An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Multiple Benefits in a County's Stormwater Control Program

Program Overview

When the federal government issued new National Pollutant Discharge Elimination System stormwater permitting rules, the Montgomery County, Maryland, Department of Environmental Protection (DEP) considered several ways of responding. They first looked at the typical practice of chemically based runoff monitoring and decided this approach would not be useful in evaluating the multiple and cumulative causes of impairment of the county's surface waters. Most impairment resulted from the alteration of stream flows, which caused sediment, stability, thermal, and other problems. In addition, many county streams are small headwater streams or small second- or third-order streams, and very few receive direct point source discharges from treated wastewater. Chemical and physical monitoring data indicated that most of the streams regularly met state water quality standards (e.g., dissolved oxygen, pH, and temperature), yet the quality of the biological resources supported in these streams varied greatly. To assess the causes of this variability and identify effective management approaches, the DEP felt that selecting and monitoring cost-effective indicators of the cumulative impacts occurring in county streams was critical. A biological monitoring program was selected as the approach that would best meet this need.

Uses of Bioassessment in Montgomery County

  • To identify baseline stream conditions
  • As a screening tool to evaluate cumulative watershed impacts
  • To isolate specific causes of biological impairment
  • To assess effectiveness of innovative BMP and development designs for the county's Special Protection Area Program
  • To establish current stream conditions for the Countywide Stream Protection Strategy

The NPDES permit that was negotiated between the county and the State of Maryland enables integration of biological and stream habitat monitoring results into a comprehensive, countywide, watershed-based approach to stream protection and restoration. This program has been cost-effective and has had the added benefit of invigorating public outreach and education programs, which in turn have fostered public support for the county's efforts to protect and improve stream quality.

The County DEP monitors fish and benthic macroinvertebrates using protocols based on EPA's Rapid Bioassessment Protocols. The study design, field methods, and definition of interim reference conditions (Van Ness et al., 1997) were developed by consensus through the county's biological monitoring workgroup. An interim index of biological integrity (IBI) for fish and an IBI for benthic macroinvertebrates were developed as primary assessment tools. These IBIs are based on data from over 40 monitoring stations in the county's least impaired streams. Using these IBIs as "yardsticks," the biological conditions in baseline watersheds are ranked as being in excellent, good, fair, or poor condition. Habitat conditions are assessed using EPA's Rapid Habitat Assessment Protocol. The relationship between the biological condition and the habitat condition is compared to identify possible causes of stream impairment. If the biological resource and stream habitat quality both show impairment, emphasis is placed on improving stormwater controls in the watershed and on restoring degraded habitat, where such restoration measures are feasible and cost effective. If the habitat is good or excellent, but the biological resources are impaired, flow-related events (storm flow, suspended sediment, elevated temperatures) or illicit discharges are investigated as possible causes. On the other hand, if the biological conditions are better than expected for the habitat, sources of nutrient enrichment are investigated.

The approach taken by the county's biological stream monitoring program is readily understood by residents, elected officials, and staff responsible for maintaining and improving the water resources within the county. In 1997, the DEP was asked to develop a countywide stream protection strategy to provide direction and priorities for watershed restoration. Using biological monitoring data, and a monitoring partnership with local and state agencies, Montgomery County has been able to evaluate resource conditions in 275 subwatersheds within its 507 square mile jurisdiction. Coupled with GIS database information and other analytical tools, the county has been able to efficiently evaluate stream conditions and quantify important information from the contributing watersheds (such as existing piped drainage, existing and projected changes to impervious surface areas, and forest cover). This information is used in the Countywide Stream Protection Strategy to help assign watersheds to different management categories with specified management tools.

Biological Data: A cost-effective way to make it "real"

The Montgomery County DEP found that the bioassessment component of the stormwater monitoring program was invaluable in promoting public awareness and involvement. The biological monitoring results enable DEP staff to explain stream quality in terms of fish and aquatic insects supported by the stream, including how the habitat, water quality, and upland watershed conditions all impact the biological life. This type of information has been more comprehensible to the public than chemical monitoring data. In addition, because the Countywide Stream Protection Strategy relies on the use of subwatersheds, emphasis was placed on the small neighborhood streams to which people could easily relate. The county has also developed an extensive public outreach and education program, focusing on citizen and business roles in pollution prevention and stream stewardship. Individual volunteers, non-profit agencies, school groups, and businesses are directly involved in stream monitoring, riparian tree plantings, and other "hands-on" projects that promote an understanding of ecology and the impacts of stormwater in their neighborhood stream.

Montgomery County Public Outreach Programs

Stream Teams: DEP worked with the public schools to develop a program where selected classes (grades 4 -12) adopt segments of a neighborhood stream, monitor them three times a year, analyze the data, and report to DEP. Stream Teams are often invited to present their findings to elected officials, citizen groups, and environmental forums. As of the 1998/1999 school year, 100 stream team schools participated in the monitoring of over 140 stream stations.

Pipe Detectives: DEP trains volunteers to observe and report illicit discharges observed from storm drain outfalls.

Clean Water Partners: Private industrial and commercial sites voluntarily pledge to implement pollution prevention in their operations and to conduct a "watershed awareness activity," such as adopting a stream, hosting a watershed cleanup event, or distributing pollution prevention information to customers.

The use of bioassessment data has impacted the "bottom line" - both directly and indirectly. The DEP has been able to biologically monitor approximately 346 sites providing information covering nearly 1500 miles of streams, plus operate two automated storm event sampling stations. This has been accomplished for approximately the same amount as spent by other jurisdictions who have focused on runoff event chemical sampling at four to eight stations. In addition, the added scientific and educational value of the biological data has promoted support within the business community and citizenry to fund the major increases in the county's stormwater programs which were needed to respond to the federally mandated NPDES stormwater requirements.

One final example of a success story resulting from Montgomery County's comprehensive work on stormwater retrofit, stream restoration, and public outreach activities is Sligo Creek. Many of the small headwaters of this highly urban stream system had been piped prior to the early 1970s, with no mitigating stormwater or sediment controls. Conditions were severely degraded, and only two fish species were present. After implementation of erosion and runoff controls, as well as intensive habitat restoration, citizens began capturing and returning fish and amphibians that were formerly native to Sligo Creek from other watersheds. As a result, this system now supports more than 13 species and its restoration has brought the county national recognition. The development of successful pilot programs such as this has helped the county to attract substantial grant and cost-share funding from state and federal agencies for additional protection and restoration.

Lesson Learned

For the same cost as chemical monitoring, bioassessment yielded a more comprehensive picture of stream quality and added scientific and educational value to Montgomery County's stormwater control program.

Additional Information

Montgomery County's Stream Monitoring Program
Keith Van Ness ( Senior Aquatic Ecologist at DEP (240-777-7707)
Visit the Montgomery County DEP website Exit

Watershed Management Program
Cameron Wiegand, Chief, Watershed Management Division, at DEP (240-777-7780) or


Montgomery County Department of Environmental Protection in Cooperation with Maryland-National Capital Park and Planning Commission, 1998. Montgomery Countywide Stream Protection Strategy.

Plaflan, J.L. , M.T. Barbour, K.D. Porter, S.K. Gross, and R.M. Hughes. 1989. Rapid Bioassessment Protocols for Use in Streams and Rivers: Benthic Macroinvertebrates and Fish. EPA/444/4-89-001. U.S. Environmental Protection Agency, Washington, D.C.

Van Ness, Keith, K. Brown, M. Haddaway, D. Marshall, and D. Jordahl. 1997. Montgomery County Water Quality Program, Stream Monitoring Protocols, Montgomery County Department of Environmental Protection.

Van Ness, Keith. 1997. Analysis of the Habitat, Physical, and Biological Monitoring Data for the Little Falls, Paint Branch, Northwest Branch, Upper Rock Creek, Lower Rock Creek, Little Paint Branch, Cabin John Creek, and Watts Branch Watersheds. Montgomery County Department of Environmental Protection.

Wiegand, C. 1997. 1997 National Stormwater Control Program Excellence Awards Application, prepared by the Watershed Management Division, Department of Environmental Protection, Montgomery County, MD.

Top of Page