Abstract, Live Poster Session (BACK)
The Water Quality Promise of the Regenerative Stream Channel
(Click to view poster)
District of Columbia Department of the Environment
Authors: Suzanne Wald, Steve Saari & Stephen Reiling
The District of Columbia will install two Regenerative Stream Channel systems (RSCs) in an ultra-urban watershed and monitoring their efficacy in an effort to establish this stormwater management technique as a Bay Program Best Management Practice (BMP). RSC systems are open-channel, sand seepage filtering systems that utilize a series of shallow aquatic pools, riffle weir grade controls, native vegetation and an underlying sand channel to treat and safely detain and convey storm flow. In addition, RSCs convert stormwater to groundwater via infiltration at stormwater outfalls and other areas where grades make traditional practices difficult to implement. Despite data showing that RSCs are effective at reducing flow velocities, there is little documentation of their capability of reducing pollutant loads.
DDOE has contracted the University of Maryland Center for Environmental Science, Chesapeake Biological Lab (CBL) to monitor these systems and provide analysis. In January 2013, CBL began pre-installation monitoring for concentrations of nitrate, ammonium, total dissolved nitrogen, total dissolved phosphorous, total suspended solids, dissolved oxygen, cadmium, copper, lead, zinc, iron and bacteria; monitoring of subsurface water recharge and water temperature; and habitat health using Rapid Biological Assessment. DDOE staff will employ photo point monitoring to document both ecosystem change and RSC system stability over time.
CBL will use a paired-catchment analysis, studying the same set of parameters at a stream and watershed of similar character that is not slated for restoration. Because the District also plans to restore streams in areas of the District located in the Coastal Plain, CBL will duplicate the paired-catchment monitoring effort using a planned RSC stream restoration in the Anacostia watershed. At all sites, the contributing sewersheds are very similar, containing 20 to 30% impervious surface combined with highly-managed landscaping. What differs in the Coastal Plain sites is the receiving streams cut through highly erodible soils to plummet vertically 30 or more feet on their descent to the Anacostia River.
In both paired catchment studies, monitoring will span a period of one year pre-implementation and at least one year post-implementation of the RSC structure, but will continue as long as required by our restoration permit.