Bacterial Removal Efficiency of a Bioswale Located in Lockwood Folly, a Coastal Watershed in North Carolina

NC Department of Transportation (NCDOT) has obtained, through partnerships with private sector, an engineered soil to enhance removal of fecal bacteria when used in conjunction with stormwater Best Management Practices, such as bioretention cells. The efficacy of this media is being tested at a site in Lockwood Folly, NC where a TMDL for fecal coliforms was approved by the NC Department of Natural Resources in 2010 to address shellfish harvesting impairments in the nearby estuary. Mechanisms for bacterial removal are a\ributed to: (1) retention of particles to which microbes adsorb and (2) mortality due to grazing by protozoans harbored by the soils. Funding is being provided by NC DOT as part of a program to evaluate pollutant removal efficiencies of various BMPs for road runoff treatment. NCDOT’s NPDES permit requires the retrofit of 50 stormwater BMPs in each 5 year cycle; they optimize their retrofits through results of research. The results of this assessment work are of much interest to South Carolina due to the large number of monitoring sites with fecal bacteria impairments that are located in settings similar to the Lockwood Folly watershed, the relatively low cost of the media, and the option of retrofitting existing BMP\u27s to enhance bacteria removal