Water Resources Research Act Program

Details for Project ID 2006DC79B

Effect of Best Management Practices on contaminant levels in storm water runoff to the Anacostia River

Institute: District of Columbia
Year Established: 2006 Start Date: 2006-03-01 End Date: 2007-02-28
Total Federal Funds: $15,000 Total Non-Federal Funds: $65,890

Principal Investigators: Charles Glass

Project Summary: This project is designed to examine the effectiveness of best management practices (BMPs) to retain stormwater pollutants from runoff over impervious surfaces. The federal government and local government agencies have funded, and/or partnered with other organizations funded, the construction of many bioretention cells, sand filters, and other BMPs for the prevention of stormwater contaminated runoff in Washington D.C. in an effort to prevent the further degradation of the Anacostia and Potomac Rivers, as well as Rock Creek. There is a need to further understand how these BMPs are performing, which are the most effective, and if design improvements are possible for future BMP installations. Combined sewer overflows (CSO) continue to occur throughout major cities in the Northeast, Great Lakes, and Northwest regions of the U.S., primarily as a result of rainwater that is diverted from roads, parking lots, and the roofs of buildings during storm events [1]. The rapid transport of water away from the built environment to natural water bodies has dominated engineering for the past 130 years, since the recognition that pathogens in wastewater caused several human diseases. In older cities with combined sewers the continued replacement of natural surfaces with impervious ones leads to greater amounts of stormwater runoff. The contamination of natural water bodies leads to the destruction of habitat potentially leading to negative human health impacts Griesel and Jagals [2]. Developing best management practices to prevent rain water contamination, remove pollutants before the runoff enters the combined sewer system, and retain or detain the movement of water in a decentralized fashion can potentially mitigate CSO events. Urbanization creates impervious surfaces such as roads, sidewalks, highways, rooftops, and parking lots that result in an increase of stormwater runoff at the expense of infiltration. The stormwater runoff quickly flows over those impermeable surfaces and accumulates toxic pollutants such as heavy metals [3, 4, 5] generated by automobile use, weathering of building materials and atmospheric deposition Davis et al [6]. A nationwide U.S. urban study showed that heavy metals were by far the most prevalent pollutant constituents of urban stormwater runoff Cole et al [7]. Due to its toxic content, the storm water runoff when discharged to a stream, severely impacts the quality of natural water systems by causing a threat to aquatic life and human health, and also flooding and erosion. As a result, urban stormwater runoff has been identified as one of the most significant water pollution problems in the United States Wiginton et al [8]. To address the problem of surface water pollution from urban stormwater runoff, a number of engineered and managed natural systems have evolved and are being offered as best management practices (BMPs) for low impact development. They are part of the United States Environmental Protection Agencys (USEPA) effort to regulate the release of pollutants into natural aquatic environments through water quality standards set forth by the National Pollutant Discharge Elimination System (NPDES). A stormwater BMP is a device, practice, or method used to remove, reduce, retard, or prevent targeted stormwater runoff pollutants from reaching receiving waters in the most cost-effective manner. In the early 1990s, Prince Georges County, Maryland began developing and promoting a natural-based stormwater BMP system known as bioretention (or rain garden) [9]. Bioretention is a simple but effective way to improve the quality of stormwater runoff from developed areas such as parking lots, in order to minimize surface water impacts. Bioretention is a porous sand/soil media, supporting a vegetative layer, with a topping layer of hardwood mulch. Water quality enhancement occurs through the bioretention facility via biological, chemical and physical processes including phytoremediation, precipitation, adsorption, complexation, microbial activity, decomposition, sedimentation, filtration, and volatilization. In urban environments these systems are typically designed by filling a concrete box with gravel, sand, planting soil, a top layer of mulch, and various species of water loving plants. Currently little is known with regard to the field performance of bioretention cells. Few researchers have evaluated the performance of best management practices with actual stormwater runoff Davis et al [10].