According to the U.S. Environmental Protection Agency (EPA), the restoration of Sligo Creek by the Montgomery County Department of Environmental Protection (DEP) has improved water quality and aquatic life and is a national success story. By 1985, stormwater runoff and extensive habitat destruction in this highly urbanized tributary to the Anacostia River had contributed to the elimination of all but four of the most pollution-tolerant fish species. Sligo Creek’s condition received a rating of “poor” on a DEP biological assessment of the stream’s health. DEP efforts improved the rating to “fair” by improving habitat that is naturally sustaining 14 fish species and contributing to reduced pollutant loads for phosphorus, nitrogen and sediment.
“The success we are seeing in Sligo Creek is proof positive that we can improve the neglected streams in our beautiful County,” said DEP Director Bob Hoyt. “Our success spurs us to continue working even harder to ensure that the next generation enjoys the benefits of healthy and safe water.”
A goal of watershed restoration in highly developed areas is to reduce the negative impacts of stormwater on streams. In unrestored or older watersheds, intense rainstorms can increase the amount and rate of water flowing directly into streams and creeks, causing scouring of streambeds, destruction of biological habitats and increases in pollutant loads from unchecked runoff. DEP has implemented stormwater management practices on 1,425 acres (48 percent) of the upper Sligo Creek sub-watershed, resulting in a 41 percent reduction in peak stream flow discharge. This has led to improvements in water quality, streambed and bank stability, in-stream habitat, and a more abundant benthic macroinvertebrate community that helps support increased fish populations.
The Sligo Creek restoration program, led by DEP, began as a cooperative partnership between the County, the Maryland Department of the Environment (MDE), The Maryland-National Capital Park and Planning Commission, the Washington Metropolitan Council of Governments, the Interstate Commission on the Potomac River Basin, U.S. Army Corps of Engineers and EPA.
Work on the watershed began in 1989. During this first phase, DEP transformed a dry stormwater pond, which collects runoff from 805 acres of highly impervious commercial and residential properties, into a three-celled, extended-detention wet pond with wetland plantings. The wet pond improved appearance, provided fish and wildlife habitat, and captured sediment and trash. Below the pond, DEP restored 1,000 linear feet of downstream aquatic habitat by creating two vernal pools for amphibian breeding, and repaired 1,200 feet of stream banks.
In Phase II (1992–1994), DEP rebuilt another stormwater pond, serving 434 acres, as a two-celled, extended-detention wet pond/marsh. Other projects included restoring 2.5 miles of aquatic habitat, creating a quarter-acre marsh, replanting five acres of forest and implementing 19 small, aquatic habitat improvement projects. To assist recolonization beyond an existing fish blockage at I-495, native fish species were captured in neighboring Northwest Branch and released into the upper Sligo Creek. These fish were able to disperse throughout the upper Sligo Creek mainstem.
DEP began Phase III in 1996, constructing a one-acre detention wet pond at Sligo Creek Golf Course to capture stormwater runoff from 70 acres, including a one-mile portion of Interstate 495.
During Phase IV (1999), DEP created two stormwater wetlands. Restoration work in middle Sligo Creek helped return stream segments to the more natural conditions that support aquatic life habitat needs.
Phase V (2005–2007) consisted of installing low impact development stormwater management features and bioretention systems. DEP also established a new goal to improve the Index of Biotic Integrity (IBI) from a “poor” to a “fair” rating. Native fish species that were indicators of fair to good stream conditions were identified in nearby Anacostia streams and then captured and released into Sligo Creek. These capture and release efforts included public environmental education opportunities. DEP biologists did most of the fish releases over time, monitoring the success and movement of the fish into other portions of Sligo Creek. Since 2007, large areas of Sligo Creek have received a ‘fair’ stream condition rating using the fish IBI.
Current efforts in Phase VI (2010–present) involve focusing restoration efforts within small catchments where intensive neighborhood projects will continue to cumulatively improve conditions in the Sligo Creek watershed. One such small catchment is the 65 acre Breewood Tributary, where a comprehensive restoration effort includes installing rain gardens and bioswales; replacing mowed grass areas with vegetation on public and private properties; and an outreach campaign to educate residents’ about reducing runoff impacts to this tributary.
Efforts to address water quality and habitat problems in Sligo Creek resulted from the 1987 enactment of the Anacostia Watershed Restoration Agreement, an evolving inter-jurisdictional blueprint that has guided restoration efforts across the Anacostia watershed, including Sligo Creek.
About $3 million (excluding monitoring costs) has been invested in the upper Sligo Creek restoration effort, including $1.8 million from the Montgomery County capital budget, $1 million from MDE’s Small Creeks and Estuaries Reserve cost share program, and $256,000 from the U.S. Army Corps of Engineers.
To view the Sligo Creek success story, go to: http://water.epa.gov/polwaste/nps/success319/md_sligo.cfm. For more information about DEP’s watershed programs, go to www.montgomerycountymd.gov/dep and click on Water.
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