Agenda - Council - 09/13/1982 - Special

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I I I I I I I I I I I I I I I :1 I I I Groundwater is encountered withi~ the sandy mantle. Soil borings taken in 1981 recorded groundwater at depths ranging between 9.5 and 24.5 feet. Figure 5 shows groundwater contours for the surficial aquifer. The surficial groundwater beneath the site is believed to flow to the Southeast and discharges into the Mississippi and Rum Rivers. The site is about one and a half miles from the Mississippi and slightly over a mile from the Rum. The county's report indicates that well logs for the area tend to show that static groundwater levels in the bedrock are about the same as static levels in the surficial aquifer. Data is incomplete for a conclusive finding but indi- cates little potential for vertical seepage from the surficial aquifer through the till to the underlying bedrock. lqPCA's review of the site noted that the sandy soil "allows very rapid perco- lation to the water table and provides little if any leachate attenuation."* Also, those soils do not satisfy Council criteria for soil type suitable for landfills. In recognition of the limiting hydrologic characteristics of the Anoka sand plain, Anoka County's adopted policy is to require both a liner and leachate collection system for new landfills. In order to provide added protection for any shallow water wells located between the site and discharge zone, the county has proposed that additional safeguards be provided at the Ramsey site. Figure 6 illustrates the county's proposal--in essence a system of double liners and dual leachate collection systems. The MPCA has certified the site as intrinsically suitable under the condition that the county's development proposal be implemented. The MPCA findings also noted that groundwater can be monitored by routine methods. The county has additional studies in progress to evaluate means of further reducing risks associated with the site by shortening the period in which high levels of pollutants are generated. The county is studying the effects of waste shredding on leachate production and methane gas generation. Council landfill siting criteria specify that there should be no connection between the site and either a surficial or buried drift aquifer. Site review criteria further state that by location, design and operation, waste facilities shall minimize potential public health risks and groundwater contamination. The Ramsey site by location provides no inherent protection of the surficial aquifer. There is limited protection for the drift aquifer by its artesian character and the relatively impermeable"nature of the till. The lower aqui- fers are protected to some degree by the overlying till and the St. Lawrence formation. MPCA's review also concluded that it was unlikely that the site would impact bedrock aquifers. With respect to design and operation, the county's proposal has been developed to protect the surficial groundwater and to shorten the period when risk of contamination is great. The southwestern portion of the 'site includes a marshy area that is connected hydrogeologically and by two culverts to a larger wetland south of the site. The Department of Natural Resources (DNR) wetlands inventory for Anoka County classifies this entire wetland complex as a Type III protected wetland. Council criteria specify that in order to protect environmentally sensitive areas,.landfills should not be located on or near wetlands. Anoka County should modify its development proposal for the site to ensure that this wetland is within the buffer, not the proposed fill area~ This wetland complex is connected by surface drainage to wetlands northwest of the site. Together *MPGA, R__~port on the Director's Proposed Recomendations~ 1981, p. 18.