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Influence of subsurface drains on contaminant source and fate, Site 45, Marine Corps Recruit Depot Parris Island, South Carolina
Project Number: 2519-CH501
The U.S. Geological Survey (USGS) has begun examination of particular aspects associated with groundwater contamination by chlorinated solvents (Tetra Tech NUS, Inc., 2004, 2005) at Site 45, Marine Corps Recruit Depot (MCRD), Parris Island, South Carolina. The groundwater contamination plume is characterized by two major lobes, hereafter referred to the southern and northern parts of the contamination plume. USGS activities at the site supplement existing ongoing investigations, and examine some hydraulic issues not previously examined, with the goal of optimizing remediation.
At this site, a chlorinated solvent plume in groundwater originates from an area where there is no history of contaminant use, and the plume appears to be headed toward a housing facility.
Objectives of this study are to:
In 2007, preliminary work by the U.S. Geological Survey at this site showed that the contamination appears to have originated by leakage from a sanitary sewer that drained a dry cleaning facility that had a history of spills, that rapid biodegradation of the contamination takes place in the aquifer, and that storm sewers beneath the water table intercept the contamination prior to transport to the housing facility. In 2008, Specific tasks will be to resolve uncertainties in the contaminant distribution near the source area by installing temporary wells, determine the potential affect on surface water by collecting and analyzing surface-water samples, examining the potential for contamination of the deeper aquifer by installing new wells, examining natural attenuation aspects by sampling existing and new wells, and producing a report.
Resolving uncertainties in the contaminant distribution near the source area will be accomplished by installing and sampling approximately 19 temporary wells in that area. Determining the potential influence on surface water will be accomplished by collecting sediment and water samples at multiple points where the storm sewer discharges to a surface-water body. Examining the potential for contamination of the deeper aquifer will be done by installing and sampling three new monitoring wells near the source area to a depth immediately below a confining bed at the base of the contaminated shallow aquifer. Evaluation of natural attenuation aspects will be done by sampling existing monitoring wells along the path of contaminant transport.
A better understanding of the influence of subsurface drains on contaminant movement will allow other sites to adequately address this aspect when characterizing groundwater contamination. The influence of subsurface drains is an often overlooked aspect. As shown by this investigation, subsurface drains can be an extremely influential influence on the source, transport, and fate of groundwater contamination.