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19. 20. 21. 22. 23. 24. Groundwater quality at the water table in the Upper Sand aquifer in the vicinity of the Anoka Regional Sanitary Landfill has been affected by teachate percolating through the unlined bottom of the site (Remedial Investigation). The Remedial Investigation water quality monitoring program, which began in 1985, has included collection and analysis of 258 samples from groundwater monitoring wells, 64 samples from private wells, and 11 samples from surface waters. During the course of the project, over 16,000 tests have been performed on water samples for volatile organic compounds, heavy metals and other' indicator parameters (Remedial Investigation). The horizontal extent of groundwater contamination has been defined to be within an area approximately 2500 feet downgradient of the landfill boundary. Maximum total VOC concentrations are observed to be approximately 3000 ug/I 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 resampling 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. Detectable levels of VOCs at the water table are restricted to within approximately 800 feet of the landfill boundaries. Total VOC concentrations detected at the water table range from about 28 ug/l to near 1000 ug/I with the highest concentrations occurring in wells east of the landfill (MW-8, MW- 16A, MW-IAR). Aromatic and ether compounds were only detected in the area east of the landfill at the water table, while the halogenated compounds were present in all samples collected from water table wells in which VOCs were :detected. Ether compounds were present in significantly higher concentrations than the aromatic compounds and were detected within a larger area than the aromatics. The aromatic compounds are generally associated with petroleum products or paint solvents. Aromatics are Iow molecular weight, highly volatile compounds that are moderately soluble in water from an environmental chemistry definition. These compounds also possess specific gravities less than avalue of one which indicates the compounds are less dense than water.