ATTENUATION OF A HYDROCARBON CONTAMINANT PLUME ON THE CUMBERLAND PLATEAU OF TENNESSEE

In 1994, a leaking underground storage tank was discovered on the grounds of the University of the South in Sewanee, Tennessee, located on the southern Cumberland Plateau. The site is characterized by sandy loam soils up to 10 feet deep resting atop Pennsylvanian conglomerate. Ground water occurs in perched, discontinuous, seasonal aquifers within the soil where flow is controlled by topography of the bedrock surface. Concentrations of benzene, toluene, ethylbenzene, and xylene (BTEX) in the ground water were measured in several monitoring wells and found to form a contaminant plume extending 400 feet down gradient from the tank. The highest concentrations of BTEX were localized in two areas: one near the tank (20,000 ppb) and the other about 300 feet down gradient from the source of the leak (30,000 ppb). In 2004, new monitoring wells were installed to delineate the current plume shape and BTEX concentrations. The original plume appears to have shrunk, splitting into two seperate plumes surrounding the high-concentration zones found in the initial study. As one of the first studies of hydrocarbon contamination within a seasonal aquifer atop the Cumberland Plateau, this investigation may help predict the behavior of contaminant plumes in similar settings.