The Control of Pollution in Highway Runoff through Biofiltration Volume II: Testing of Roadside Vegetation

field monitoring program was begun in 1991, testing the pollutant removal efficiency of selected best management practices (BMPs) to obtain detailed information for design guidelines for stormwater BMPs included in the Virginia Department of Transportation's Stormwater Management Manual. This report summarizes Phase 1•I of this project. Data from a grassed highway median swale monitored in an earlier study was compared to data from the swale monitored in this phase. The swale in this study had no checkdam and differed from the earlier swale in slope, traffic volume, and vegetation height, all of which affected pollutant removal. Manual and automatic sampling techniques were used to monitor highway runoff flowing into and out of the grassed swale. Pollutant removal efficiencies were calculated on a mass balance method. Also, the pollutant removal ability of a short buffer strip receiving highway runoff was examined. Pollutants monitored included total suspended solids, chemical oxygen demand, total phosphorus, and zinc. The results of the field monitoring program suggest that properly designed short buffer strips and swales with check dams can remove pollutants from highway runoff.