Quantitative analysis of fecal contamination in stormwater conveyance systems and the effects of storm drain discharge on beach water quality in Wrightsville Beach

Fecal contamination in stormwater runoff is a concern for public health in coastal beach communities. Historical data collected by the Town of Wrightsville Beach has previously indicated that fecal indicator bacteria (FIB - Escherichia coli (E. coli) and Enterococcus spp.) concentrations frequently exceeded USEPA recommended water quality standards during and after storm events. Using both culture-based methods and quantitative PCR (qPCR), water samples from the storm drain systems of two problem watersheds were analyzed for FIB concentrations in addition to quantification of specific sources of fecal contamination from humans, gulls and dogs. Human and gull fecal contamination were both frequently quantified during the storm events (n=16). Significant correlations were observed between 1 hour antecedent rainfall and the human-associated fecal Bacteroides marker (r = 0.17, p<0.05, n=149), indicating the potential for future real-time beach management decisions to be made based on rainfall. An across beach study was then conducted to assess the dispersion of the stormwater plume during a typical storm event. The data demonstrated that significant levels of contamination were observed up to 200 m downcoast of the point of discharge, including quantified human and gull fecal contamination in the receiving waters. These results provide a valuable platform for the Town of Wrightsville Beach to mitigate sources of fecal contamination and prioritize strategies for improved public health notification.