Remediation of DNAPL groundwater contamination at a former landfill abstract

A landfill in western Montana was used for disposal of laboratory waste for a period of five years in the early 1980s. Wastes included chloroform and other chlorinated hydrocarbons which are heavier than water and only slightly soluble in water. These dense non-aqueous phase liquids (DNAPLs) migrated to the water table and eventually created a contaminant plume about three-quarters of a mile long in a residential and commercial area dependent on the aquifer for its water supply. Remediation. efforts to date have consisted of excavation of contaminated soil, treatment of soil on-site, and pumping and treatment of groundwater. An extensive drilling program was undertaken to delineate the extent of ground-water and soil contamination. 75,000 cubic yards of contaminated soil and overburden were excavated and the contaminated soils were treated through volatilization of hydrocarbons. Ground-water pumping in the source area, combined with air stripping has further reduced contaminant concentrations. Replacement water supplies are being installed while remediation continues. A ground-water model has been developed which is being used to predict the effect of remedies. A decision on the final remedy for this site will be made in 1996.