&EPA
United States
Environmental Protection
Agency
Office of Water
(4504F)
EPA842-F-99-0040
January 1999
Evaluating Simple, Cost Effective Solutions for
Reducing Stormwater and Urban Runoff Pollution
Santa Monica Bay Restoration Project
Characteristics
Santa Monica Bay's 414-square mile watershed includes a large
part of the Los Angeles metropolitan area and is home to
approximately three million people.
The bay is vital to the economic health of Los Angeles. Tourism
ranks as the second largest industry in the region. Many of these
visitors flock to the region's primary recreational
resource — Santa Monica Bay. The 22 public
beaches along the bay's 50 miles of shoreline
attract over 45 million visitors each year and
some are world renowned for providing
spectacular surfing opportunities.
In addition, the bay supports a diversity of
habitats and some 5,000 species, including
biologically rich kelp forests the southern-
most run of the endangered steelhead
trout, submarine canyons and an extensive
soft-bottom benthic community.
The Problem
Despite notable environmental
improvements, the bay continues to face
the challenges of health risks to
recreational users and habitat degradation
resulting from urban runoff pollution during both
dry and wet weather.
Los Angeles County and the 21 cities in the watershed are
grappling with implementing Stormwater pollution reduction
technologies, given limited financial resources and the lack of
research on appropriate technologies for the climate and weather
regime found in Southern California.
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PROJECT
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The National Estuary Program
Estuaries and other coastal and marine waters are national
resources that are increasingly threatened by pollution, habitat
loss, coastal development, and resource conflicts. Congress
established the National Estuary Pmgram(NEP) in 2987 to provide a
greater'focus for coastal protection and to demonstrate practical,
innovative approaches for protecting estuaries and their living
resources.
Aspartofthe demonstration role, the NEP offers funding for
member estuaries to design and implement Action Plan
Demonstration Projects that demonstrate innovative approaches to
address priority problem areas, show improvements that can be
achieved on a small scale, and help determine the time and resources
needed to apply similar approaches basin-wide.
The NEP is managed by the U.S. Environmental Protection Agency
(EM). It currently includes 28 estuaries: Aibemarle-PamUco
Sounds, NC; Barataria-Terrebonne Estuarine Complex, LA;
Bamegat Bay, NJ; Buzzards Bay, MA; Casco Bay, ME; Charlotte
Harbor, FL; Columbia River, OR and WA; Corpus Christi Bay, TX;
Delaware Estuary, DE, NJ, and PA; Delaware Inland Bays, DE;
Calves ton Bay, TX; Indian River Lagoon, FL; Long Island Sound,
CT and NY; Maryland Coastal Bays, MD; Massachusetts Bays, MA;
Mobile Bay, AL; Morro Bay, CA; Narragansett Bay, RI; New
Hampshire Estuaries, NH; New York-New Jersey Harbor, NY and
NJ; Peconic Bay, NY; Puget Sound, WA; San Francisco Bay-Delta
Estuary, CA; San Juan Bay, PR; Santa Monica Bay, CA; Sarasota
Bay, FL; Tampa Bay, FL; and TiUamook Bay, OR.
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The Project
The purpose of this project was to demonstrate and evaluate the
effectiveness of catchbasin retrofit devices in reducing pollutant
loads to the bay. The focus was on devices requiring only minor
structural modifications to existing catchbasins, costing no more
than $500 to $1,000 per catchbasin and needing maintenance, on
average, only once per year. Commercially available and easily
constructed devices were evaluated in both wet and dry weather.
Introduction to Santa Monica Bay
Santa Monica Bay is a priceless resource, as vital to its marine
life, birds, and other forms of resident and transient wildlife as it
is to the nine million people who live within an hour's drive of
its shores. However, it has long been adversely affected by the
ills associated with its proximity to the heavily urbanized Los
Angeles basin. While tremendous improvements have been
made, stormwater and urban runoff remain significant
uncontrolled sources of pollution to the bay. Reducing pollution
from these sources is one of the highest priorities in the Bay
Restoration Plan.
Indicative of the problems associated with stormwater and urban
runoff are the findings of the landmark epidemiological study
conducted by the Santa Monica Bay Restoration Project
(SMBRP), linking increased illness rates to swimming near
flowing storm drain outlets and at beaches with high bacterial
indicator densities. Stormwater also carries massive trash loads
to the bay, costing Los Angeles County taxpayers roughly $4
million in beach clean-up costs in 1997. Sediment contaminants
(e.g., metals) are elevated near stormwater discharges and urban
runoff has been found to be toxic to portions of the bay's
benthic community.
Overview of the Project
The Municipal Stormwater/Urban Runoff Pilot Project was
initiated by the SMBRP, which awarded a $100,000 challenge
grant to the City of Santa Monica. With this money, Santa
Monica led the effort to organize a consortium of agencies,
including Los Angeles County, 13 municipalities, one industry
partner and the SMBRP, to collectively undertake a study to
evaluate the feasibility and effectiveness of retrofitting
catchbasins to reduce pollutant loads to the bay. Catchbasins in
Southern California typically are not designed to allow the
solids to fall out, allowing sediments and their associated
contaminants to wash down the drain. The consortium hired
two consulting firms and two researchers from the University of
California at Los Angeles to conduct a series of applied research
studies to meet the project's goal.
Project Objectives
The goal of this project was to evaluate the feasibility and
benefits of using catchbasin retrofit devices as one element in
local stormwater management programs. Three main objectives
(or tasks) were undertaken to achieve this goal:
characterizing local runoff and selecting target pollutants;
evaluating catchbasin retrofits, and
assessing the feasibility and potential environmental benefits
of various inter-city catchbasin retrofit scenarios.
Implementing the Project
Characterize Local Runoff and Select Target Pollutants
Limited sampling was conducted at four sites to confirm the
types and concentrations of pollutants in local urban runoff and
differences between land uses. Target pollutants met the
following criteria:
• present in local receiving waters in concentrations that
threaten beneficial uses,
• discharged via municipal storm drains in significant
quantities, and
• can be removed or reduced by some type of catchbasin
insert.
Based on these criteria and the results of sampling conducted
both prior to and as part of this project, the pollutants selected
for study were total suspended solids, oil and grease, and trash
and debris.
Evaluate Catchbasin Retrofits
Before conducting field and laboratory tests, a set of objectives
for evaluating retrofits was established. The objectives
addressed the cost of the devices and their ability to control the
designated target pollutants, function as operationally practical
components of the municipal stormwater collection system, and
be used in certain municipal applications (i.e., with specific
types of catchbasins and/or for specific types of land use).
Based on previous research and limited modeling, a variety of
catchbasin "inserts" was selected for further evaluation. Inserts
are devices that attach to the catchbasin entrance or mount
inside and thus are relatively easy and inexpensive to install.
Inserts are designed to improve stormwater quality by either
preventing debris and pollutants from entering the basin or by
detaining and treating the water in the basin. Field-testing was
conducted in two areas — one having residential land use and
the other commercial. Laboratory testing included shake tests,
bench-scale column tests, and a full-scale simulation in a
fabricated, aboveground catchbasin. Table 1 summarizes the
results of the field and full-scale laboratory tests for the
candidate devices.
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Table 1: Comparative Pollutant Removal Effectiveness
Retrofit Device
Commercial Device**
Boardover
Debris Basket
Inlet Screen
Sedimentation Baffle
Dry Weather
TSS
none
none
none
none
high
OU&
Grease
mod.
none
none
none
low
Debris
high
high
high
high
high
Wet Weather
TSS
none
NR***
none
NR
mod.
Oil&
Grease
low
NR
none
NR
low
Debris
high
NR
high
NR
mod.
high
*FuU report includes a similar comparison for all evaluation objectives.
Commercial device consisting of an inlet screen panel, debris basket and oil
sorbing columns.
t**"NR" indicates that the device is not recommended.
Assess Inter-city Implementation Scenarios
Several inter-city implementation scenarios were considered,
including city wide implementation, implementation at high
opportunity sites, land-use specific implementation, and
implementation in catchments discharging to sensitive or
targeted receiving waters.
For example, for the land-use specific scenarios, the expected
reduction in the target pollutant load was estimated using data
on the number of catchbasins associated with the particular land
use(s): the predicted pollutant removal efficiency for retrofitted
catchbasins and the estimated pollutant load for the area under
that land use. These calculations are illustrated for free oil and
grease removal in Table 2. Calculations were also made for
removal of trash and debris and total suspended solids under
various scenarios.
Table 2: Estimated Results of Sedimentation Baffle Retrofit
for Free Oil and Grease Removal
Land Die-
Based Retrofit
Alternative
Baywide
Commercial,
Multi-Family
Industrial
Catchbasins
Retrofitted
(approx.
number)
80*02.3201
80%(6.966l
Estimated
Removal for
Sedimentation
Baffle
80%
80%
Total
Watershed
Reduction
64%
43.2%
Reduction in
Actual
Pollutant Load
(in metric tons)
434
293
Based on this pilot project, a decision framework for evaluating
retrofit options was developed to help municipalities select
catchbasin retrofit devices taking into account local conditions
and priorities. The first "decision tree" includes four steps:
1. Determine which pollutants are of concern (e.g., which
impair or threaten beneficial uses),
2. Identify the catchbasins to be controlled (e.g., those
discharging to sensitive water bodies),
3. Decide whether to focus on dry-weather or wet-weather
discharges or both, and
4. Select appropriate devices (e.g., boardovers or screens to
control dry-weather pollutants).
Another decision tree with supporting information helps
planners evaluate different devices based on their technical
feasibility, pollutant removal effectiveness, cost, and operation
and maintenance considerations.
Success Stories
This pilot project is the first to systematically test stormwater
treatment devices under the climate and weather regime found
in Southern California (i.e., arid climate, clearly defined wet
and dry seasons, and high-intensity winter storms).
The project's findings are transferable to coastal Southern
California and other arid regions of the U.S. and, in addition,
the implementation scenarios can be easily updated with new
information.
The project's findings are providing a timely impact on
disbursement of county bond funds for capital improvements
to reduce stormwater pollution — and should prove valuable
to municipalities as they formulate capital project proposals.
Inlet screen panels and boardovers are a very effective and
inexpensive way to prevent nearly all debris from entering
catchbasins during dry weather. In addition, they do not
interfere with street sweeping; in fact, tests showed that the
street sweeper picked up 95% of the accumulated debris in
front of the catchbasin.
Debris baskets are equally effective in both dry and wet
weather; they did not impede flow in field tests, require no
catchbasin modifications and can be easily cleaned out.
Furthermore, they can hold oil sorbents to control oil and
grease. These are probably used most effectively in
commercial areas, which typically generate about three times
the trash as other areas.
Prototype box-shaped debris basket
Lessons Learned
When evaluating stormwater treatment devices, planners should
make sure that devices have been tested based on pollutant
concentrations typically found in urban runoff. Many sorbers,
for example, had been tested based on oil and grease
concentrations in the thousands of milligrams per liter rather
than the more appropriate 10 to 35 mg/1 range typical of urban
runoff.
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Catchbasins should be evaluated in the context of all of the
elements of a watershed-based stonnwater management
program. When considering the use of catchbasin inserts, it is
important to recognize that there are practical limits on which
pollutants can be controlled, what degree of control is possible,
and what is truly "practicable" given that catchbasins must still
perform their function of flood control.
For oil and grease removal, the most cost-effective land use-
based approach is to target commercial, multi-family and
industrial areas. Reducing the number of retrofits by 44%, but
focusing on the land uses that generate more oil and grease, still
affords a pollutant load reduction of 67% of the baywide
scenario (see Table 2).
The volume of most Southern California catchbasins is large
enough to allow significant capture of total suspended solids
and fine paniculate-related pollutants. The most cost-effective
scenario for controlling total suspended solids is to focus on
catchbasins where pollutant removal would be highest (e.g.,
those with larger volume to tributary area and imperviousness
ratios).
For Further Information
Previous Publications in the Demonstration Projects Series
Report Title
Biological Nutrients Removal Project
Buttermilk Bay Colifomi Control Project
Georgetown Storrawater Management Project
Texas Coastal Preserves Project
Shell Creek Stonnwater Diversion Project
City Island Habitat Restoration Project
Buzzards Bay "Sep Track" Initiative
New Options for Dredging in Barataria-Terrebonne
Coquina Bay Walk at Leffis Key
"Pilot Project Goes Airborne"
The National Estuary Program: A Ten- Year Perspective
Rock Barbs In Oregon's Tillamook Bay Watershed
The Weeks Bay Shoreline & Habitat Restoration Project
Evaluation of Shrimp Bycatch Reduction Devices in Texas Coastal Bend Waters
National Estuary Program
Long Island Sound, CT/NY
Buzzards Bay, MA
Delaware Inland Bays, DE
Galvcston Bays, TX
Puget Sound. WA
Sarasota Bay, PL
Buzzards Bay. MA
Baralaria-Terrebonne Basin, LA
Sarasota Bay, FL
Narraganscti Bay, RI
General NEP Discussion
Tillamook Bay, Oregon
Mobile Bay, AL
Corpus Christi, TX
Date
1995
1995
1995
1995
1995
1995
1997
1997
1997
1997
1998
1998
1998
1998
Publication #
EPA842-F-95-001A
EPA842-F-95-001B
EPA842-F-95-001C
EPA842-F-95-001D
EPA842-F-95-OOIE
EPA842-F-95-001F
EPA842-F-97-002G
EPA842-F-97-002H
EPA842-F-97-002I
EPA842-F-97-002J
EPA842-F-98-003K
EPA842-F-98-003L
EPA842-F-98-003M
EPA842-F-99-003N
For Copies of any of these publications contact:
National Clearinghouse for Environmental Publications Telephone: (513)489-8190 Facsimile: (513)489-8695
&EPA
United States
Environmental Protection Agency
(4504F)
Washington, DC 20460
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