BMP Pollutant Removal Efficiency

Stormwater Best Management Practices (BMPs) are receiving national acceptance as a viable means of controlling excess runoff due to rainfall events. BMPs allow for Stormwater to move directly to the localized groundwater table via infiltration and thereby return the post-development outflow hydrograph peak-flow and volume to pre-development conditions. Another advantage to using BMPs instead of a traditional detention basin is thought to be the potential to remove non-point source pollutants accumulated in the surrounding developed areas. Theoretically pollutants are carried into the BMP with the excess runoff and are allowed to infiltrate into the ground, thereby improving the quality of the surface water released by the BMP back into the environment. Additionally, pollutants also have the potential to be caught in the underlying soil layer and removed from the infiltrating water as it makes its way to the groundwater table. A water quality investigation was completed on three different types of BMPs; a bio-infiltration pond, a Stormwater wetland, and a pervious concrete surface with underlying rock bed, in order to ascertain the pollutant removal efficiency of each of the various BMPs. The investigation involved a statistical analysis of the inflow water quality concentrations versus the outflow and infiltrating concentrations at varying depths beneath the ground surface. Constituents analyzed included: nitrogen, phosphorous, chloride, suspended solids, dissolved solids and Ph. The results of the analysis are mixed at each site with the Stormwater wetland having the greatest pollutant removal efficiency for surface water flows, and the bio-infiltration pond having the greatest pollutant removal efficiency for infiltrating waters.