The potential for natural attenuation of petroleum-hydrocarbon and chlorinated volatile organic compound contamination in ground water was investigated at a gas-turbine manufacturing facility in Greenville, S.C. Examination of benzene migration involved integrating hydrogeologic, geochemical, and microbial parameters in a ground-water flow and solute-transport model. The natural attenuation potential of other compounds was examined using geochemical observations.
Modeling results suggest that natural attenuation processes probably will be adequate to prevent migration of benzene from the Test Stands contamination to Little Rocky Creek at concentrations greater than 5 mg/L. The potential for naphthalene and free-phase petroleum transport to the creek could not be determined because of limited historical data.
A substantial amount of chlorinated volatile organic compound dechlorination has taken place in the aquifer system. Most of the dechlorination appears to have taken place in zones where the chlorinated volatile organic compound contamination commingled with petroleum hydrocarbon contamination. Dechlorination in these zones of maximum degradation potential, however, is insufficient to prevent tetrachloroethene migration into downgradient areas where tetrachloroethene degradation is reduced. Thus, natural attenuation is not a suitable remedial alternative for contamination from the Diesel Pump Station or the Service Building.
By analogy, these data also provide a field experiment to test the potential of an engineered approach to optimize biodegradation rates in source areas by allowing the chlorinated aliphatic compounds to mix with oxidizable organic substrate. The data suggest that such an approach would be inadequate to completely prevent transport of tetrachloroethene in this aquifer system.
--- 1998
By Don A. Vroblesky, Matthew D. Petkewich, Paul M. Bradley, and John F. Robertson