OCCURRENCE OF ETHYLENE DIBROMIDE (EDB), DIBROMOCHLOROPROPANE (DBCP), OTHER VOLATILE ORGANIC COMPOUNDS, AND RADIUM IN GROUNDWATER FROM THE UPPER COASTAL PLAIN AQUIFERS NEAR MCBEE, SOUTH CAROLINA

Between 2010 and 2012, samples were collected from several public supply wells (PSWs), irrigation wells, and springs in the upper Coastal Plain Crouch Branch and McQueen Branch aquifers near the small town of McBee in northeastern South Carolina. Water samples were collected and analyzed for volatile organic compounds (VOCs), including ethylene dibromide (EDB) and dibromochloropropane (DBCP), and total radium (as ²²⁶Radium [²²⁶Ra] and ²²⁸Radium [²²⁸Ra]). EDB, DBCP, and ²²⁶Ra and ²²⁸Ra were previously detected above U.S. Environmental Protection Agency Maximum Contaminant Levels (MCLs) in groundwater samples collected by the South Carolina Department of Health and Environmental Control. During this current investigation, EDB and DBCP were detected above their MCLs in groundwater samples from some public supply and irrigation wells, and in some springs. Multiple VOCs were detected at concentrations at or below method reporting levels (MRLs) in several wells, and the solvent trichloroethylene was detected in one PSW near the future location of rapid municipal-wastewater infiltration galleries. Radium was detected in most groundwater samples, but at levels below the MCL of 5 picoCuries per liter (pCi/L). Finally, concentrations of chlorofluorocarbons (CFCs) measured in groundwater samples from PSWs sampled in 2010 indicate an average recharge age of about 40 years. The CFC-based recharge ages were used with numerical modeling to identify recharge locations and potential contaminant source areas.