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Wenck August 18, 2011 Rebecca Haug Environmental Administrator City of Elk River 13065 Orono Parkway Elk River, MN 55330 RE: Response to Comments received at August 4, 2011 meeting: Land Use Application for 27.2 Acre Southern Expansion Elk River Landfill Dear Ms. Haug: Wenck Associates, Inc. 1800 Pioneer Creek Center P.O. Box 249 Maple Plain, MN 55359-0249 (763) 479-4200 Fax (763) 479-4242 E-mail: wenckmp@wenck.com AUG 1 9 2011 On behalf of Waste Management, it-was our pleasure to meet with you on August 4, 2011 to discuss the remaining comments on our Land Use Application that is on the agenda for approval at the City Council meeting scheduled for September 19, 2011. As discussed below are the responses to the nine items that were the topic of our discussion on the August 4, 2011 meeting. As you indicated the following nine items as they relate to policy and technical issues are: Technical Issues: 1. Additional storage capacity for Pond P-2 can be obtained by resetting the outlet elevation from 1021 to 1025. Similarly, the outlet for Pond P-1 should be reset from elevation 993 to 995, with a corresponding adjustment in the elevation for the south inlet pipe from the west downslope structure. Response: ERL has designed the sedimentation basins as a part of the site storm water management network to handle a designed storm event, control discharge rates, and minimize erosion. Capacity of the ponds must include storm retention capacity as well as "free-board" capacity to control discharge rates that will minimize erosion. Outlet elevations are defined as a part of the design process and cannot be changed without consideration for the design. Changing the elevations of the discharges increases the permanent holding capacity of the pond but reduces the storage/retention capacity of the pond to handle the storm events, which is critical for the overall storm water management system. The ERL has prepared a revised and more descriptive summary of the storm water management system including a revised subwatershed map that may help to clarify the design basis for the stormwater management system. This as well as the HydroCad model runs for the 25 yr and 100 yr storm events are provided in Attachment L 2. The length of uncontrolled surface water drainage for final cover topslopes is excessive. Additional surface water control berms are needed to break up the area to prevent surface erosion. A particular concern exists for the west portion of expansion area where surface water from topslopes is designed to flow onto sideslopes. The proposed drainage downslope structures must be extended up the slope and additional routing berms placed to provide conveyance for surface water drainage collected on top slopes. These plan revisions will be necessary before Planning Commission review. T:\0742\1406Vune1 ] CityApp\Comment response\Response_081811 \LRH_0804 ] 1 MtgResponse_081811.docx