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16. <br /> <br />An exposure risk assessment prepared for the "No Action" alternative in the <br />Detailed Analysis Report concluded that if remediation were not undertaken, an <br />unacceptable human health risk would exist from the ingestion of groundwater <br />containing vinyl chloride and 1,2,-dichlorethane, and from the inhalation of <br />vapors containing these two compounds. Therefore, the study proceeded with <br />an evaluation of potential remedial alternative components. <br /> <br />17. <br /> <br />Work under the Remedial Investigation was completed in conformance with a <br />Consent Order, an approved work plan, work plan addendums and MPCA <br />approved Quality Assurance/Quality Control plans. <br /> <br />18. <br /> <br />Available records indicate that the majority of waste deposited in the landfill is <br />mixed municipal refuse. During the initial period of site operation, a limited <br />amount of what is currently classified as hazardous waste is believed to have <br />been co-disposed with mixed municipal refuse (Remedial Investigation). <br /> <br />19. <br /> <br />Groundwater quality at the water table in the Upper Sand aquifer in the vicinity <br />of the Anoka Regional Sanitary Landfill has been affected by leachate <br />percolating through the unlined bottom of the site (Remedial Investigation). <br /> <br />20. <br /> <br />The Remedial Investigation water quality monitoring program; which began in <br />1985, has included collection and analysis of 258 samples from groundwater <br />monitoring wells, 64 samples from private wells, and 11 samples from surface <br />waters. During the course of the project, over 16,000 tests have been <br />performed on water samples for volatile organic compounds, heavy metals and <br />other indicator parameters (Remedial Investigation). <br /> <br />21. <br /> <br />The horizontal extent of groundwater contamination has been defined to be <br />within an area approximately 2500 feet downgradient of the landfill boundary. <br />Maximum total VOC concentrations are observed to be approximately 3000 <br />ug/I in one area of the Tunnel Valley aquifer near the Landfill. Water quality <br />impacts to the underlying bedrock aquifer have not been detected (Remedial <br />Investigation). <br /> <br />22. <br /> <br />The private wells sampled near the landfill have been shown not to be impacted <br />by VOCs. VOCs attributable to groundwater quality impacts have been <br />confirmed to be not present in the private supplies. VOCs have been detected <br />sporadically at private wells but their presence was not confirmed upon <br />resampling and/or are likely to be associated with laboratory analytical <br />procedures. The findings have been verified with split samples analyzed by the <br />Minnesota Department of Health. <br /> <br /> <br />