Resolution - #91-04-088 - 04/23/1991

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28. 30. 31. 32. 33. Limited inorganic water quality data are available for private wells. From the available water quality data, it appears that the private wells sampled, whether bedrock, lower sand, or unknown screened position, are free of any impact from landfill operations (Remedial Investigation). Currently, no public health hazard exists and that limited potential exists for the ..~ccurrence of future hazards to public health. The results of the investigation have also indicated that site conditions are such that, through the application of available technology, water quality impacts in the vicinity of the Anoka Regional Sanitary Landfill can be effectively managed (Remedial Investigation). Five surface water bodies located near the landfill have been sampled. These include an upgradient pond near well nest MW-6 (SW-1), an upgradient wetland near well nest MW-15 (SW-2), a downgradient wetland near well MW-20B (SW-3), a downgradient wetland location near well MW-35BB (SW-5); and Sunfish Lake east of well nest (MW-18 (SW-4). No adverse water quality impacts have been detected in the surface water bodies (Remedial Investigation). The remedial objective is to reduce the concentrations of total VOCs, 1,2-dichloroethane, tetrachloroethylene, nickel, and zinc in the unconsolidated aquifer downgradient of the landfill. These parameters were selected, with the concurrence of MPCA, as indicator parameters, and are representative of the contaminants that will be encountered in the plume. The premise for this plan is that control of key selected-parameters will assure control of other parameters as well (RAP - February, 1990). Modeling predictions by Principia Mathematica, inc. indicate that operation of 12 flow barrier wells pumping at 25 gallons per minute (gpm) and the operation of eight groundwater recovery wells pumping at 100 gpm, will clean up the downgradient aquifer within approximately ten years. Predictions also show that contamination will only marginally enter the Bedrock High zone. It is assumed that well operation will begin on July 1, 1991 (RAP - February, 1990). During the initial ten years of pumping when both flow barrier and groundwater recovery wells are operating, groundwater drawdown beneath Sunfish Lake is predicted to be between 1.5 and 4.5 feet. Afterwards, when only the flow barrier wells are operating, the drawdown beneath Sunfish Lake is predicted to be between 0.5 and 1.0 foot. In order to maintain the average elevation in the lake under both pumping situations, 11.4 and 2.8 gpm of replacement water would be required, respectively (RAP - February, 1990).