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As the Burro Canyon has insufficient head to cause upward migration of water, no <br />loss of water is anticipated. Some infiltration of precipitation into the pit floor is <br />likely, and by way of fractures some of this water could reach the Burro Canyon <br />aquifer. However, 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 will be <br />exposed in the pit walls, probably do not contain measurable amounts of water, as <br />none has been encountered in monitoring wells. Isolated lenses of perched water <br />could be encountered by the pit, however, they will not be sufficient to present <br />either an operational or an environmental problem. <br />Impacts to alluvial aquifers could occur in two ways, the diminution of recharge by <br />detention of water in sediment ponds, and contamination by discharges from spoil <br />springs. The relatively small maximum disturbed area of 257 acres will limit spoil <br />spring development and pond water retention. Therefore, associated impacts should <br />be minimal. <br />Detention of runoff in the ponds will be minor, as the disturbed areas make up very <br />small percentages of the watersheds in question. Therefore, alluvial impacts due to <br />retention of recharge water should be negligible. <br />The permit application states that spoil springs should not develop due to the low <br />precipitation in the area (approximately 12 inches per year). Assuming 2 inches of <br />infiltration per year (a conservative estimate based on 3 inches of infiltration <br />reported at the Seneca II Mine in Routt County, which receives more precipitation <br />than the Hamilton Mine area), approximately 43 acre-feet of water per year of <br />recharge to the spoil aquifer would occur. If the aquifer reaches a steady state which <br />includes discharge from springs at the topographically lowest points of the pit walls, <br />this amount of recharge would translate into an average spoil spring discharge of <br />26.6 GPM (0.06 CFS) for all sources within the permit area. It is likely that spoil <br />spring development will be considerably less than this prediction, due to the limited <br />amount of contributing rainfall. The applicant projects there will be no spoil <br />discharge. Any spoil spring discharge would be of relatively poor quality, perhaps 2 <br />to 3 times higher in Total Dissolved Solids than background water quality, but <br />would be easily diluted to background quality prior to any use downstream. <br />When ground and surface monitoring resume, the applicant will conduct an annual <br />spoil spring survey that will presumably support these projections. Any springs with <br />discharge of at least 10 GPM will be identified and sampled for a full suite of <br />parameters, with a report to be submitted to the Division by June 15 of each year. <br />The applicant has also committed to replacement of any adjudicated source of water <br />that may be impacted by the proposed mining operation, as would be required by <br />Colorado water law. <br />14