THE DEVELOPMENT OF CHEMICAL-SPECIFIC, RISK-BASED SOIL CLEANUP GUIDELINES RESULTS IN TIMELY AND COST-EFFECTIVE REMEDIATION

Millions of dollars of limited state cleanup funds are spent each year in New Hampshire to identify, sample, excavate, and treat thousands o f tons of contaminated soil. Cost analyses of numerous sites indicated that soil remediation costs alone reach upwards of $300,000.00 per si te. The New Hampshire Department of Environmental Services ''Interim P olicy for Management of Soils Contaminated from Spills/Releases of Vir gin Petroleum Products'' (DES, 1989, 1991) set conservative remediatio n goals based on total petroleum hydrocarbons in 1989 using the Leachi ng Potential Analysis method (California Luft Manual, 1989). A current review of available literature and several case histories indicated t hat chemical-specific soil cleanup levels may be more appropriate for establishing remedial goals. New chemical-specific soil cleanup guidel ines using a risk-based approach have been developed. These new guidel ines are conservatively based using two principal considerations: (I) an assumed soil exposure scenario that estimated the human health risk s associated with potential long-term exposure to site soils via inges tion, inhalation and dermal contact and (2) the estimated fate and tra nsport of chemicals of concern in the soil unsaturated zone. The first consideration assumed a total cancer risk that did not exceed 1 x 10( -6). The second consideration employed the use of the SEasonal SOIL Co mpartment (SESOIL) model which simultaneously models water transport, sediment transport, and pollutant fate (US EPA, 1981). Several state s oil standards from Oregon, Wisconsin, Massachusetts, and other states were extensively reviewed in order to develop a level of confidence th at use of the SESOIL model was appropriate. A series of ''sensitivity' ' analyses was also performed in order to evaluate the response of the model to changes in various input parameters unique to New Hampshire' s hydrogeologic conditions. Generic soil cleanup guidelines were devel oped for 24 petroleum-based volatile and semivolatile chemicals of con cern to be applied statewide. Site-specific soil cleanup guidelines wi ll be allowed if it can be demonstrated that insertion of site-specifi c data into the model will not adversely affect groundwater quality. A s a result of the above processes, timely and much more cost-effective remediation will be achieved while still maintaining a high degree of protection of the groundwater quality and human health.