5.4. SR 05-17-2010 - Laserfiche WebLink

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Explanation of Request Y'ermit rVlodification The Elk River Landfill, Ina. (ERL) is permitted by the 1dIPCA and also has a City of Elk River License and Conditional Use Permit. We have submitted a permit modification request, which improves the design of the facility and provides for a more efficient leachate collection system and more efficient use of the designated landfill footprint. Detailed information can be found in the permit modification engineering report and plans. In general the major design improvements include the conversion from gravity leachate collection lines which drained to the leachate storage tank, to leachate lines which drain to an internal sump pump from which leachate is pumped to storage tanks via a force main. The improved design does not include an increase in footprints, nor does it include an increase in the ultimate capacity of the facility. The design now incorporates an earth berm along the western and southern portion of the landfill footprint. The berm allows far more efficient use of landfill airspace and also allows for an increased visual screen along the western and southern sides of the facility. Because of the footprint required for the berm, the number of landfill cells decreases from 18 to 17. The modified design also changes the final cover slope from S:1's to 3:1's and includes the use of "benches" in the final contour plan and the use of a geonet drainage layer in the final cover system. The benched final contour plan is very similar to a farm field terrace system concept, which is often used to minimize erosion. The benches provide a break in surface water flow and also offer excellent access to the upper portions ofthe landfill. During review of the 3:1 slopes and the cover components, detailed engineering analysis, including slope stability review, surface water control and erosion control, was completed. Three to one slopes are successfully used at other landfill facilities across the nation. Please refer attached plan sheets for detailed information. Leachate xecirct~lation The second project under consideration is leachate recirculation. Currently leachate from the facility is trucked over 60 miles to the wastewater treatment plant in St. Paul. The leachate recirculation project proposes to treat leachate on-site through a series of perforated pipes laid in trenches at 30-foot height intervals within the active landfill cell. Leachate will be force mained into the pipes at timed intervals and allowed to saturate the