Date of Award
Master of Science (MS)
Dr. Cindy M. Lee, Committee Chair
Dr. Lawrence Murdoch
Dr. James Castle
Substantial research focused on Lake Hartwell and a major tributary, Twelvemile Creek, has provided information regarding surface transport, deposition, and biological interactions of PCBs. However, little is understood about the transport of PCBs in groundwater between the contamination site (Sangamo Weston Superfund Site in Pickens, SC) and Town Creek, a tributary to Twelvemile Creek located less than 500 m south of the contamination site. The objectives of this thesis were to 1) locate and measure groundwater influx to Town Creek, 2) determine the concentrations of PCBs in groundwater, 3) identify the colloids present in groundwater and surface water, 4) determine if colloids are adsorbing PCBs, and 5) characterize the basic geology and hydrogeology between Town Creek and the Sangamo Weston Site. Locations of possible groundwater input to the stream were identified using distributed temperature sensing (DTS) fiber optics placed along ~230 m length of Town Creek down gradient of the Sangamo Weston site in September 2011. A follow up seepage meter and mini-piezometer test in the summer of 2012 was performed to confirm if the DTS was identifying groundwater. Polyethylene strips were used to adsorb dissolved PCBs in groundwater samples collected from two bedrock wells (701 and 702) north of Town Creek, and gas chromatography was employed to determine the concentrations. Colloids from surface and groundwater samples were filtered through 1 μ and 100 kDa filters, respectively, and characterized using FT-IR and SEM. The geology along the creek was mapped for lithology and structure, and hydrogeological data from the site were used to develop hydraulic head maps for both saprolite and bedrock wells. Results from this research confirmed groundwater inflow between 185 and 210 m upstream of Reece Mill Bridge using seepage meter measurements, and identified a possible location between 128 and 146 m upstream of the bridge with the DTS. Seepage meter measurements indicated an average flux into the stream of 7.63x10-6 m/s and mini-piezometers confirmed upward flow into Town Creek. PCB concentrations in groundwater wells averaged 1800 ng/L in well 701 and 6535 ng/L in well 702. Colloid characterization recognized gibbsite, kaolinite, and iron (hydr)oxides in surface water, and montmorillonite and manganese (hydr)oxides in groundwater. The montmorillonite is likely an artifact of the well construction. Geologic mapping documented a thrust fault, folds, fractures, and igneous intrusions along the stream, with rock predominantly made up of gneiss. The head maps produced indicated that groundwater should flow down gradient from the Sangamo Weston site to the Town Creek study area through saprolite if isotropic and homogeneous hydraulic conductivities are assumed. Head measurements from wells indicated flow towards the stream and seepage meter measurements confirmed flux into the stream consistent with other streams in the Piedmont. Groundwater data suggest that significant concentrations of PCBs are present at the site, and surface water PCB concentrations suggest that groundwater is entering the stream. However, groundwater colloid data may be skewed by the bentonite used during well installation. Initial study of colloid facilitated PCBs has found that adsorption does occur in the groundwater collected, but additional study is required to quantify concentrations.
Hahn, David, "Charaterization and Locating PCB-Contaminated Groundwater Entering a Stream Overlying Faulted and Folded Crystalline Rock" (2012). All Theses. 2516.