Contaminated groundwater plume near Victor shrinking

Some restrictions on shallow well use may be lifted

The Montana Department of Environmental Quality (DEQ) has issued an Amendment to the Record of Decision (ROD) for the Bitterroot Valley Sanitary Landfill State Superfund Facility (facility). This amendment will make some changes original to the original 2002 ROD for the facility.

The landfill started on about 30 acres of land located south of Victor where the Bitterroot Disposal Transfer Station currently operates. 

In 1985 the Department of Environmental Quality conducted a preliminary assessment of the groundwater in the area and discovered contamination. At least some of the primary contaminant, Chloroform, may have originated from chemical laboratory waste being dumped at the site by Ribi Immunochem. The plume was traced from the dump site located on the west side of Highway 93 to the river located east of the highway.

The National Institutes of Health began cleanup operations in 1994. A pump and groundwater treatment system were installed at the time and operated until 2012, when it was discovered that the plume had undergone significant reduction in size.  NIH initially provided bottled water for landowners in the area affected by the plume. Later they drilled deep source wells that reached below the contamination to provide water to impacted landowners.

The new amendment to the original 2002 ROD went through a public review process conducted by DEQ in 2018. It changes the original decision in a number of ways.   The portion of the final remedy requiring a community water supply system was found to no longer be necessary, so DEQ is removing this requirement.

Since the size of the groundwater plume where contamination exceeds site specific cleanup levels (SSCLs) has greatly reduced, DEQ will work with the Department of Natural Resources and Conservation (DNRC) to reduce the size of the Controlled Groundwater Area (CGWA) installed at the Facility as part of the remedy. 

According to Environmental Science Specialist Matthew Kent, once the CGWA is modified, residents may return to domestic water use from wells in the shallow aquifers. DEQ is revising the SSCLs for groundwater to incorporate revised water quality standards and establishing SSCLs for chloroform for vapor intrusion.

The agency is maintaining the existing institutional controls in the form of restrictive covenants that prohibit development on the former landfill property to mitigate any potential risk posed by vapor intrusion.

Copies of the ROD Amendment and other site-related documents are available at Farmers State Bank, 103 Main Street, Victor, Montana; the Bitterroot Public Library, 306 State Street, Hamilton, Montana; and the DEQ State Superfund Unit of the Waste Management and Remediation Division office located at 1225 Cedar Street in Helena.

Later in 2022, DEQ plans to contact residents who still use deep replacement wells installed before the original ROD was issued to discuss options to continue to meet their domestic water needs going forward. Anyone with questions regarding the ROD Amendment may contact Matthew Kent at mkent@mLgov or 406-444-6479.