is
given an erosion and sediment level to achieve of 2 and a water quality level to achieve of 3. By
comparison, a small residential development in the same priority watershed is given an erosion control
level to achieve of 1 and a water quality level to achieve of 1. In all cases, the levels to achieve for
priority watersheds are greater than or equal to those for nonpriority watersheds.
Each matrix also addresses the types of BMPs that can be implemented for pollution control. ME DEP
selected a number of BMPs and assigned each a treatment level code based on the expected level of
pollutant removal. The treatment level code is a relative, qualitative measure designed to indicate the
relative pollutant removal expected from various BMPs. Treatment level codes range from 1 to 3, with 1
providing the lowest level of control and 3 providing the greatest level of control. The BMPs and their
treatment level codes are shown in Table 8-6. As indicated, various designs for each BMP are given
different treatment level codes. For example, a 50-foot buffer is given a treatment level code of 1; a 125-foot
buffer is given a treatment level code of 2; and a 200-foot buffer is given a treatment level code of 3.
For a proposed development to be approved, the sum of treatment level codes for the proposed BMPs
must be greater than or equal to the level to achieve. For example, if a multihousing unit development
is proposed for a priority estuary (erosion level to achieve of 2 and water quality level to achieve of 3),
the developer could implement erosion and sediment controls (treatment level 2) and a combination of
a swale (treatment level 1) and an infiltration system (treatment level 2). Additional combinations also
could be implemented as long as the total treatment level provided is greater than or equal to the total
level to achieve. ME DEP has also recommended that at least one vegetative BMP be implemented
unless the site is already 100-percent impervious. The specified vegetative BMPs are buffers, grassed
swales with level spreaders, and swales.
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Table 8-4. Priority Estuary Storm Water Control Matrix
Land Use Category
Low-density residential, >2 ac/lot
High-density residential, <2 ac/lot
Erosion and
Sediment
Level to
Achieve
1
2
Erosion and
Sediment Controls
Erosion and
sediment 1
Erosion and
sediment 2
Water Quality
Level to
Achieve
1
3
Storm Water Controls
Buffer 1
Buffer 1 or 2
Wet pond 2
Commercial, <1 ac disturbed
Commercial, 1-3 ac disturbed
Commercial, >3 ac disturbed
Intensive-use open space
(e.g., golf courses, nurseries)
Multihousing users
Erosion and
sediment 1
Erosion and
sediment 1
Erosion and
sediment 2
Erosion and
sediment 2
Erosion and
sediment 2
Infiltration 1 or 2
Created wetland 2
Buffer 1
Buffer 1 or 2
Infiltration 1
Swale 1
Buffer 1 or 2
Infiltration 1 or 2
Created wetland 2
Wet pond 2 or 3
Fertilizer control 1
Shallow impoundment 1
Buffer 1 or 2
Fertilizer control 1
Pesticide control 1
Created wetland 2 or 3
Wet pond 2 or 3
Buffer 1 or 2
Fertilizer control 1
Pesticide control 1
Created wetland 2
Wet pond 2
Infiltration 1 or 2
Industrial, <1
Industrial, 1-3
Industrial, >3
ac disturbed
ac disturbed
ac disturbed
1
1
2
Erosion and
sediment 1
Erosion and
sediment 1
Erosion and
sediment 2
1
2
5
Buffer 1
Swale 1
Buffer 1 or 2
Swale 1
Buffer 1 or 2
Swale 1
Created wetland 2
Wet pond 2 or 3
or 3
This BMP selection system is in its early stages of implementation. Its success will depend on the ability
to establish levels to achieve that adequately protect water bodies in new developments. It will also
depend on the ability of treatment level codes to quantify the effectiveness of the identified control
measures. Thus, the system is a technology-based approach for erosion and sediment control, as well
as for storm water pollution control.
Currently this method is outlined in a statewide guidance document and is not a regulatory requirement.
Municipal officials can incorporate this process at their discretion in subdivision regulations. This method
of BMP selection requires extensive upfront work to develop the matrices and BMP levels of treatment.
Once these are developed, however, this method provides a simple and direct technology-based
approach to BMP selection. It has flexibility in terms of the range of BMPs that can be selected for given
types of proposed development and given site constraints.
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Table 8-5. Nonprlorlty Estuary Storm Water Control
Erosion and
Sediment
Level to
Land Use Category Achieve
Low-density residential, >2 ac/lot 1
High-density residential, <2 ac/lot 2
Commercial <1 ac disturbed 1
Commercial, 1-3 ac disturbed 1
Commercial, >3 ac disturbed 2
Intensive-use open space 2
(e.g., golf courses, nurseries)
Muilihouslng units 2
Industrial, <1 ac disturbed 1
Industrial, 1-3 ac disturbed 1
Industrial, >3 ac disturbed 2
Matrix
Erosion and
Sediment Controls
Erosion and
sediment 1
Erosion and
sediment 2
Erosion and
sediment 1
Erosion and
sediment 1
Erosion and
sediment 2
Erosion and
sediment 2
Erosion and
sediment 2
Erosion and
sediment 1
Erosion and
sediment 1
Erosion and
sediment 2
Water Quality
Level to
Achieve Storm Water Controls
1 Buffer 1
2 Buffer 1 or 2
Infiltration 1
1 Buffer 1
1 Buffer 1
2 Buffer 1 or 2
Infiltration 1
Swale 1
Shallow impoundment 1
3 Buffer 1 or 2
Infiltration 1 or 2
Fertilizer control 1
Created wetland 2
Wet pond 2
2 Buffer 1 or 2
Infiltration 1
1 Buffer 1
Swale 1
2 Buffer 1 or 2
Swale 1
4 Buffer 1 or 2
Swale 1 or 2
Created wetland 2 or 3
Wet pond 2 or 3
Table 8-6. Summary of BMP Treatment Level Codes
BMPs
Erosion and Sediment Control
One line of erosion control
Two lines of erosion control
Nongrassed Buffers
50ft
125ft
200ft
Infiltration Systems
Single system
Multiple systems
Wet Ponds
Single-pond system holding 2.5 in of runoff
Double-pond system each pond holding 2.5
Created Wetlands
Single created wetland
Two created wetlands
Other BMPs
Swales
Shallow impoundments
Street cleaning
Fertilizer application control
Pesticide use control
Grassed swales with level spreaders
in of runoff
Reverting land (i.e., allowing currently impervious land to be a
vegetative buffer)
Level of Treatment
1
2
1
2
3
1
2
2
3
2
3
1
1
1
1
1
1
1
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Case Study:
Santa Clara Valley, California,
Nonpoint Source Control Program BMP Screening Procedure
Background
In 1986, the San Francisco Regional Water Quality Control Board developed a basin plan for San
Francisco Bay which involved regulatory activities to control point and nonpoint source discharges. The
basin plan was the driving force behind initiating the Santa Clara Valley Nonpoint Source Control
Program. This program involves a number of local governments and county agencies and is designed
to address water quality problems in Lower South San Francisco Bay. In developing the Santa Clara
Valley Nonpoint Source Plan, a 12-step process that closely follows the process outlined in this handbook
was used. The steps in this process are:
• Initiate program
• Determine existing conditions
• Conduct field monitoring
• Define program objectives
• Develop evaluation and planning criteria
• Compile inventory of candidate controls
• Apply criteria to screen candidates
• Apply professional judgment to select a practical set of controls
• Estimate overall program cost and effectiveness
• Revise the previously defined control programs to balance cost, effectiveness, and other factors
• Describe the roles of various agencies
* Develop an implementation schedule
Development of the Santa Clara Valley Nonpoint Source Control Plan began in 1986 and has continued
through various stages to initial implementation and preliminary assessment of effectiveness.
Watershed Description
Santa Clara County, which incorporates the entire study area, is located at the southern end of San
Francisco Bay (see Figure 8-6). The 690-square-mile watershed consists primarily of the relatively flat
Santa Clara Valley. Land use in the watershed is approximately 30 percent residential, 5 percent
industrial (predominantly light industry associated with high technology manufacturing), and 62 percent
open space. Three large cities—San Jose, Sunnyvale, and Santa Clara—account for the majority of
urban areas in the watershed.
Overview of Water Quality
To characterize existing water quality in Lower South San Francisco Bay, a comprehensive monitoring
program was undertaken. This program included, hydrologic monitoring, wet- and dry-weather water
quality monitoring, sediment monitoring, and biological monitoring. The monitoring was conducted
primarily to determine the levels of toxic pollutants, such as heavy metals and pesticides, as well as
nutrients and fecal coliform bacteria. Data obtained through this monitoring program were input to data
bases and used for developing computer models. Watershed loads were estimated using the Storm
Water Management Model (SWMM), calibrated to the observed data gathered in the monitoring program.
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Legend
— Santa Clara County boundary
Approximate watershed and
study area boundary
Figure 8-6. Santa Clara Valley watershed.
The data were also used to compare the relative contributions of point (e.g., waste water treatment
plants) and nonpoint source pollution to the bay.
Water quality monitoring results indicated that heavy metal concentrations in receiving waters increase
during wet weather, because of contaminated runoff as well as resuspension of contaminated sediments.
The metals primarily detected were cadmium, chromium, copper, lead, nickel, and zinc. Copper was the
primary metal regularly detected at levels greater than the EPA aquatic life criteria; these criteria were
exceeded only occasionally for cadmium, lead, and zinc. Also, during wet weather, hydrocarbons and
pesticides were detected in approximately 25 percent of the ambient water samples collected, while
none were detected during dry weather. The limited bacteria data gathered indicated increased levels
152
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(by a factor of about 10) of fecal coliform bacteria during wet weather as compared to dry-weather
conditions.
In comparing point and nonpoint source contributions to water quality problems in Lower South San
Francisco Bay, the monitoring results showed that point sources account for approximately 98 percent
of the nutrient load. Nonpoint sources, however, accounted for 60 to 80 percent of the load for metals
and about 98 percent of the total suspended solids yearly load.
Management Practice Screening
Because of the large size of the watershed and the variety of pollutants entering the Lower South San
Francisco Bay, the emphasis of the nonpoint source pollution control program was on pollution prevention
measures and nonstructural controls that could be implemented across municipal boundaries. Selection
of appropriate pollution prevention measures and controls was accomplished through a process
consisting of preliminary screening followed by final control measure selection (see Figure 8-7).
In order to screen the extensive list of potential pollution prevention and control practices, the program
team first listed important criteria for the selected measures. The criteria developed for this project were:
• Pollutants controlled: Controls for metals, pesticides, oil and grease, bacteria, and sediments are
emphasized.
• Effectiveness: Each control measure should provide sufficient pollution control toward the overall
program to warrant its inclusion.
• Reliability/sustainability: Control measures should be effective over an extended time period and be
able to be properly implemented over time.
• Implementation cost: Control measures with low planning, design, land acquisition, construction, and
equipment acquisition costs were emphasized.
• Continuing costs: Emphasis was placed on control measures with low operation, maintenance, repair,
support service, and equipment replacement costs.
• Equitability: Controls were evaluated regarding the degree to which costs and benefits would be
equitably distributed among the participating agencies.
• Universality: Controls were evaluated in terms of how universally they would have to be applied to
be effective.
• Public acceptability: Control measures were assessed on the expected public response to
implementation.
• Agency acceptability: Control measures were evaluated on the expected response of agencies
responsible for implementation.
• Relationship to regulatory requirements: Control measures were evaluated on their consistency with
existing and anticipated regulatory requirements.
• Risk/liability: Control measures were evaluated in terms of the risks or liabilities which could occur
in implementation.
• Environmental implications: Control measures were evaluated regarding the positive and negative
environmental impacts resulting from their use.
Once the control measure criteria were developed and agreed upon, the program team developed a
comprehensive list of potential measures for implementation. The inventory of potential measures was
developed through a review of technical literature and other nonpoint source control programs. In
addition, technical and managerial personnel from other state agencies, county agencies, and city public
works and planning agencies were interviewed.
153
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154
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This review resulted in a list of more than 120 separate measures to be screened. This initial list was
to be comprehensive; no consideration was given to the applicability of the measures. Once the list had
been developed, however, obviously inappropriate measures were eliminated—primarily those designed
to address specific situations that did not exist in the watershed. This initial screening reduced the list
of potential pollution prevention and control measures to 92.
This list of 92 measures was then assessed qualitatively using the criteria developed earlier in the
program. Each potential control measure was assigned a letter grade (A through F) for its ability to meet
the criteria. Measures receiving an A were viewed to meet all or a large number of the assessment
criteria, while those receiving an F were viewed to meet none or very few of the assessment criteria.
The control measures that fell into the category of F were immediately eliminated from further
consideration in the Santa Clara Valley watershed.
The final list of potential pollution prevention and control measures was then arranged into three groups
by grade, function, and implementation method as shown in Figure 8-7. The control measures arranged
by function included source controls, hydraulic controls, and treatment-based controls. The control
measures arranged by implementation method included educational controls, regulatory controls, and
public agency actions. By arranging the controls in these various ways, the program team could select
control measures that gave a good mix of type and implementation method.
Management Practice Selection
At this point, the assessment criteria used in the initial screening were applied to each potential control
measure to develop three alternative programs: Program I, the smallest scale program, was designed
to be low cost and provided a minimal level of pollution control. Program III, the largest scale program,
was designed to provide a high level of pollution control but had a high cost. Program II, designed to
represent a middle road between Programs I and III, was the program recommended in the report
because it was felt to provide the best cost-benefit of the three alternatives.
The recommended alternative included educational, regulatory, and public works (structural) control
measures. Most of these measures are to be implemented across the watershed, but some
recommendations specific to known problems areas are also included.
Implementation
In order to efficiently implement the NPS control plan, the task force determined high-priority actions for
immediate implementation. The following actions are considered to be high priority because they can be
implemented across the watershed.
• Conduct wet-weather monitoring.
• Develop and implement a public information program.
• Develop and begin implementation of illicit connection identification and removal.
• Conduct illegal dumping monitoring program and provide training.
• Evaluate treatment based controls.
• Develop and begin implementation of areawide and community-specific storm water management
program.
Still in the early stages of implementation, the program cannot yet be evaluated. Implementation of many
of the above high-priority measures, however, is progressing. This case study shows a qualitative
selection process that utilizes a set of screening and selection criteria to develop low, medium, and high
pollution prevention and control alternatives.
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References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
Freedman, P.L., and Marr, J.K. 1992. Design conditions
for wet weather controls. Proc. Water Environment
Federation Specialty Conference, Control of Wet
Weather Water Quality Problems. Indianapolis, IN.
May 31-June 3.
George, T.S. and J.P. Hartigan. 1992. Regional
detention planning for stormwater management:
model for NPDES management programs. Proc.
Water Environment Federation Specialty Conference,
Control of Wet Weather Water Quality Problems.
Indianapolis, IN. May 31-June 3.
Metcalf & Eddy, Inc. 1988. Lower Connecticut River
phase II combined sewer overflow study.
Massachusetts Division of Water Pollution Control.
Metcalf & Eddy, Inc. 1989. Coastal nonpoint source
demonstration project: nonpoint source control for the
watershed of Snell Creek—Westport, Massachusetts.
Massachusetts Department of Environmental Protection.
Moffa, P. 1990. Control and treatment of combined
sewer overflows. New York, NY: Van Nostrand
Reinhold.
Monks, J.G. 1987. Operations management: theory and
problems, 3rd ed. New York, NY: McGraw-Hill.
Pitt, Robert. 1989. Source Loading and Management
Model: an urban nonpoint source water quality
model—volume): model development and summary.
University of Alabama, Birmingham.
U.S. EPA. 1985. U.S. Environmental Protection Agency.
Construction grants 1985. EPA/430/09-84/004. U.S.
EPA Office of Water. Washington, DC.
Woodward-Clyde Consultants. 1989. Santa Clara
Valley nonpoint source study. Santa Clara Valley
Water District.
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Chapters
Implement Plan
The final step in the planning process is to develop an
implementation plan for prevention and control of urban
runoff pollution. This plan sets forth the recommended
control program in a form readily usable by the team
charged with program implementation. The information
obtained through the earlier tasks of assessing existing
conditions, collecting and analyzing additional data,
identifying and assessing problems, and screening and
selecting BMPs must be clearly summarized as a
"roadmap" or work plan for future activities.
Contents of an Urban Runoff Pollution
Prevention and Control Plan
The urban runoff pollution prevention and control plan
should contain the following information:
• Conceptual information on recommended BMPs
• Schedule of activities
• Responsibilities for BMP implementation
• Description of monitoring plan
• Summary of regulatory requirements
• Public involvement program
• Identification of funding sources/mechanisms
Each item is important to implementation of the plan and
is described in the following pages. At the end of this
chapter, a case study using the Pipers Creek watershed
implementation plan shows how each of these plan
components was developed.
Description of Recommended Best
Management Practices
The first part of the urban runoff pollution prevention and
control plan is a description of the BMPs selected for
implementation. This includes regulatory BMPs,
municipal practices, structural BMPs, and any other
BMP activities selected for implementation.
Regulatory BMPs
Regulatory BMPs, which play an important role in urban
runoff pollution prevention and control, should be
included and summarized in the control plan. The
summary requires a clear description of the proposed
regulatory changes and the approach to implement the
changes. Regulatory BMPs can address requirements
for an entire community or can be focused on a specific
area targeted for protection. The level of effort
necessary to implement the control program varies
depending on these regulatory requirements. This
information is included in the BMP description along
with a discussion of the method required to comply with
the regulation, and any required enforcement and
maintenance activities. Some regulations require
passage through the vote of a specific board or
committee, while others require a full vote of residents
in the community. The process needs to be outlined in
the urban runoff pollution prevention and control plan.
Finally, costs need to be developed. These include
one-time costs associated with implementing the
regulation as well as recurring costs associated with
education, information, oversight, and enforcement.
Case studies of regulatory control approaches are
presented at the end of Chapter 4 (Lewiston, Maine)
and Chapter 7 (Austin, Texas).
Municipal BMPs
Municipal BMPs include the nonstructural and source
control practices carried out by each responsible public
entity—street-sweeping, catch basin cleaning, and
cross-connection identification and removal. For each
of these BMPs, a plan needs to be prepared that details
the frequency of conducting each practice, the locations
at which the practice takes place (preferably on a map),
a schedule of activities, the required staffing, and the
cost. Initial program startup costs could include training
staff and purchasing equipment. In addition, municipal
BMPs typically include ongoing operational costs—
labor for public works and maintenance staff efforts. A
record system should also be designed to track
activities and pertinent data (e.g., pounds of debris
removed and areas swept). Municipal source control
and nonstructural practices are discussed in Chapters
4 and 7 and in the Lewiston, Maine, case study, which
is presented at the end of Chapter 4.
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Structural BMPs
Structural BMPs eventually require engineering design
and construction. At this stage of planning, information
needed to support each BMP includes a description,
pictures, diagrams or concept sketches (see Figures
9-1 and 9-2), design information and assumptions, as
well as pertinent conceptual details of the structural
BMPs. The details should indicate known site conditions
such as existing structures; topography; and other
site-specific information such as soil conditions, utility
locations, and wetlands, as available. Also included
should be a general plan of the watershed showing
Influent sluice gate
Inclined
find screens
over effluent
cninool—\
54-in conduit to outfall
V
Collection trough -
42-in Influent conduit
Dewatering system
Sluice gate and
target baffle
NaOCI storage
and feed system
Effluent
channel
Overflow
weir
Slope 1/4 in/ft
Detention tanks
Operations building
- Influent channel
Figure 9-1. Example CSO control conceptual design of a sedimentation/disinfection facility (Metcalf & Eddy, Inc., 1988).
Winter
flow weir
Parking lot
surface
Riprap lined inlet
channel/level spreader
12 in deep, 4 ft wide-.
Approximate
existing ground
Additional storage
volume, 0.5 in
Dewatering
outlet pipe
Dewatering manhole
4-In perforated PVC underdrain
S = 0.2%
Washed stone, 3/4 to 1 1/2 in
Min. depth of sand layer, 12 in
Impermeable geomembrane liner
Figure 9-2. Example runoff control conceptual design for a filter system (U.S. EPA, 1992).
158
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locations of the recommended BMPs and the pollution
sources they are designed to address. Final detailed
design plans and specifications for each structural BMP
are developed later, once the plan is approved.
For each BMP, a cost estimate is also developed. After
the initial cost estimate during the alternatives
development step, this estimate is refined to a more
detailed estimate for purposes of the implementation
plan. Improved accuracy is important since it could
provide a basis for allocation of funds. Given the
uncertainty at this stage (site survey and engineering
work normally is still to be done), contingencies should
be included in the estimate; and the cost perhaps
should be presented as a range. For structural BMPs,
ranges of costs can be obtained by consulting the
Chapter 7 references. These costs, however, provide
only guidelines and often vary widely depending on
site-specific characteristics, such as soil conditions,
depth to bedrock, and level of surrounding development.
Costs include those for design, capital, and operations
and maintenance. Costs for engineering, field surveys,
borings, construction labor and materials, and
contingency are also usually included. These costs can
be presented in terms of present worth and tied to an
applicable price index, such as the Engineering News
Record (EN R) cost index, so the costs can be adjusted
by others in the future.
Proper operation and maintenance is particularly
important to the long-term functioning of structural
BMPs. A method must be developed for ensuring that
maintenance requirements are included in the
management plan along with inspection and/or
enforcement mechanisms. For example, if a community
requires an industry or developer to construct a
detention facility to remove suspended solids from
runoff, the community must also develop a method for
ensuring that the practice is properly maintained. Some
municipalities have addressed this issue by establishing
special funds designed to ensure maintenance of
BMPs. In these circumstances, a municipality might
require the industry or developer to contribute a fee to
a fund that pays for inspection and maintenance of the
BMP by municipal employees. Another option is for the
municipality to require the private party to perform the
maintenance. This option, however, gives the
municipality less control over the BMP and still requires
that the municipality conduct periodic inspections of the
BMPs.
Other Related Activities
Several related activities, which might not fall strictly into
the earlier categories identified, include public participation
and education, monitoring, and maintenance and
enforcement. Both public participation and education,
and monitoring are addressed as separate plan
components later in this chapter. Maintenance and
enforcement is discussed under the section on
responsibilities for BMP implementation. In general,
however, all BMPs and activities which are to be
included in the program should be described and
discussed as part of the implementation plan.
Schedule of Activities
Because of the complex nature of urban runoff planning,
implementing all the recommended BMPs in a short
time generally is not possible. In some cases, the
implementation schedule must allow time for pilot
testing of BMPs in selected areas, monitoring the
results of these pilot tests, and final desigo of full-scale
BMPs. In fact, implementation of complex and
expensive urban runoff BMPs is often conducted in a
series of steps. These steps can include the following
(U.S EPA, 1991):
• Planning phase: Analyzing, evaluating, and planning
initial tasks.
• Preparation phase: Preparing budgets, resources,
and necessary permits.
• Pilot-scale implementation phase (only if necessary):
Testing selected BMPs for effectiveness and cost
prior to full-scale implementation.
• Full-scale implementation: Designing and constructing
the selected BMPs.
• Evaluation/documentation phase: Evaluating the
effectiveness of the implemented BMPs to guide
future action; preparing periodic reports documenting
the results.
These considerations are incorporated into a schedule
with start and finish dates for major tasks and
milestones. The schedule should also include interim
dates of reporting BMP results and monitoring program
results.
Depending on the program's size, the schedule could
be shown by means of a simple bar chart or a more
complex critical path method (CPM) system using
project scheduling/management computer software.
The type of schedule selected depends on the level of
program complexity—the number of tasks and subtasks
(activities) required, the number of involved entities, the
length of time over which the program will extend, and
the available program management resources.
Implicit in developing an implementation schedule is the
need to set priorities. The program team should review
the recommended BMPs and determine an order of
implementation (or phasing), taking into account
extenuating circumstances in any particular case. If
funding is a major issue, for example, the least
expensive recommendations can be implemented early
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in the process. Individual projects need to be phased in
accordance with available funding.
One set of priorities that might be considered is to first
implement regulatory and nonstructural controls, then
evaluate them over time, and later implement structural
controls. This approach might be effective in developing
areas where BMPs can be required as development
occurs. In addition, nonstructural and regulatory BMPs
are less costly to implement than structural BMPs. This
approach would not be as effective in areas where
retrofit of BMPs is necessary. In general, priorities and
thus the schedule of program implementation, must be
tailored to each situation.
If the development of public support for the program is
critical, the team might choose to address BMPs with
potential for significant pollution reduction. In this case,
BMPs that could improve the water quality of widely used
water bodies should be implemented, if possible, before
other steps are taken. These decisions should be
reflected by the implementation schedule. A cost-benefit
analysis (see Chapter 8) can be used to assist in setting
priorities. For example, an analysis could be performed
to determine total cost per pound of pollutant removed
and projects implemented accordingly.
Responsibilities for BMP Implementation
The individuals and entities responsible for implementing
each aspect of the program must be identified in the
urban runoff pollution prevention and control plan. Since
a well-defined institutional framework for urban runoff
pollution prevention and control might be lacking, much
of the effort for implementing plans must come from local
and regional governments. Officials at the state and
federal levels will likely be responsible for enforcement
and oversight, and technical and financial assistance
might also be available.
To develop a plan, municipal officials must coordinate,
initiate activities, and motivate others in the community
or other agencies to get involved. Figure 9-3 is an
example format showing recommended actions and the
agencies charged with implementation. Obtaining firm
commitments from these agencies prior to program
Implementation is important to the final success of the
program. Table 9-1 identifies groups, agencies, and
Individuals that can provide support for aspects of the
management plan, including monitoring, design,
permitting, regulations, public education, maintenance,
and enforcement.
Description of Monitoring Plan
A monitoring program should be conducted during and
after urban runoff pollution prevention and control
program implementation to assist the municipality in
determining the effectiveness of its overall program in
achieving water resource goals. Monitoring during
program implementation includes data collection to
measure the overall program effects on water resources
and determine the effectiveness of BMPs. Existing
water resource conditions determined during the
planning process provide a good understanding of
water resource quality before program implementation.
A monitoring plan to assess water resource conditions
during and after program implementation allows the
level of resulting improvements to be assessed by
comparison to existing conditions.
Trend analyses are important in understanding the
effects of watershed activities on water resources, and
can provide important feedback to assessments of the
success of urban runoff pollution prevention and control
measures. Long-term data can be used to demonstrate
the influence of program activities on water resource
quality. Sampling data can also be used to educate the
public on the effects of urban runoff pollution on water
resources and the need for control. To increase public
awareness, information that identifies the effects of
urban runoff pollution can be disseminated in
newsletters, at public meetings, or by other means.
Overall program effectiveness can usually be
determined more easily than the effectiveness of
individual BMPs. As part of the urban runoff control
program, a long-term monitoring plan should be
designed to measure program effectiveness and
provide program accountability. The plan should use
existing monitoring stations (both those used in
previous studies and those used for collecting additional
data as outlined in Chapter 5) to collect long-term data
with which comparisons can be made. In this way, the
progress of the program in addressing pollution
problems and preventing further water resource
degradation can be determined. Monitoring plan
components (e.g., a map of monitoring stations, a
record of the frequency of sampling at each station, a
parameter list, and a QA/QC project work plan) should
be identified in a work plan similar to that outlined for
sampling in Chapter 5.
Collecting sufficient data to clearly demonstrate BMP
effectiveness is difficult for many reasons, including the
variability of runoff flow and quality, and the difficulty in
separating the effect of a particular BMP on a receiving
water. Caution should be exercised in developing these
types of monitoring programs because they can be very
expensive; sufficient data to reach a conclusion might
not be obtained. More detailed discussions of BMP
effectiveness sampling is available elsewhere (U.S.
EPA, 1976).
The effectiveness of nonstructural and regulatory BMPs
is difficult to assess. These BMPs are usually
implemented slowly over time and affect a geographically
wide area (typically within a political boundary). Patience
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Recommended Areawide NPS Control Measures (Program II)
Cities
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Table &-1. Potential Implementation Responsibilities
Program Component Potentially Responsible Parties
Other Potentially Involved Parties
Monitoring
Engineering design
Permitting and regulatory controls
Public education
Maintenance
Enforcement
Local boards of health
State water pollution Control agency
State marine fisheries department
Local engineering department
State department of public works
SOS
Local boards of health
Local conservation office
Local planning board
EPA
State water resources agency
Federal coastal zone management
U.S. Army Corps of Engineers
Regional environmental agency
Local environmental groups
Watershed associations
State environmental agency
Soil and water conservation districts
EPA
Local department of public works
SCS
Private owners of BMPs
Local conservation agency
Local board of health
Planning board
Local code enforcement officer
Federal coastal zone management
U.S. Army Corps of Engineers
EPA
Local environmental groups
University students
Volunteer organizations
Environmental consulting companies
University engineering departments
Engineering consulting companies
Local environmental groups
Environmental consulting companies
Local environmental groups
Local civic groups
Private organizations
Cable TV/newspapers
Contract maintenance providers
rating system can be useful to assess program
effectiveness semiquantitatively over time, or at critical
periods before and after BMP implementation.
These types of nonconventional monitoring methods
are not as direct as demonstrable water resource quality
improvements, but they are valuable in documenting
program success.
Summary of Regulatory Requirements
Regulatory issues that need to be addressed include
both the implementation of regulatory BMPs and the
application for regulatory approvals and permits needed
to implement nonstructural and structural BMPs.
Regulatory BMPs are discussed in Chapter 7. The
urban runoff pollution prevention and control program
could involve the modification or strengthening of
existing regulations, including zoning, site plan review,
subdivision, or wetlands protection or the development
of new regulations.
In addition, a municipality must obtain appropriate
regulatory approvals and permits before implementation
and construction of BMPs that could alter wetlands,
waterways, or water quality, even if the BMP results in
environmental benefit. These requirements should be
summarized as part of the urban runoff pollution
prevention and control program. Coordination with
appropriate agencies is advisable before applying
necessary approvals and permits. Agencies from which
permits will be required should be contacted early in the
planning process to determine requirements for
securing all necessary approvals and permits.
Major permits required in implementing urban runoff
control BMPs originate at all levels of government-
federal, state, and local. The permits of concern usually
address the following issues:
• Alterations to wetlands.
• Dredging and filling operations.
• Disturbances within a specified distance of a
waterway.
• Soil and erosion control at construction sites.
• Alterations to the water quality of a water body.
• Alterations to existing or construction of new
discharges to a water body.
• Impacts on endangered species.
• Impacts on historic/archaeological sites.
• Impacts on natural resources and ecologically sensitive
areas.
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Major permitting programs at the federal level include:
the National Environmental Policy Act (NEPA); the U.S.
Army Corps of Engineers—Section 10 of the Rivers and
Harbors Act and CWA Section 404; EPA's NPDES
Permit Program; and the CZMA Federal Consistency
Concurrence Certificate. Additional requirements can
be in place for many of the regulatory programs outlined
in Chapter 2. Information is available through regional
EPA offices and the state agencies dealing with these
issues. Requirements for state and local permits are site
specific vary widely, and are available from the
responsible local or state agency.
Public Involvement
Support and involvement of the general public, both
homeowners and businesses, is considered crucial to
plan implementation and its ultimate success. While
public involvement should be an integral part of the
planning process, a public involvement program should
be developed as part of overall program implementation.
Components of public involvement programs can be
wide ranging, involving one or more of the following
components:
• Program meetings and presentations to provide
information and updates.
• Program materials such as newsletters, fact sheets,
brochures, and posters.
• School education programs such as special classes
and tours.
• Homeowner education programs on individual control
of urban runoff related pollution.
• Consumer education programs on appropriate
product purchasing and handling.
• Business education programs.
• Media campaigns including radio, newspaper, or
television.
• Coordinating and coalition building with local
watershed or activist groups to support the program.
The numerous other possibilities include setting up a
program hotline, sponsoring special events, and
conducting surveys. A task force can be set up to
coordinate and help focus these activities.
Public involvement can be approached in numerous
ways. The case study on the Pipers Creek watershed
at the end of this chapter identifies the elements used
for that program. The Santa Clara Valley case study at
the end of Chapter 8 shows how public involvement
activities can be identified and evaluated as BMP
options.
Funding Sources and Mechanisms
Since a large percentage of funding for urban runoff
pollution prevention and control programs comes from
local sources, this section focuses on local funding
mechanisms. Sources of funding at the federal and
state levels are uncertain and likely only to provide a
small percentage of the total needed funding. It is
important to keep in touch with the regional EPA offices
and the state agencies dealing with urban runoff
pollution prevention and control to determine the current
status of funding for program implementation. Funding
sources usually available to local jurisdictions fall into
the following categories:
• Local funding mechanisms
• Matching fund programs
• Grant programs
An urban runoff pollution prevention and control
program budget typically includes funds from a
combination of sources. The actual funding sources
utilized depend on many factors, including the following
(PSWQA, 1989):
• The sustainability of the funds.
• The ease with which the funds can be obtained.
• The administrative requirements of the funding
option.
• The correlation between the funding option and the
problem.
• The typical use made of the funding.
The construction of a structural BMP, for example,
typically requires one-time, short-term funding that can
be obtained through a grant or cost share program. The
development of a monitoring or maintenance program,
however, typically requires continuing funding.
Local Funding Mechanisms
Regional, state, and federal storm water and NPS
funding programs are usually intended for small-scale
projects to collect data and demonstrate control
methods. Larger scale programs, therefore, have to be
financed primarily through local mechanisms, including
(U.S. EPA, 1990):
• General funds
• Long-term borrowing
• Pro-rata share fees
• Storm water utilities
• Special assessment districts
General Funds. General funds are raised locally,
usually through property taxes, fees, and fines and can
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be directed to urban runoff pollution prevention and
control. The use of general funds might require
reallocating existing revenues or creating additional
revenue sources. These funds can be used either for
one-time costs or annual operation and maintenance
costs.
Long-Term Borrowing. Local entities can also fund
pollution prevention and control projects through bonds
and other long-term borrowing. Funding through bond
issues is usually used only for one-time expenses,
such as the design and construction of large structural
BMPs.
Pro-Rata Share Fees. Pro-rata share fees can be
used to finance the construction and maintenance of
urban runoff projects. This mechanism requires land
developers to contribute funds to a local entity in
charge of local BMPs. Fees are typically based on a
technical assessment of the development"s potential to
contribute to the urban runoff pollution problem. For
example, a municipality can require developers to pay
a fee based on the amount of impervious surface in the
development. The fees could vary depending on the
development's location (e.g., watershed or proximity to
protected resources). These pro-rata share fees are
often used in currently undeveloped areas where future
development could threaten water resources.
Storm Water Utilities. Many municipalities in urban
areas have begun to set up storm water utilities. Storm
water utilities usually assess all existing residential and
commercial buildings a fee based on their percentage
of impervious area. A survey of 25 storm water utilities
conducted by the Maryland Department of the
Environment in 1987 outlined many of the similarities
and differences among these utility programs (Lindsey,
1988). According to the survey, storm water utilities
had been established in small communities as well as
large urban centers. Most utilities are administered by
local departments of public works, which also have the
responsibility for operation and maintenance of BMPs.
These programs have proved to be good, stable
funding sources.
Special Assessment Districts. Some states have
enacted legislation that allows for the development of
special assessment districts for flood control, lake
management, aquifer protection, drainage, or shellfish
protection. Once a special district is formed, funds for
projects in a district can be raised by levying fees on
landowners in the district. Such programs are viewed
as more equitable forms of financing. Because these
programs require approval of residents in the special
district these funding programs can be difficult to
establish (PSWQA, 1989).
Matching Fund Programs
Matching fund programs (also called cost share
programs) can exist at the regional, state, and federal
level and are typically restricted to financing specific
activities or control measures. In these programs,
entities implementing control programs can obtain
funding for a certain percentage of the cost. Matching
fund programs have been available from the federal
government through the Construction Grants Program,
State Revolving Loan Fund, NPS program (CWA
Section 319), the Clean Lakes Program (CWA Section
314), and the National Estuary Program (CWA
Section 320). Each of these programs is described in
Chapter 2. Matching funds are also available from the
Department of Agriculture through the Soil Conservation
Service and the Agricultural Stabilization and
Conservation Service.
Grant Programs
Regional, state, and federal agencies might also offer
special grants which typically are limited and can
change from year to year. Because of the uncertain
nature of these grants, they are not reliable sources of
funding for long-term programs; however, they can
provide funding for short-term needs. Grants are
available through many of the same federal sources as
for matching funds.
Summary
The final recommended urban runoff pollution
prevention and control plan should be summarized in a
document which can be used by responsible officials
and agencies in plan implementation. An example
of such a plan is provided in the case study on the
Pipers Creek watershed at the end of this chapter.
By developing a thorough and accessible final
implementation document and periodic reports, the plan
will have a greater chance of success. In addition,
valuable information can be compiled for other
communities.
While completion of the urban runoff pollution
prevention and control plan signifies the end of the
planning process described in this handbook, it is
only the first step in the overall program. Plan
implementation will likely be a long-term effort and the
planning is by no means over at this stage. As
implementation and further monitoring occurs, the plan
might need to be updated, refined, and modified. When
this occurs, the planning process described in this
handbook (Figure 3-1) may be re-entered at any point.
For example, a new problem assessment might be
needed, a change in priorities (or problem ranking)
could be necessary, or new BMP options (or deletion of
BMPs previously thought appropriate) might need to be
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considered. The program needs to be reevaluated and
updated constantly throughout implementation.
As a final note, achieving the critical balance between
resources expended on program planning and those
used for program implementation is a challenging task.
The program team must develop a pollution prevention
and control plan using its valuable resources
cost-effectively. Every dollar and manhour not used in
the planning process can be applied to program
implementation. Difficult choices must be made
throughout the planning process to ensure that
technically defensible decisions are made while
still maintaining adequate resources for future
implementation.
Case Study:
Pipers Creek Watershed Action Plan
for the Control of Nonpoint Source Pollution
The Pipers Creek watershed, an urban drainage basin of approximately 3.5 square miles, is located in
northern Seattle, Washington, bordering Puget Sound. To improve the water quality in Puget Sound and
its tributaries, a comprehensive study of the Pipers Creek watershed was conducted during 1989 and
1990 by the city of Seattle and the Washington State Department of Ecology (WA DOE, 1990). This
study led to the development of the Pipers Creek Watershed Action Plan for the Control of Nonpoint
Source Pollution. The plan presents recommended actions, an implementation schedule, regulatory
issues, and remaining needs for the watershed.
The Pipers Creek Action Plan was developed through a 12-step process that closely follows the 7-step
process used in this handbook (see Chapter 3). The steps include:
• Initiate public participation
• Define existing conditions
, • Review regulatory requirements
• Define goals and objectives
• Define and describe the problem
• Identify candidate measures to control NPS pollution
• Employ a practical approach to evaluate candidate pollution control measures
• Develop criteria for evaluating candidate controls
• Examine, evaluate, and screen candidates
• Select most promising source control measures
• Continue assessment of selected source control measures
• Recommend source control measures and an implementation program
In this program, the existing conditions were defined prior to developing and stating program goals. Goals
were reevaluated and redefined at numerous points during the program.
NPS pollution and erosion problems were of highest concern in the Pipers Creek watershed. A watershed
management committee (WMC) was created to develop the action plan, made up of local residents and
representatives of community and environmental organizations, businesses, and local government
agencies. The committee determined that, since NPS pollution is difficult to link precisely to sources, a
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broad range of control measures should be recommended. The following five programs for controllina
NFS pollution were developed:
• Public education: Since some pollution problems were caused by public actions, public education
programs were recommended to inform the general public of actions that result in pollution of surface
waters.
• Regulation: Since some existing regulations could be used to address NFS pollution, regulatory
programs were recommended to increase coordination and enforcement of the existing laws and
regulations designed to prevent water pollution.
• Operation and maintenance: Since existing drainage structure operation and maintenance activities
could be used to reduce NFS pollution, the action plan recommended ways to protect water resources
through improving and coordinating these efforts.
• Public works: Even with full implementation of municipal and regulatory control practices throughout
the watershed, pollution problems would still exist. The action plan therefore, included
recommendations for structural control practices where appropriate, to reduce water quality
degradation.
• Monitoring: The action plan includes recommendations for monitoring management practice
implementation to determine the effectiveness of individual practices as well as a recommendation
for monitoring overall water resources to further characterize the NFS problems.
The recommendations given within these programs are broad in scope and focus primarily on municipal
and regulatory controls (Table 9-2). Controls for specifically identified pollution sources are included in
the public works recommendations and consist of demonstration projects designed to determine the
effectiveness of specific structural controls.
For each of the five programs, WMC has developed detailed recommendations and summarized them
in an action plan that includes conceptual information on recommended BMPs, a schedule of activities,
responsibilities involved in implementation, a description of the monitoring plan, a summary of regulatory
requirements, and identification of funding requirements and sources. The plan also includes a
discussion of pollution prevention and reduction activities that have been implemented already and
additional water resource data that should be obtained.
To increase the effectiveness of the public education program, the WMC and the WA DOE recommended
that some public education activities begin before the action plan is completed. As a result, a number
of actions to inform and educate the watershed community have been initiated with the approval of the
city, including:
• Posting informational signs at key areas in the watershed.
• Stenciling storm drains with a warning against dumping wastes.
• Providing staff assistance to community efforts related to water quality protection.
• Staging a media event and dedicating a billboard promoting the protection of water quality.
• Starting a public education pilot project that provides a half-time watershed educational specialist to
undertake a variety of activities in the watershed.
A detailed plan to implement the recommendations has been developed, including:
• Obtaining written commitments from local and state agencies and citizen's groups responsible for
implementation; these commitments are important given the wide array of agencies and organizations
involved in the program.
• Creating an implementation committee staffed by community representatives and members of
agencies responsible for implementation; this committee is responsible for evaluating program
progress.
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Table 9-2. Pipers Creek Action Plan Recommendations
Public Education
Provide public information during action plan development
Develop a household educational brochure
Hire a watershed specialist to provide education
Develop a park educational display
Develop a watershed educational video
Continue volunteer activities in the watershed
Institute an annual watershed awareness week
Paint signs on storm drains—"Dump No Waste, Drains to
Stream"
Regulatory Controls
Develop a septic system inspection program
Develop a water quality training program for all city
inspectors
Monitor permanent detention systems
Require BMPs at many new construction sites
Install additional pet waste signs
Conduct a study to determine the effectiveness of current
regulations
Install additional dumping enforcement signs
Operation and Maintenance
Develop a program to trace pollution in storm drainage
systems
Locate septic systems serving basements
Expand sanitary sewer system inspections
Inspect the major sanitary system trunk line in the Pipers
Creek watershed
Operation and Maintenance (cont)
Develop a program to determine the correct cleaning
schedule for catch basins
Improve maintenance of open drainage ditches
Provide additional trash receptacles in parks
Expand the existing spill-response program
Public Works
Construct a test grassed swale in the watershed
Conduct a program to test erosion controls
Conduct a test program to increase in-system detention
Reduce erosion from an identified pipe discharge
Reduce erosion from waterside park trails
Install current deflectors to reduce In-stream erosion
Improve the fisheries habitat in park areas
Reduce odor from two sewer systems
Monitoring Program
Create an implementation committee to oversee the action
plan
Conduct routine water quality monitoring
Conduct storm event monitoring in Pipers Creek
Conduct periodic video surveys and a refuse dumping
survey in Pipers Creek
Periodically review watershed land use
Require annual agency status reports
Require annual summary reports of progress in Pipers
Creek
• Developing assessment criteria for the implementation committee to evaluate the program's success;
assessment criteria should include:
— source control recommendations implemented,
- water quality monitoring results,
— opinion surveys,
— recycling participation,
- yard waste collection,
- results of the annual neighborhood cleanup program,
- Earth Day participation,
- return of salmon to Pipers Creek,
- participation in educational events, and
- attention from the local media.
• Developing and implementing a long-term monitoring program, including:
- routine water resource monitoring,
— specific storm event monitoring,
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- visual monitoring, and
- land use monitoring.
• Requiring biannual status reports from each agency responsible for implementation: these reports
should address:
- progress and accomplishments in general,
- problems with implementation,
- actual versus estimated costs,
- suggested modifications to the program, and
— actions for the following year.
Since the recommendations made in this program rely heavily on the data available to the program team,
the initial focus of implementation is on pollution prevention activities, public education, demonstration
projects, and additional data gathering. In this way implementation is not delayed while further water
resource sampling is conducted. Additional sampling and assessment of control measures could lead to
further implementation.
References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
COM. 1993. Camp Dresser & McKee. State of
California storm water best management practice
handbooks. California State Water Quality Control
Board.
Dressing, S.A., J.C. Clausen, and J. Spooner. 1992. A
tracking index for nonpoint source implementation
projects. Proc. National Rural Clean Water Program
Symposium. Orlando, FL.
Lindsey, G. 1988. A survey of stormwater utilities.
Stormwater Management Adminstration, Maryland
Department of the Environment.
Metcalf & Eddy, Inc. 1988. Lower Connecticut River
phase II combined sewer overflow study.
Massachusetts Division of Water Pollution Control.
PSWQA, 1989. Puget Sound Water Quality Authority.
Managing nonpoint pollution: an action plan
handbook for Puget Sound watersheds.
U.S. EPA. 1976. U.S. Environmental Protection Agency.
Methodology for the study of urban storm generated
pollution and control. ERA/600/2-76/145.
U.S. EPA. 1990. U.S. Environmental Protection Agency.
Financing mechanisms for BMPs. Urban Nonpoint
Source/Stormwater Management Fact Sheets. U.S.
EPA Region V. Chicago, IL.
U.S. EPA. 1991. U.S. Environmental Protection Agency.
Evaluating nonpoint source control projects in an
urban watershed. In Seminar Publication: Nonpoint
Source Watershed Workshop. EPA/625/4-91/027
(NTIS PB92-137504).
U.S. EPA. 1992. U.S. Environmental Protection Agency.
Casco Bay storm water management project:
Concord Gully, Frost Gully and Kelsey Brook
watersheds. U.S. EPA Region I. Boston, MA.
WA DOE. 1990. Washington State Department of
Ecology. Pipers Creek watershed action plan for the
control of nonpoint source pollution: final control plan.
Pipers Creek Watershed Management Committee.
Woodward-Clyde Consultants. 1989. Santa Clara
Valley nonpoint source study. Santa Clara Valley
Water District.
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Appendix A
Additional References
When an NTIS number is cited in a reference, that
document is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650
Hydrology References
Andersen, D.G. 1970. Effects of urban development on
floods in northern Virginia. U.S. Geological Survey
Water Supply Paper 2001-C. Washington, DC.
Hammar, T.R. 1972. Stream channel enlargement due
to urbanization. Water Resource Research 8(6).
Klein, R.D. 1979. Urbanization and stream quality
impairment. Water Resources Bull. 15(4).
Leopold, L.B. 1968. Hydrology for urban planning—a
guidebook on the hydrologic effect of urban land use.
U.S. Geological Survey Circular 554. Washington, DC.
Water Resource Sampling References
Plumb, R.H., Jr. 1981. Procedures for handling and
chemical analysis of sediment and water samples.
Technical report no. EPA/CE-81-1. U.S. EPA/U.S.
ACOE Technical Committee on Criteria for Dredged
and Fill Material. Vicksburg, MS: U.S. Army
Waterways Exp. Station.
U.S. EPA. 1973. U.S. Environmental Protection Agency.
Biological field and laboratory methods for measuring
the quality of surface waters and effluents.
EPA/670/4-73/001. U.S. EPA Office of Research and
Development. Cincinnati, OH.
U.S. EPA. 1975. U.S. Environmental Protection Agency.
An assessment of automatic sewer flow samplers.
EPA/600/2-75/065 (NTIS PB-250987).
U.S. EPA. 1975. U.S. Environmental Protection Agency.
Sewer flow measurement: a state-of-the-art assessment
EPA/600/2-75/027 (NTIS PB-250371). Municipal
Environmental Research Laboratory. Cincinnati, OH.
U.S. EPA. 1976. U.S. Environmental Protection Agency.
Design and testing of a prototype automatic sewer
sampling system. EPA/600/2-76/006 (NTIS
PB-252613).
U.S. EPA. 1976. U.S. Environmental Protection Agency.
Methodology for the study of urban storm generated
pollution and control. EPA/600/2-76/145 (NTIS
PB-258743). Office of Research and Development.
Cincinnati, OH.
U.S. EPA. 1982. U.S. Environmental Protection Agency.
Handbook for sampling and sample preservation of
water and wastewater. EPA/600/4-82/029.
U.S. EPA. 1983. U.S. Environmental Protection Agency.
Guidelines for the monitoring of urban runoff quality.
EPA/600/2-83/124 (NTIS PB84-122902).
U.S. EPA. 1986. U.S. Environmental Protection Agency.
Quality criteria for water, 1986. EPA/440/5-86/001.
Washington, DC: U.S. EPA Office of Water,
Regulations and Standards.
U.S. EPA. 1990. U.S. Environmental Protection Agency.
Monitoring lake and reservoir restoration. EPA/440/
4-90/007. Prep, by North American Lake
Management Society. Washington, DC.
U.S. EPA. 1992. U.S. Environmental Protection Agency.
NPDES storm water sampling guidance document.
EPA/833/B-92/001. Office of Water.
WA DOE. 1989. Washington State Department of the
Environment. Guidance for conducting water quality
assessments. Olympia, WA.
Other Nonpoint Source Pollution
References
Metcalf & Eddy, Inc. 1991. Wastewater engineering:
treatment, disposal, and reuse, 3rd ed. New York, NY:
McGraw-Hill.
U.S. EPA. 1992. U.S. Environmental Protection Agency.
Economic analysis of coastal nonpoint source
controls: marinas. U.S. EPA Nonpoint Source Control
Branch: Washington, DC.
U.S. EPA. 1992. U.S. Environmental Protection Agency.
Storm water management for industrial activities:
developing pollution prevention plans and best manage-
ment practices. EPA/832/R-92/006. Office of Water.
Woodward-Clyde Consultants. 1991. Urban BMP cost
and effectiveness. Summary data for 6217(g) guidance:
onsite sanitary disposal systems. December.
169
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Appendix B
Table of Annotated References
Document Title
Author, Date*
BMPs Included
Information Available
Controlling Urban Runoff: A Practical Manual for Planning Schueler, 1987
and Designing Urban BMPs
Protecting Water Quality in Urban Areas MPCA, 1989
Guide to Nonpoint Source Control U.S. EPA, 1987
Water Resource Protection Technology: A Handfoook of ULI, 1981
Measures to Protect Water Resources in Land
Development
Urban Targeting and BMP Selection: An Information and Woodward-Clyde
Guidance Manual for State NPS Program Staff Engineers Consultants, 1990
and Managers
Combined Sewer Overflow Pollution Abatement WPCF, 1989
Urban Storm Water Management and Technology: An U.S. EPA, 1974c
Assessment
Decision Maker's Storm Water Handbook: A Primer U.S. EPA, 1992c
Urban Storm Water Management and Technology: U.S. EPA, 1977
Update and User Guide
Control and Treatment of Combined Sewer Overflows Moffa, 1990
Detention
Infiltration
Vegetative
Filtration
Quality inlets
Housekeeping
Detention
Infiltration
Vegetative
Quality inlets
Housekeeping
Detention
Infiltration
Housekeeping
Detention
Infiltration
Vegetative
Quality inlets
Housekeeping
Detention
Infiltration
Vegetative
Housekeeping
Collection system
Storage
Treatment
Housekeeping
Collection system
Storage
Treatment
Housekeeping
Detention
Infiltration
Vegetative
Filtration
Quality inlets
Source control
Collection system
Storage
Treatment
Source control
Collection system
Storage
Treatment
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Cost
Examples
General descriptions
Effectiveness
Use limitations
Maintenance
Cost
Examples
General descriptions
Effectiveness
Cost
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Cost
General descriptions
Effectiveness
Design
Use limitations
General Descriptions
Design
Effectiveness
Maintenance
Cost
General descriptions
Design
Maintenance •'
Use limitations
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Examples
General descriptions
Design
Maintenance
Use limitations
General descriptions
Design
Maintenance
Use limitations
171
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Document TlUe Author, Date*
Guidance Specifying Management Measures for Source U.S. EPA. 1993b
of Nonpolnt Pollution in Coastal Waters
I r ' I!
The Fforida Development Manual: A Guide to Sound Livingston et al.
Land and Water Management 1988
Storm Water Management Manual for the Puget Sound WA DOE 1991
Basin
BMPs Included
Housekeeping
Infiltration
Vegetative
Filtration
Quality inlets
Housekeeping
Infiltration
Vegetative
Detention
Filtration
Site planning
Housekeeping
Infiltration
Vegetative
Quality inlets
Information Available
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Cost
Examples
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Cost
Examples
General descriptions
Effectiveness
Design
Use limitations
Maintenance
Cost
Examples
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Appendix C
Acronyms and Abbreviations
ARM
ASCS
ATV
BAT
BCT
BMP
BNA
BOD
BOD5
BPJ
CBOD
CCMP
CFR
CMA
CMP
CPM
COD
CSO
CWA
CWO
CZMA
DAF
DEM
DLG
DO
ED
EMC
ENR
EPA
EPT
agricultural runoff model
Agriculture Stabilization and Conservation Service
all-terrain vehicle
best available technology economically achievable
best conventional technology
best management practice
base/neutral and acid extractable compound
biochemical oxygen demand
5-day biochemical oxygen demand
best professional judgment
carbonaceous biochemical oxygen demand
Comprehensive Conservation and Management Plan
Code of Federal Regulations
calcium magnesium acetate
Central Maine Power
critical path method
chemical oxygen demand
combined sewer overflow
Clean Water Act
Comprehensive Watersheds Ordinance
Coastal Zone Management Act
dissolved air floatation
digital elevation model
digital line graph
dissolved oxygen
extended detention
event mean concentration
Engineering News Record
U.S. Environmental Protection Agency
Ephemeropter, Plecoptera, Trichoptera
173
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EXAMS
FEMA
FHWA
GC
GIS
QMS
GWA
HEC
HSPF
IBI
ICI
I/I
LC
LULC
MCL
MCLG
MEDEP
Mlwb
MPN
N/A
NEP
NEPA
NH3
N03
NOAA
NPDES
NPS
NURP
O&M
OSHA
PCB
PCS
PS
PSI
PVC
PW
QAPP
QA/QC
Exposure Analysis Modeling Systems II
Federal Emergency Management Agency
Federal Highway Administration
ground-water conservation
geographic information system
geographic names information system
ground water A (classification)
Hydrologic Engineering Center (U.S. Army Corps of Engineers)
Hydrological Simulation Program—Fortran
index of biotic integrity
invertebrate community index
infiltration and inflow
lake conservation
land use and land cover
maximum contaminant level
maximum contaminant level goal
Maine Department of Environmental Protection
modified index of well being
most probable number
not applicable
National Estuary Program
National Environmental Policy Act
ammonia
nitrate
National Oceanic and Atmospheric Administration
National Pollutant Discharge Elimination System
nonpoint source
Nationwide Urban Runoff Program
operation and maintenance
Occupational Safety and Health Administration
polychlorinated biphenyl
Permit Compliance System
point source
pounds per square inch
polyvinyl chloride
present worth
quality assurance project plan
quality assurance/quality control
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QUAL2E
RC
SCS
SDWA
SLAMM
SOD
SS
SSES
STORM
SWMM
SWTR
IDS
TKN
TN
TOC
TSS
USDA
USGS
UV
VOC
WADOE
WASP4
WMC
WQ
WSE
Enhanced Stream Water Quality Model
resource conservation
Soil Conservation Service
Safe Drinking Water Act
Source Loading and Management Model
sediment oxygen demand
suspended solids
sanitary sewer evaluation survey
Storage, Treatment, Overflow, Runoff Model
Storm Water Management Model
Surface Water Treatment Rule
total dissolved solids
total Kjeldahl nitrogen
total nitrogen
total organic carbon
total suspended solids
U.S. Department of Agriculture
U.S. Geological Survey
ultraviolet
volatile organic compound
Washington Department of Ecology
Water Quality Analysis Simulation Program
watershed management committee
water quality
water surface elevation
175
«,.S. GOVERNMENT PRINTS: OFFICE: 1995-650-006/22045
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