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Dustin Czapla <br />Loesch Pit, M-1981-068, Garfield County, CO. <br />Technical Revision - Pit wall liner <br />Page 6 of 7 <br />Oct. 4, 2010 <br />piped overflow on the west side of the pit. If the pit is used to store water, the water level will <br />be controlled by the gated overflow on the west side of the pit. <br />Slope Stability The worst case scenario for slope stability is the operating conditions, e.g., <br />current conditions. Current conditions are such that where the liner has been placed, <br />hydrostatic head can build up on the outside of the liner. To keep the liner in place, it must be <br />restrained by surcharge, which is the topsoil placed on top of the liner. Assuming the pond is <br />filled, the post reclamation conditions will have water on both sides of the liner, which will <br />reduce the net hydrostatic force pushing on the liner. When the water level in the pit and the <br />water level outside of the lined wall are at the same elevation, there will be no net hydrostatic <br />force against the liner. Under saturated conditions the loamy topsoils should typically be <br />stable and not prone to slumping with final constructed slopes of 4H:1 V or flatter. Typically <br />saturated soils are most prone to slumping during rapid drawdown conditions. Such <br />conditions are not likely during post-reclamation conditions, as there is no mechanism <br />available to rapidly draw down the ponds, e.g., a drawdown rate of greater than approximately <br />one foot per day. Such drawdown rates are highly unlikely, as the ponds are not a source of <br />water supply other than for storage of augmentation water for evaporative losses from the <br />surface area of the ponds, as well as possibly as a source of irrigation water. <br />WATER IESOURCE CONSULTANTS, LLC <br />mm"