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<br />As described above, relatively continuous sandstones in the lower <br />Burro Canyon Formation yield small amounts of water to wells and <br />are the source of several small springs and seeps in and around the <br />permit area. Along with the rest of the stratigraphic section, this <br />formation dips to the north at 2 to 3 degrees in the area. <br />Discharge to the surface occurs at the seeps mentioned above. The <br />formation does not outcrop within the permit area. Recharge to the <br />Burro Canyon likely occurs well south of the permit area, and <br />perhaps across bedding planes from adjacent finer-grained shales of <br />the Burro Canyon and Morrison Formations. Approximately 90 to 100 <br />feet of interbedded shale, coal, and sandstone lenses separate the <br />aquifer from the floor of the proposed mining pit, and there is no <br />evidence that the aquifer is under sufficient head to cause leakage <br />from the aquifer into the pit. <br />As the Burro Canyon has insufficient head to cause upward migration <br />of water, no loss of water is anticipated. Some infiltration of <br />precipitation into the pit floor is likely, and by way of fractures <br />some of this water could reach the Burro Canyon aquifer. However, <br />infiltration would occur in such limited quantities that any water <br />quality impacts would be limited to the immediate permit area. <br />Sedimentary rocks of the Dakota Sandstone in the permit area, which <br />will be exposed in the pit walls, probably do not contain <br />measureable amounts of water, as none has been encountered in <br />monitoring wells. Isolated lenses of perched water could be <br />encountered by the pit, however they will not be sufficient to <br />present either an operational or an environmental problem. <br />Impacts to alluvial aquifers could occur in two ways, the <br />diminution of recharge by detention of water in sediment ponds, and <br />contamination by discharges from spoil springs. The relatively <br />small maximum disturbed area of 257 acres will limit spoil spring <br />development and pond water retention. Therefore, associated <br />impacts should be minimal. <br />Detention of runoff in the ponds will be minor, as the disturbed <br />areas make up very small percentages of the watersheds in <br />question. Therefore, alluvial impacts due to retention of recharge <br />water should be negligible. <br />The permit application states that spoil springs should not develop <br />due to the low precipitation in the area (approximately 12 inches <br />per year). Assuming 2 inches of infiltration per year (d <br />conservative estimate based on 3 inches of infiltration reported at <br />the Seneca II Mine in Routt County, which receives more <br />precipitation than the Hamilton Mine area), approximately 43 <br />acre-feet of water per year of recharge to the spoil aquifer would <br />occur. If the aquifer reaches a steady state which includes <br />discharge from springs at the topographically lowest points of the <br />pit walls, this amount of recharge would translate into an average <br />spoil spring discharge of 26.6 GPM (0.06 CFS) for all sources <br />within the permit area. It is likely that spoil spring development <br />-16- <br />