Natural attenuation of chlorinated aliphatics at the Naval Air Engineering Station, Lakehurst, NJ

The U.S. Navy is currently in the second year of a three year study to verify the existence and evaluate the effectiveness of natural attenuation processes in degrading a large chlorinated aliphatic plume in Areas I and J of Naval Air Engineering Station (NAES), Lakehurst, NJ. The preliminary results of the study, which began in 1996, indicate that natural attenuation processes, primarily in the form of intrinsic biodegradation, are active at the site and are impacting plume migration. The presence of both anaerobic and aerobic intrinsic biodegradation is supported by the distribution of chlorinated aliphatic compounds and geochemical conditions within the plume. Biotransformation products such as cis-1,2-dichloroethene (cis-DCE), vinyl chloride (VC), 1,1-dichloroethane (1,1-DCA), and chloroethane (CA) produced by the reductive dehalogenation of parent compounds tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA) are present in anaerobic zones near source areas, but are preferentially attenuated in down-gradient aerobic zones, consistent with the aerobic oxidation of those compounds. MODFLOW and MT3D computer codes were used jointly to predict the future migration of the contaminants in the aquifer. The model calibrated well against observed data, but its predictive capability is limited by the inability of the biodegradation submodel to account for the complex multi-species biodegradation kinetics present at the site. Subsequent modeling using the biologically-reactive, multi-species transport model RT3D is expected to improve our ability to more precisely predict the impact of natural attenuation on the contaminant plume.