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Dames ~ Moore <br />• Flatiron Companies <br />May 17, 1982 <br />Page 4 <br />The quality of the surface water which may discharge from the East Dump <br />may be chemically degraded to a minor degree due to the leaching of the dump <br />material by precipitation and runoff. <br />The methods utilized for dump placement, sediment collection during <br />placement and stabilization with erosion control following placement are <br />expected to result in minimal release of sediment from the East Dump down- <br />stream in Mann Draw. <br />Any degradation of surface water quality in Mann Draw due to possible <br />leaching of the East Dump materials is unlikely to cause a measurable change <br />in the water quality of the Canadian River downstream from its confluence with <br />Mann Draw. <br />• Due to the infrequency of channel discharge in Mann Draw, there are no <br />regular users of surface water from this drainage course. The annual volume <br />of surface runoff from Mann Draw to the Canadian River is not expected to <br />change significantly as a result of drainage modifications caused by placement <br />of the East Dump. <br />Ground Water <br />Due to the expected higher permeability of the East Dump materials <br />compared with the Pierre Shale originally exposed in this area, and because of <br />the flatter slopes created by dump placement, the rates of snowmelt and <br />rainfall infiltration should increase with resulting increases in ground-water <br />recharge. <br />Some slight degradation of downgradient ground-water quality is the near <br />vicinity of the mine may occur as the dump materials are leached by subsurface <br />infiltration. Based on monitoring results to date, ground-water quality <br />• <br />