Reducing Stormwater Bacteria Loads to North Carolina Ocean Recreational Areas Using a Dune Infiltration System

Coastal towns traditionally discharge stormwater containing bacteria and pathogens to the ocean via ocean outfalls, increasing the potential for serious diseases to recreational swimmers. To combat this risk, an innovative coastal BMP, a Dune Infiltration System (DIS), was designed and installed at two locations in Kure Beach, N.C. to divert stormwater from outfalls into the dunes. Post-construction monitoring of these systems during 25 storm events in 2006 showed that this design was economically and technically feasible, because 97% of the stormwater was diverted into the dunes, the dunes remained structurally stable, and Enterococcus concentrations entering from the outfalls were reduced by over 97%. However bacterial transport surrounding the system remained poorly understood, which limited the certainty at which this system could be recommended for further implementation. Therefore, a series of additional water table and water quality wells were installed at each of the systems, and in a nearby control dune, during the summer of 2007. After six-months, bacterial concentrations in the groundwater at the dune-beach interface near the dune infiltration sites are similar to that of the control area.