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County provides feedback on cleanup plan for 3M site

Washington County is giving its two cents to the Minnesota Pollution Control Agency on a proposed cleanup plan for the 3M Cottage Grove site.

The Washington County Board of Commissioners voted Tuesday to approve a letter of feedback on the agency's proposed cleanup plan for the site that addresses contamination related to perfluorochemicals (PFCs) in wastes disposed of at the site by 3M.

For the last several months officials at the MPCA and 3M have held public meetings to inform residents in the affected area about future plans to cleanup the PFC contamination at and around the site.

The county's letter to the MPCA states the county finds the proposed plan, which includes three methods of remediation, generally consistent with county policies, but cites concerns over one of the aspects of the plan that calls for expansion of the existing groundwater extraction system.

The "Alternate GW-1," one of three cleanup methods chosen by the MPCA, includes adding treatment to the existing pump-out system at the site. The county letter to the MPCA, signed by Washington County Commissioner Myra Peterson, states the complex nature of the hydrology in the area is cause for concern.

"The proposed extraction wells are to be located near a series of faults that have been mapped by the Minnesota Geological Survey," the letter states. "The county feels that this warrants further study of how the faults may affect the pumping intended to contain the contamination.

The letter also asks the MPCA to make sure that the existing pump-out system at the 3M site will remain online throughout the clean-up process to prevent contaminants from migrating off-site.

The proposed cleanup plan of the 3M Cottage Grove site is the result of a 2007 settlement agreement between the MPCA and 3M that established a consent order for 3M to remediate three PFC disposal sites (Oakdale, Woodbury and Cottage Grove).

As a part of the agreement, 3M completed an investigation and study which identified any remaining risks to public health or the environment from the releases of PFCs at the site.

Over the last two years, 3M has developed a list of cleanup alternatives that the MPCA has monitored.

The public has been allowed to comment on the cleanup plan through June 19. After the MPCA adopts a final remedy for the site, 3M will prepare construction design documents for MPCA review and approval.