February 7, 1996
American Dental, at 2801 Reserve Street in Missoula, is an inactive, approximately 1½-acre dental plating facility which operated from 1974 to 1991. In the early and mid-1970s, facility operators improperly disposed of waste solvents in the parking lot. Waste material, including trichloroethylene, Stoddard solvent and plating wastes, were also placed in an on-site sump. In 1983 and again in 1993, water pipe leaks resulted in the sump and/or plating area filling with water, some of which apparently seeped into the underlying groundwater.
The site is located in a primarily commercial area on Missoula's southwest side. It is underlain by Missoula's sole source aquifer.
A December 1992 CERCLA preliminary assessment by MDHES described on-site soils contamination with metals, chlorinated solvents and petroleum hydrocarbons and noted that groundwater contamination was suspected but not verified.
An October 1993 CERCLA site investigation by MDHES consultants indicated very high concentrations of cyanide and metals in soils underneath the plating tank, elevated solvents and metals in a dry well, and elevated nickel and chromium levels in the groundwater.
In August 1994, the current site owner conducted a voluntary remedial action with MDHES oversight. The site owner's contractor demolished the plating building, excavated contaminated soil and properly disposed of it, backfilled the area with clean soil, installed a soil vapor extraction (SVE) system to remove volatiles and began quarterly groundwater monitoring. The area is now a paved parking lot.
In October 1995, the Montana Department of Environmental Quality (MDEQ; formerly MDHES) CECRA program determined the SVE system had successfully remediated the site. Groundwater monitoring showed no significant remaining contamination. MDEQ-CECRA declared the site "No Further Action" under CECRA.