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December 10, 2010 <br />Groundwater Area of Concern (GWAOC) <br />The GWAOC is defined as the area of land surrounding a landfill where the <br />presence of activities that require the use of groundwater may be impacted or <br />precluded by contamination from the landfill, or may cause the groundwater flow <br />direction to change thereby impacting the user or others nearby. The GWAOC is <br />used to inform the public about the current and potential risks to users of <br />groundwater contaminated by the landfill. In most circumstances this area is not <br />equidistant around the site. Minnesota Department of Health (MDH) statutes <br />establish the minimum installation distance for a water- supply well from mixed <br />municipal solid waste at 300 feet, and 600 feet where the well is not constructed <br />through a confining layer such as clay or shale. <br />Groundwater Area of Concern around Anoka /Ramsey Landfill <br />The groundwater area of concern around Anoka /Ramsey Landfill is defined by an <br />environmental monitoring system that consists of approximately 104 wells. The <br />groundwater contamination is in the Upper Sand that is part of the Anoka sand <br />plain aquifer. There is also groundwater contamination in a glacial channel where <br />the Grantsburg Till (that lies below the Upper Sand) is eroded and the Upper and <br />Lower Sand are connected. Contaminants in groundwater that exceed drinking <br />water standards include vinyl chloride, 1, dichloroethane and manganese. <br />The groundwater plume is shown in two dimensions but extends to a depth of <br />100 feet below the ground surface. The area of concern extends east 1 066 feet <br />beyond the plume boundary to include parcels that are not on city water because <br />there may be shallow ground water flow towards Sunfish Lake. The area of <br />concern extends to the southeast 1,614 feet beyond the plume boundary <br />because there are parcels in this direction that are not on municipal water and <br />regional flow in the shallow groundwater is to the southeast. Private wells to the <br />east and southeast are protected by the Anoka Municipal Regional Landfill <br />groundwater extraction system and by the geology of the bedrock aquifer. In <br />addition, flow in the bedrock aquifer is to the south and southwest from the waste <br />footprint. These wells will be periodically sampled to verify that the Tunnel City <br />Group bedrock aquifer is still contaminant free. <br />