Uranium, Radium, and Radon in Well Water in South Carolina: Distribution and Problems

South Carolina, despite being a small state, possesses a wide range and diversity of hydrogeologic conditions, generally arranged into geologic belts or physiographic provinces. These distinct areas range from the mountains and piedmont with crystalline metamorphic and igneous rocks with major geologic structural features, to a broad coastal plain with sand and limestone aquifers (Fig. 1). Accompanying this physical diversity are some special problems and risks to ground-water users of each region, all of which must be recognized in statewide groundwater and drinking-water management. One type of risk to users that has strong geographical associations is the scattered—but not random at the state scale—problems of natural mineral-derived radioactive elements dissolved in the ground water, problems that are significant both numerically (by number of wells) and susceptible area (in toto) . Here a problem means concentration above the US EPA drinking water standard. Essentially, the overall problem exists mainly as uranium in excess in parts of the piedmont and its border in the Appalachian “foothills” and radium in excess in inner parts of the coastal plain. Some outliers and other local problem areas also exist and are important though. Radon at potential problem levels is wider spread. Main concern with uranium, radium, and radon is for home wells, because public supply wells have been or will be tested routinely and any problem has been or will be identified and eliminated. A problem, even a severe one, may exist and persist unknown in home wells for decades or occasionally generations.