An Investigation into the Water Quality of the Charleston Peninsula Storm Drains

Since the late 1980's, the South Carolina Department of Health and Environmental Control (SCDHEC) has expressed concern over extremely high fecal coliform counts found in several of the many storm drains that discharge from peninsular Charleston (City of Charleston, 1998). Although the City of Charleston is responsible for the fifty-plus storm drains, Charleston Water System wants to determine if the fecal contamination is of human origin, indicating possible cross connections between the sanitary sewer system and the stormwater drainage system. Charleston Water also wants to determine the overall quality of the water being released from the storm drains to see how these diffuse sources may affect the total maximum daily load (TMDL) of Charleston Harbor. An objective of this study is to determine the levels of biochemical oxygen demand (BOD) and ammonia as N being discharged from the storm drains, indicating possible pollution that may affect the calculation of the TMDL. Another objective of this study is to determine if the fecal pollution (indicated by fecal coliform and enterococci numbers) is human vs. nonhuman in origin, as evidenced by developmental microbial source tracking (MST) technology. Five storm drains and two background receiving waters spanning the Charleston peninsula were chosen as sampling sites. Analyses performed by Charleston Water included: BOD, ammonia as N, fecal coliform by membrane filtration, and enterococcus by Enterolert™. Samples were also tested by the National Oceanic and Atmospheric Administration's (NOAA) Center for Coastal Environmental Health & Biomolecular Research (CCEHBR) for somatic and male-specific coliphages, human-associated F+RNA coliphages, and norovirus; samples were tested for the human-associated archaean Methanobrevibacter smithii by the University of Southern Mississippi in Hattiesburg, MS to help determine the origin of the fecal contamination. Measured BOD concentrations and ammonia as N concentrations indicate low concentrations and overall good water quality. As expected, fecal coliform and enterococci counts are extremely high, indicating fecal pollution. Evidence of human fecal contamination has been identified in two storm drains as indicated by NOAA and the University of Southern Mississippi using MST technology, implying possible cross connections between the sanitary sewer system and stormwater drainage system in these localized areas.