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_2P_ <br />permit and adjacent areas. The only regional aquifers which will be affected <br />by degraded spoil water are the Sudduth coal seam and the Upper Sandstone <br />member of the Pierre Shale. Both of these aquifers have low permeabilities <br />and the migration of ground water high in TUS from the spoil aquifer will be <br />extremely slow. Movement of ground water within these aquifers will be down <br />the dip of the strata toward the axis of the Bourg Syncline. Due to the lower <br />infiltration rate, very low precipitation rate (i.e., 11 inches/year), the <br />increased storage capacity of the spoil aquifer, and the absence of springs or <br />seeps from coal or the sandstone memoer in the permit and adjacent areas. The <br />degradation of surface waters from spoil water seeps or springs is not <br />anticipated. <br />To date, the Bourg Strip Mine has experienced no regular ground water inflows <br />into the pit. A small amount of localized water was encountered below the <br />level of the Mann Draw alluvium beside a fault. <br />Cumulative Hydrologic Impacts Study <br />Effects on Surface Waters <br />The Bourg Strip Mine, the I~larr Strip and the Canadian Strip are all located on <br />the southwestern half of the Canadian River Watershed. As such, their <br />combined mining activities will impacts to some degree the quality and <br />quantity of surface waters in the Canadian River. In addition, the lNarr and <br />Canadian Strips will cumulatively impact the quality and quantity of surface <br />water in Bolton Uraw. <br />The three mines within the North Park Coal Field will cumulatively impact the <br />quantity and quality of surface water in three ways. These include; 1) <br />changes in runoff and erosion rates; 2) increases in salt loads to the <br />Canadian River and its tributaries; and 3) changes in the ionic balance of <br />surface waters. The following discussion is a worst case scenario which <br />assumes all mining occurs at the same time. <br />Runoff and Erosion <br />During mining, disturbed areas will be susceptible to erosion and <br />runoff. This is mitigated by respective sediment control systems. <br />Sediment control cannot be removed until revegetation is successful and <br />erosion rates drop to natural levels. <br />While the sediment ponds are present, they will reduce runoff to the <br />receiving streams to the following extent: <br />Receiving Stream <br />Bolton Draw <br />Bush Draw <br />Williams Draw <br />Sudduth Draw <br />Mann Draw <br />Canadian River <br />Percent Detention <br />1 B. 9% <br />5.4% <br />17.4% <br />2.9% <br />4. U% <br />0.32% <br />