United States Environmental
Protection Agency and the
EPA Region III states of
Pennsylvania, Maryland,
Delaware, District of Columbia,
Virginia and West Virginia
Evaluating the Effectiveness
of Municipal Stormwater Programs
EPA833-F-07-010
January 2008
(A
t to
NPDES Stormwater Management Programs
EPA stormwater regulations require National Pollutant Discharge
Elimination Program (NPDES) permits for stormwater discharges
from many municipal separate storm sewer systems (MS4s).
Phase I of the stormwater permit program generally addresses
municipalities with greater than 100,000 in population, while
Phase II addresses smaller jurisdictions within urban areas.
Additional information on EPA's stormwater program is available
at www.epa.gov/npdes/stormwater.
Stormwater Phase II programs address the following program
components:
» Public education and outreach
» Public involvement
» Illicit discharge detection and elimination
» Construction Site Runoff Control
» Post-Construction Runoff Control
» Pollution Prevention/Good Housekeeping for Municipal
Operations
In addition to the programs above, Stormwater Phase I programs
also must address stormwater runoff from industrial facilities.
Operators of regulated MS4s are required to develop a
stormwater management plan (SWMP) that includes measurable
goals and to implement needed stormwater management
controls (BMPs). The process of developing a plan, implementing
the plan, and evaluating the plan is a dynamic, iterative process
that helps move communities toward achievement of their goals
(Figure 1).
40 CFR 122.26(d)(2)(v) and 122.34(g) requires MS4s to assess
controls and the effectiveness of their stormwater programs.
Municipal stormwater programs are also required to reduce the
discharge of pollutants to the "maximum extent practicable"
and satisfy the water quality requirements of the Clean Water
Act. In addition, a number of government and scientific reports
have found that better water quality data is needed if MS4s are
to evaluate the effectiveness of their program in meeting water
quality goals (NRC, 2004; Schwarzenback, et. al, 2006; Vaux,
2005).
This document discusses three approaches to evaluation of
municipal SWMP effectiveness:
» Assessing program operations;
» Evaluating social indicators; and
» Monitoring water quality.
Other guidance is available to assist managers in evaluating
overall implementation of the SWMP to the maximum extent
practicable, e.g., EPA's MS4 Program Evaluation Guidance
(www.epa.gov/npdes/pubs/ms4guide_withappendixa.pdf).
Purposes of Program Evaluation
» Meet regulatory requirements. EPA stormwater regulations
require that the effectiveness of the SWMP be evaluated,
including assessment of SWMP implementation, evaluation of
BMP effectiveness, and the extent to which improvements in
stormwater outfall discharge quality have occurred.
» Document progress toward water quality goals. Evaluation of
SWMP effectiveness is essential to measure progress toward
meeting benchmark conditions, complying with water quality
standards, or restoring beneficial uses.
» Justify commitment of resources. Knowledge of program
effectiveness can help justify SWMP expenditures to decision-
makers and to the public, and help improve cost-effective
implementation and management of the SWMP.
» Provide feedback to the management program. Stormwater
management is an iterative process and knowledge of
program effectiveness is essential for the permit renewal
process and for mid-course corrections to improve the
program.
» Assess reductions in pollutants of concern. If a waterbody is
impaired, it may be helpful to assess the effectiveness of the
SWMP in reducing the pollutants of concern.
Figure 1. The iterative process of stormwater management
(Develop, implement, evaluate, repeat).
-------
EPA833-F-07-010
Evaluating the Effectiveness of Municipal Stormwater Programs
M
Setting Goals for SWM Ps
Stormwater management plans must be guided by specific
measurable water quality-based goals, but also typically include,
programmatic, BMP-implementation, and social goals. NPDES
permit conditions often serve as minimum goals for a SWMP,
but an MS4 may have other goals for restoration or protection
of water quality that go beyond minimum permit conditions
and reflect local understanding of the storm drain system and
receiving water conditions. Guidance on setting measurable
goals for SWM Ps can be found in EPA's Measurable Goals
Guidance for Phase II Small MS4s (www.epa.gov/npdes/pubs/
measurablegoals.pdf).
Programmatic goals might address education and outreach to a
range of audiences, establishment of partnerships with business
owners, or adoption of ordinances. BMP implementation goals
may call for some number of practices to be installed in key
locations according to a certain schedule. Goals for public
involvement could include targets for number of participants
in clean-up or tree-planting activities, number and quality of
responses to attitude surveys, or changes in the use of lawn
fertilizer.
The ultimate goal of any NPDES Stormwater management
program is to reduce pollutant discharges to the maximum extent
practical, prohibit illicit discharges to the MS4, and protect water
quality. Water quality goals may pertain to pollution prevention
(reduction of potential pollutants at the source), improvements
in Stormwater outfall discharge quality, reduction of pollutant
loads to receiving waters (e.g., a TMDL), restoration of aquatic
resources (e.g., stream channel stabilization, fishery restoration),
compliance with water quality standards, or restoration of
beneficial uses. Intermediate benchmarks that indicate progress
toward meeting water quality standards are important elements
of successful long-term SWMPs.
"to
Evaluation of the effectiveness of a SWMP must relate directly
to its goals. Two central questions are: Are we meeting the
municipal SWMP goals? and Are we meeting NPDES Stormwater
regulatory requirements? If a goal is to keep a swimming
beach open, it is often necessary to determine the extent
to which water quality criteria for bacteria are being met. If
a goal is to reduce nutrient loads by 40% from a watershed,
it is then necessary to measure nutrient loads and compare
measured loads against the goal. Meeting your water quality
goals is the ultimate sign of program success, however, meeting
programmatic or social goals can also be indicators of a
successful program. Information on how these goals are met will
serve as critical feedback in the iterative process of Stormwater
management.
M
Stormwater program evaluation must be more than an exercise
in collecting and tabulating data; evaluation data must be
analyzed, interpreted, and reported so that results can be
applied to such purposes as documenting effectiveness of
BMPs, reporting information to government or the public, and
planning future management activities.
Stormwater programs address multiple objectives and program
evaluation can focus on a variety of desired outcomes that
parallel these objectives. Approaches to the evaluation of
Stormwater program effectiveness may therefore fall on a
continuum from basic verification of compliance with regulatory
requirements to assessing changes in knowledge and behavior
to detecting changes in receiving water quality (Figure 2).
The NPDES Stormwater evaluation program in Baltimore
County, Maryland (www.baltimorecountymd.gov/Agencies/
environment/watersheds/epnpdesmain.html) is a good example
of effective evaluation of an MS4 program.
Level 6-
Changes in
Receiving Water
Quality
Level 5-
Changes in Urban Runoff
& Discharge Quality
Level 4 - Load Reductions
Level 3 - Behavioral Change & BMP Implementation
Level 2 - Changes in Attitudes, Knowledge, & Awareness
Level 1 - Compliance with Activity-Based Permit Requirements
Figure 2. Approaches to evaluation of Stormwater program
effectiveness. (Source: CASQA, 2007)
In this document, we consider the range of evaluation
approaches in three groups: program operations, social
indicators, and water quality. Every evaluation approach must
contain appropriate water quality measures to be meaningful.
Assess program operations
Assessment of Stormwater program operations and activities
verifies basic compliance with permit requirements and, more
importantly, documents that tangible efforts have been made
to reduce the impacts of urban Stormwater. This approach to
program evaluation can be applied to all of the components of a
SWMP.
-------
EPA833-F-07-010
Evaluating the Effectiveness of Municipal Stormwater Programs
Track structural BMP implementation. Tracking the type
and number of structural BMPs installed provides managers
with direct feedback on how implementation is progressing
and whether goals set forth in the permit are being achieved.
Data on BMP specifications, location, date of completion,
compliance with permit conditions, and ongoing operation
and maintenance may be important to record. See USEPA
Techniques for Tracking, Evaluating, and Reporting the
Implementation of Nonpoint Source Control Measures:
Urban (www.epa.gov/owow/nps/urban.pdf) for more
information on the topic of tracking BMPs implemented in
yourjurisdiction.
Document management activities. Documenting
management activities and pollutant source reduction efforts
can be as important as tracking structural BMPs. How much
material has been collected through street-sweeping and
parking lot maintenance? How many site inspections were
conducted and what were the results? How many and what
type of illicit discharges were identified and eliminated? How
many trainings and outreach activities were conducted, and
how many people were reached? Baltimore City, Maryland,
focuses limited stormwater management resources in a small
highly urbanized watershed to demonstrate how making
communities more livable can improve water quality. An
important part of this effort is to document management
activities so that both managers and residents can easily
follow progress.
Evaluate social indicators
Social indicators—changes in knowledge, attitudes, and behavior
of people—are important for two reasons. First, some SWMPs
may have goals for increasing knowledge and awareness and
changing attitudes among groups such as residents, business
owners, and municipal employees. Second, social indicators—
especially behavior changes—are important intermediate
benchmarks in a successful SWMP when many years are needed
to measure a water quality response. For more information,
see Developing a Social Component for the NPS Evaluation
Framework (www.uwex.edu/ces/regionalwaterquality/
Flagships/Indicators.htm). This approach to program
evaluation is typically applied to the public education and public
participation components of a SWMP.
Gauge the effects of public education efforts. Changes
in awareness, knowledge, and attitudes can be measured
effectively using statistically valid surveys or questionnaires;
for example see Stormwater Knowledge, Attitude and
Behaviors: A 2005 Survey of North Carolina Residents
(www.ncstormwater.org/pdfs/stormwater_survey_
12506.pdf). Other approaches include monitoring attendance
at public meetings, tracking requests for information, and
counting hits on web sites. Keep in mind that simply reporting
the number of meetings held or the number of brochures
printed is not an effective method to document changes in
stormwater knowledge.
Assess behavior changes. Measurement of change in
pollution-generating behavior in a watershed can be an
important indicator of progress toward achieving SWMP goals.
Examples include: changes in lawn fertilizer sales in response
to a publicity campaign, pounds of hazardous waste turned
in at collection events, participation in streambank clean-up
events, and sign-ups for environmental action pledges.
Mo^i'tor
Water quality monitoring is the most direct—and usually the
best—approach to evaluating the effectiveness of a SWMP.
Program evaluation through water quality monitoring can apply
to several of the SWMP components, including illicit discharge
detection, construction site runoff control and post-construction
runoff control. The collection of water quality data (along with
BMP performance data) would be especially useful for discharges
to an impaired water body with an approved TMDL. (For more
information about the TMDL program, visitwww.epa.gov/owow/
tmdl). Detailed guidance on design and operation of monitoring
is available elsewhere, e.g., USDA-NRCS National Handbook
of Water Quality Monitoring (ftp://ftp.wcc.nrcs.usda.gov/
downloads/wqam/wqml.pdf) and EPA Monitoring Guidance
for Determining the Effectiveness of Nonpoint Source Controls
(Sept. 1997, EPA 841-B-96-004).
Water quality monitoring approaches range from qualitative
observations to highly quantitative measurements, covering
areas as small as individual BMPs to large receiving waters such
as lakes or estuaries. A good monitoring program for evaluation
of SWMP effectiveness will probably contain several elements
at various levels of detail and scale. Before embarking on new
monitoring, however, it is important to collect and evaluate
historic and current data from existing monitoring activities.
Data from state 305(b) assessments, 303(d) lists, and published
TMDLs, ongoing state and federal agency monitoring programs,
water supply intake testing, and watershed volunteer groups, for
example, can be useful both in designing a monitoring program
and in supplementing program results.
Monitoring can focus on biological (e.g., E. coli, fish), physical
(e.g., flow, suspended sediment, streambank stability), or
chemical (e.g., phosphorus, trace metals) dimensions of the
water resource. Measured water quality variables should be
directly linked to both the pollutant sources and the BMPs being
implemented. In general, a monitoring program should focus
on selecting a few good water quality variables to measure
well, rather than trying to track a long list of indicators. For
example, for a swimming beach impaired by bacteria, it would
be appropriate to monitor the swimming area, nearby storm
drain outfalls, and tributary flows for E. coli. If stream channel
blow-outs are an issue and BMPs addressing excessive flows
are implemented, monitoring of streamflow and channel cross-
section conditions would be a good choice. For algal blooms,
monitoring of nutrient concentrations and loads to the receiving
water might be appropriate.
Water quality monitoring must take hydrologic variation into
account. Most stormwater pollution processes are driven by
rainfall that varies from year to year. If several dry years follow
-------
EPA833-F-07-010
Evaluating the Effectiveness of Municipal Stormwater Programs
implementation of a SWMP, the program may appear to be highly
effective in reducing pollutant loads simply because runoff is
unusually low. Conversely, several years of wet weather could
result in higher pollutant loads simply because of increased
runoff volume despite BMP implementation. Consequently, it
is important to monitor precipitation and streamflowto help
interpret results from all but a few highly qualitative monitoring
approaches.
MS4s can take a variety of monitoring approaches to evaluate
their SWMP effectiveness. Several common approaches that
can be implemented for physical, chemical, and biological
dimensions of water quality are listed at the end of this
document.
The
"to
Management of stormwater programs is an iterative process,
beginning with planning, progressing through implementation
and program evaluation, and then returning to the beginning
of the cycle with feedback to further program planning.
Effectiveness evaluation assesses how well implementation is
working and estimates benefits derived from the program for the
primary purpose of assessing progress toward program goals
and compliance with regulatory requirements. Results can also
be used to make practical changes in management strategies.
Effective program feedback will enable local governments to
guide decisions on shifting priorities to achieve goals more
cost-effectively, including modification of activities that need
improvement, expansion of effective activities, and cessation
of efforts that are no longer productive. Results of SWMP
evaluation should be presented to decision-makers in a clear
manner that addresses the questions formulated when the
evaluation plan was designed.
Reporting
Annual reports are a good place to summarize evaluation results
and to take stock of what is working and what is not. Data
gathered throughout the year should be used to answer critical
questions such as:
» What is the current status in meeting stormwater goals and
NPDES regulatory requirements?
» What are the estimated load reductions and other benefits of
BMP implementation?
» What are the costs associated with program implementation?
» How do the costs of program implementation relate to water
quality changes?
» What stormwater program changes are necessary to meet the
stated goals?
The Baltimore City, Maryland MS4 2005 NPDES permit, for
example, requires the permittee to provide an annual narrative
summary describing the results and analyses of program data,
including monitoring data accumulated throughout the reporting
year. Identification of water quality improvements or degradation
is a key part of this requirement.
Fourth-year reports are a good opportunity to use data gathered
under the entire permit period to guide future management
direction. Continuation of a NPDES permit typically requires
the permittee to submit with its permit renewal application a
summary of its SWMP describing how water quality goals are
being achieved. Information in the application would include
measured pollutant load reductions resulting from SWMP
implementation and achievement of other benchmarks or water
quality standards. Analysis of evaluation data is also used to
justify or support changes in the permit and SWMP.
Feedback to the stormwater management program
NPDES regulations require assessment and revision of the
stormwater management program in order to continue, to the
maximum extent practicable, to not cause or contribute to
water quality standards exceedances. As part of the iterative
management process, stormwater program activities should be
adjusted based on the results of an effectiveness evaluation.
If a management goal has been achieved, effort in this area
might be reduced to a maintenance level and resources
reallocated to another pollutant or goal. If a goal has not been
achieved, or satisfactory progress has not been made, additional
resources can be applied and new strategies implemented. Such
adjustments provide the direction for a municipality's permit
renewal and will ensure progress toward program goals.
Effectiveness evaluation can also apply to ongoing stormwater
programs through the process of adaptive management. Through
this, evaluation results on program operations, social or water
quality can provide rapid feedback to guide management
activities. For example, an MS4 might establish dry weather
action levels—or targets—for water quality constituents such as
turbidity, phosphorus, and trace metals in tributaries draining to
receiving water. Exceedance of an action level in samples taken
from a tributary during dry weather would trigger an immediate
investigation upstream to find and eliminate illicit connections
and illegal discharges. Dry weather action levels would be
reviewed and updated annually based on monitoring data and
progress toward meeting SWMP goals.
In another example (Figure 3), coastal beaches and storm drains
discharging near them are monitored for fecal bacteria. When
compared against storm drain action levels for bacteria (sampled
at the storm drain) and bacteria water quality criteria for body
contact recreation (sampled in the open coastal receiving water),
results of the paired samples guide management decisions on
actions needed to protect the beach and follow up on sources of
high bacteria counts.
Multi-faceted stormwater management programs can be
evaluated as well. Baltimore City's NPDES stormwater permit
requires it to restore a watershed or combination of watersheds
containing 10% of the City's total impervious area during each
five-year permit. The City conducts comprehensive watershed
assessments and goals for restoration are developed based on
-------
EPA833-F-07-010
Evaluating the Effectiveness of Municipal Stormwater Programs
Beach
Meets bacteria Fails to meet
criteria bacteria criteria
Storm drain discharge
Below
bacteria
action level
Above
bacteria
action level
No action required
Storm drain discharge
not causing beach
impairment; investigate
storm drain sources
Storm drain discharge
not causing beach
impairment; continue to
monitor and investigate
other sources
Storm drain discharge
causing beach
impairment; investigate
storm drain sources ASAP
Figure 3. Decision table for storm drain and beach bacteria
levels.
severity of water quality problems, input form local watershed
associations, the possibility for inter-jurisdictional cooperation,
and the availability of restoration opportunities. One restoration
priority is Watershed 263 (www.cwp.org/RR_Photos/
Baltimore_City_profile_sheet.pdf) where Baltimore City plans to
restore a degraded stream system and simultaneously address
other social and economic problems associated with older urban
environments. The goals in this watershed include; replacing
school yard asphalt with green infrastructure to filter stormwater;
replacement of sidewalk sections with trees to remove nutrients
and reduce the "heat island" effect; conversion of vacant
abandoned lots into gardens for local residents to use; reduce
the buildup of trash and litter through increased municipal street
sweeping; and installing innovative ultra-urban BMPs wherever
possible. A catch basin downstream of all of these activities
will be monitored for water quality and compared to a similar
watershed in the City with no controls. Since the installation
of BMPs will be progressive, monitoring data will show the
effectiveness of differing management strategies. Information
will be fed back into future management plans for this watershed
and others across the City to ensure that stormwater is being
controlled to the maximum extent practicable.
In summary, a municipal stormwater management program
needs to set clear goals and identify appropriate monitoring
methods to evaluate those goals in order to assess the
effectiveness of the stormwater program in protecting water
quality.
Monitoring/Evaluation Guidance or References
California Stormwater Quality Association (CASQA), 2007, Municipal
Stormwater Program Effectiveness Assessment Guidance. Available at
www.casqa.org
Southern California Coastal Water Research Project, Model Monitoring
Program for Municipal Separate Storm Sewer Systems in Southern
California. ftp://ftp.sccwrp.Org/pub/download/PDFs/419_smc_
mm.pdf
EPA, 1992, NPDES Stormwater Sampling Guidance Document,
EPA 833-B-92-001. www.epa.gov/npdes/pubs/owm0093.pdf
Center for Watershed Protection, Smart Watershed Benchmarking Tool.
Available at www.cwp.org
Chesapeake Bay Program, BMP Efficiencies and Definitions.
www.chesapeakebay.net/pubs/subcommittee/nsc/uswg/
BMP_Pollutant_Removal_Efficiencies.pdf
International Stormwater BMP Database, Development of Performance
Measures: Determining Urban Stormwater Best Management Practice
Removal Efficiencies (www.bmpdatabase.org/docs/task3_l.pdf) and
Urban Stormwater BMP Performance Monitoring: A. Guidance Manual
for Meeting the National Stormwater BMP Database Requirements
(www.bmpdatabase.org/docs/Urban%20Stormwater%20BMP%20
Performance%20Monitoring.pdf)
Stormwater Manager's Resource Center, Environmental Indicator Profile
Sheet: BMP Performance Monitoring, www.stormwatercenter.net/
monitoring%20and%20assessment/ind%20profiles/lndPros25.pdf
State/Municipal examples of monitoring/evaluation
programs
Baltimore County, Watershed Management and Monitoring.
www.baltimorecountymd.gov/Agencies/environment/watersheds/
ep_watershed_monitoring.html
City of Hialeah, FL Stormwater Utility Monitoring Program.
http://hialeahfl.gov/dept/streets/stormwater/plans/monitoring
Maryland Watershed Restoration Action Strategy.
www.dnr.state.md.us/watersheds/surf/proj/wras.html
Ventura, California, MS4 Permit
www.swrcb.ca.gov/rwqcb4/html/programs/stormwater/
venturaMs4.html
National Research Council (NRC), 2004. Confronting the Nation's
Water Problems: The Role of Research, National Academies Press,
Washington, D.C.
Schwarzenbach, R.P., B. I. Escher, K. Fenner, T. B. Hofstetter, C. A. Johnson,
U. von Gunten, B. Wehrli. 2006."The Challenge of Micropollutants in
Aquatic Systems" Science, volume 313, p!072.
Vaux, H. 2005 "Water Resources Research in the 21st Century", Journal of
Contemporary Water Research and Education, Issue 131, pp 2-12.
U.S. EPA-Paula Estornell
estornell.paula@epa.gov
Maryland—Ray Bahr
rbahr@mde.state.md.us
Virginia—Douglas Fritz
Doug.Fritz@dcr.virginia.gov
NOTE: This document is not law or regulation; it provides
recommendations and explanations that MS4s may consider in
determining how to comply with requirements of the CWA and
NPDES permit requirements.
-------
EPA833-F-07-010
Evaluating the Effectiveness of Municipal Stormwater Programs
Useful Water Quality Monitoring Approaches for Evaluation of SWMPs
Visual observations. Some water quality conditions can be assessed by
visual (qualitative) observations of controls, outfalls or receiving waters.
Searching for and correcting illicit discharges through observation of
oil and grease sheens, floatables, or odors at outfalls is one example.
Progress in streambank stabilization and channel restoration might be
monitored by regular photography of critical locations. In general, qualitative
observations should be supplemented by quantitative measurements
where possible, such as with dry weather sampling at outfalls or regular
surveys of representative stream cross-sections. The City of Albuquerque
MS4 Floatable & Gross Pollutant Study (www.cabq.gov/flood/pdf/
FINALREPORT-OCTOBER2005.pdf) is an example of a systematic approach
to qualitative observations of water quality conditions. Examples of survey
techniques for streambank assessment can be found in the Maryland
Stream Corridor Assessment Survey (www.dnr.maryland.gov/streams/
pubs/surveyprotocols2.pdf) and the USACE/USEPA Review of protocols for
stream assessment (www.mitigationactionplan.gov/
Physical%20Stream%20Assessment%20Sept%2004%20Final.pdf).
BMP performance monitoring. Monitoring of individual BMP performance
provides a direct measure of pollutant reduction efficiency of these key
components of a SWMP. Conceptually, BMP input/output monitoring is
simple—measure pollutant concentrations or loads entering and leaving
a wet pond for example, and compute the difference. In practice, BMP
monitoring is more complex, requiring careful collection of data concerning
storm and runoff characteristics and information on BMP attributes, as
well as water quality information. There are several sources of information
on BMP performance and on protocols for collecting, storing, analyzing,
and reporting BMP monitoring data, including the National Stormwater
BMP Database (www.bmpdatabase.org) and the USEPA and ASCE Urban
Stormwater BMP Performance Monitoring Manual. Some examples of
individual BMP monitoring studies can be found at the Villanova Urban
Stormwater Partnership (www3.villanova.edu/VUSP/index.html).
Probability monitoring. Monitoring sites can be selected across a
broad geographic area according to some statistical design to broadly
characterize water quality conditions in a watershed or to identify possible
contamination hotspots. Site selection could be random to achieve
wide spatial coverage or stratified to focus monitoring on particular
environment types or represent specific target populations. Data from
a statistical sample of stream riffle sites across a watershed could be
used to assess the overall condition of watershed macroinvertebrate
communities. A monitoring program addressing sediment toxicity in a bay
might geographically direct sampling to ensure that sediments in different
depositional environments or with different physical characteristics are
sampled, or that samples are collected within the areas affected by
discharges from major tributaries. Results of probability monitoring can
be used to guide SWMP implementation efforts and to assess long-term
trends in response to SWMP implementation. An example of a probability
design applied to evaluating sediment toxicity is found in the NOAA
report Magnitude and Extent of Contaminated Sediment and Toxicity in
Chesapeake Bay (ccma.nos.noaa.gov/publications/NCCOSTM47.pdf).
Short-term extensive network monitoring. Short-term grab-sampling at
the outlets of numerous small watersheds or other drainages within a
large MS4can identify impaired waters and rank areas for implementation
priority. Data collected simultaneously across the MS4 can help
characterize the geographical distribution of pollutant sources. The City of
Los Angeles monitors a network of shoreline stations in Santa Monica Bay
for bacteria to identify Stormwater impacts on recreational uses of the bay.
This approach can apply not only to streams draining small watersheds but
also to storm drains during both wet-weather and dry-weather conditions.
If continued over several years, this kind of monitoring can be a good
opportunity for volunteer groups to participate in the SWMP evaluation
process. Data collected by volunteers could be reported separately or
incorporated within "official" data sets used for regulatory purposes
depending upon the methods used and level of training provided to
volunteers.
Site-specific monitoring. High-value resources such as popular swimming
beaches, important shellfish beds, or high-priority habitats could require
specific monitoring to regularly assess the status of use support. Similarly,
known high-priority pollutant sources or hotspots of impairment like
contaminated aquatic sediments, an eroding stream channel threatening
property, or a stream reach with a degraded fish population could be
monitored to assess progress in restoration. Depending on the situation,
such monitoring can be done in the critical area itself to assess its
condition or upstream and downstream of the area to evaluate changes in
pollutant stressors. Fairfax County's MS4 program conducts an Industrial
and High-Risk Runoff monitoring program to identify and investigate
industrial and other high-risk sites to determine if they are contributing
substantial pollutant loadings to the MS4. The San Diego Bay MS4
permittees operate a Toxic Hot Spots Monitoring Program to locate and
track areas of aquatic sediment contamination related to discharges from
MS4s around the Bay.
Long-term fixed stations. Permanent monitoring stations at major
discharges from an MS4 or on a receiving water above and below an MS4
can be used to measure changes in pollutant loads discharged from the
MS4. Such stations are usually located where it is easy to measure flow
and collect representative samples. Accurate load measurement requires
consideration of many factors including patterns of hydrologic variation,
seasonal patterns of pollutant concentrations, and desired statistical
power; it is advisable to consult a monitoring expert before setting up
a sample program to monitor pollutant loads. Flow, concentration, and
load data from long-term fixed stations can be used for many purposes,
including assessing compliance with water quality standards, collection
of representative data from drainage areas that are undergoing similar
activities and where the discharges are expected to be of similar quality
as required in some MS4s under Phase I rules, documenting water quality
trends, and marking progress toward meeting pollutant load goals, e.g., for
a TMDL. The Los Angeles County Stormwater monitoring program operates
a system of mass emissions stations (www.ladpw.com/WMD/npdes/
Int_report/Section_l.pdf) to update estimated pollutant loads to the ocean
and to document long-term trends in pollutant concentrations. The San
Diego region urban runoff monitoring program maintains similar long-term
mass loading stations (www.projectcleanwater.org/pdf/
science_mon/2003-2004_monitoring_summary.pdf) that regular
assessment of the biological communities as well as chemical pollutant
loads in major drainages.
Receiving water monitoring. Protection of a water body receiving
discharges from an MS4 is often the ultimate goal of Stormwater
management. However, an MS4 may not be the only Stormwater
discharge into a water body, and achievement of the MS4's discharge
quality goals may not eliminate the impairment in the receiving water.
It may nevertheless be important to monitor water quality in the river,
lake, estuary, or bay that receives its discharge, especially if localized
impacts can be identified. Evaluation of the effectiveness of a SWMP on
maintaining recreational benefits, for example, might involve monitoring
both storm drains and swimming beaches for E. coli. If a goal of a SWMP
is to reduce the impacts of toxic materials delivered in Stormwater, a
program monitoring a combination of water and sediment chemistry,
sediment toxicity, and benthic communities in the receiving water might be
appropriate.
------- |