SURFACE WATER CONTAMINATION FROM URBAN STORMWATER RUNOFF IN CHARLESTON, SC

Rapid urbanization in coastal cities in the southeastern US has resulted in nuisance flooding during periods of high tide or heavy rainfall. The many impervious surfaces result in excess runoff into the Charleston Harbor. Currently there are not many studies that have focused on the water quality of this runoff and the resulting problems in the final receiving water bodies such as stormwater retention structures, streams, or estuaries. Therefore, we focused on analyzing event-based stormwater sampling in Charleston, South Carolina to identify broad sources of water contamination in a typical urban setting.

Sampling sites were identified using high resolution elevation data, known hotspots of flooding during rainfall or higher than normal tides. Water sampling involved collection of sheetflow or standing water using established methods. Residential, commercial, tourist areas of the Charleston peninsula were targeted for sampling.

Major ions using ion chromatography, trace metals using inductively coupled plasma mass spectrometry, and fecal indicator bacteria using an IDEXX quantitray method were analyzed for this study. Preliminary data suggest high ion, trace metal, and fecal indicator bacteria levels in the initial runoff. Numerous diffuse and nonpoint sources reflect these levels of chemical and bacterial indicators. It is expected that this compromised water quality impacts the Charleston harbor and its ecosystem. More data is being collected to produce a comprehensive map of contamination concentrations during storm events all over the peninsula, in order to identify the most problematic sources of contamination.