Ahtna Environmental, Inc., (Ahtna) completed a three-phase remedial pilot study to address soil and groundwater impacts resulting from a former dry-cleaning operation at U.S. Coast Guard (USCG) Base Kodiak Site 3. The site was a hazardous waste management unit (HWMU) regulated by Base Kodiak’s Resource Conservation and Recovery Act (RCRA) Permit. In Phase 1, Ahtna conducted additional site characterization to fill data gaps on the nature and extent of the contamination, and established baseline values for multiple geochemical parameters for the groundwater.
During Phase 2, Ahtna rerouted buried utilities to remove a preferential flow pathway for contaminants in groundwater to reach Inner Women’s Bay.
In Phase 3, Ahtna performed the pilot study involving the removal of soil impacted with chlorinated solvents, using a large-diameter auger and backfilling with amended soil designed to promote degradation of site contaminants. Five chlorinated compounds were previously identified as the primary compounds of concern: tetrachloroethene (PCE); trichlorethene (TCE); 1,2-dichorethene (1,2-DCE); vinyl chloride (VC); and chloroform.
Site 3 was in post-closure care and corrective action under the terms of the Base Kodiak RCRA Permit. However, a second source area discovered at the site was not being remediated by the existing treatment system. To remain in compliance with the RCRA Permit, a viable corrective action technology needed to be identified for this second source area.
The Ahtna team was able to successfully complete the excavation of highly contaminated soil up to 25 feet below the groundwater table without disturbing the foundation of a nearby building, thereby demonstrating that this corrective action method was a viable alternative for the site.
Initial groundwater sampling and analysis conducted after the soil removal and amended backfill showed a substantial drop in contaminant concentrations in the vicinity of the pilot study area. Additionally, the groundwater characteristics have changed as expected toward conditions more conducive to biodegradation of remaining contaminants. Follow-on monitoring of groundwater is planned.
U.S. Coast Guard