Resolution - #97-05-136 - 05/27/1997

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11. 12. 13. 14. 15. 16. 17. 18. A Feasibility Study - Detailed Analysis Report was prepared by Foth & VanDyke and Associates, Inc. on behalf of Waste Management of Minnesota, Inc. (WMMI) for the Anoka Regional Sanitary Landfill, in accordance with a consent order entered into with the Minnesota Pollution Control Agency on May 30, 1985. The Consent Order required that a Remedial Investigation (RI), Feasibility Study (FS) and possible Response Actions be undertaken at the Anoka site. The purpose of these steps is to determine if a release or threatened release of hazardous substances exists at the Anoka site, and to develop and implement remediation strategies, if necessary. An exposure risk assessment prepared for the "No Action" alternative in the Detailed Analysis Report concluded that if remediation were not undertaken, an unacceptable human health risk would exist form the ingestion of groundwater containing vinyl chloride and 1,2,-dichlorethane, and from the inhalation of vapors containing these two compounds. Therefore, the study proceeded with an evaluation of potential remedial alternative components. Work under the Remedial Investigation was completed in conformance with a Consent Order, an approved work plan, work plan addendums and MPCA approved Quality Assurance/Quality Control plans. Available records indicate that the majority of waste deposited in the landfill is mixed municipal refuse. During the initial period of site operation, a limited amount of what is currently classified as hazardous waste is believed to have been co-disposed with mixed municipal refuse (Remedial Investigation). Groundwater quality at the water table in the Upper Sand aquifer in the vicinity of the Anoka Regional Sanitary Landfill has been affected by leachate percolating through the unlined bottom of the site (Remedial Investigation). That the applicant has been regularly performing assessment monitoring to determine the effectiveness of the groundwater pump-out treatment system since 1991. Based on the groundwater monitoring data collected, to date, the pump-out system is performing as predicted. The horizontal extent of groundwater contamination has been defined to be within an area approximately 2,500 feet downgradient of the landfill boundary. Maximum total VOC concentrations are observed to be approximately 3,000 ug/1 in one area of the Tunnel Valley aquifer near the landfill. Water quality impacts to the underlying bedrock aquifer have not been detected (Remedial Investigation). The private wells sampled near the landfill have been shown not to be impacted by VOCs. VOCs attributable to groundwater quality impacts have been confirmed to be not present in the private supplies. VOCs have been detected sporadically at private wells but their presence was not confirmed upon re-sampling and/or are likely to be associated with laboratory analytical procedures. The findings have been verified with split samples analyzed by the Minnesota Department of Health. RESOLUTION #97-05-136 Page 3 of 6