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observed in Ward Creek by the ditch rider was 2.5 cfs in <br />1977. Therefore, the total mine inflow (and worst-case <br />streamflow depletion) represents only 7 percent of the lowest <br />streamflow observed in Ward Creek. The predicted mine inflow <br />is only about 2 percent of the average flow in Ward Creek. <br />During operations, most of the mine water was returned to the <br />Ward Creek drainage system. Mine water was pumped to a <br />sediment pond, where water not lost to evaporation was <br />discharged to the Ward Creek system via Carbon Ditch. Mine <br />water had a degraded water quality with an average <br />conductivity of 3.5 mmhos/cm and was expected to affect water <br />quality in Ward Creek. Average total dissolved solids (TDS) <br />levels in Ward Creek increased from 99 mg/1 to 194 mg/1. <br />Since the cessation of mining operations, mine water is no <br />longer being pumped from the underground workings. As a <br />result, the mine workings would eventually fill with water, <br />and the natural flow pattern would be restored. Groundwater <br />passing through the abandoned workings would eventually <br />discharge to the glacial/alluvial aquifer. Water passing <br />through the mine workings would be expected to have a <br />degraded water quality. Water found in adjacent old mine <br />workings is degraded (TDS, 10,509 mg/1, and SAR, 27). If <br />water of this quality discharged to the stream/alluvial <br />aquifer system at the same rate as maximum groundwater inflow <br />to the mine workings, the resulting water quality in the <br />stream under low flow conditions would be a TDS concentration <br />of 698 mg/1, and an SAR of 4. Water of this quality has a <br />moderate salinity hazard and a low sodium hazard. It is <br />suitable for irrigation. <br />Other possible effects would not be expected to be <br />significant. Increased runoff and erosion from the surface <br />disturbances associated with the mine would be routed to a <br />sediment pond. Water released from the pond would have low <br />sediment concentrations, but in some instances might be <br />erosive. In this case, however, surface flows are infrequent <br />and the amount of water to be released on a continuous basis <br />ie small (less than 0.17 cfs) and should not cause signifi- <br />cant downstream erosion. The pond contains 1.24 acre-feet of <br />dead storage, but this would normally be filled with water <br />from the underground workings so the pond would not decrease <br />surface flow from the site. <br />Summary and Findings <br />The Division has examined the probable hydrologic consequences <br />due to mining operations for the groundwater and surface water <br />systems at the Red Canyon Mine. The Division finds that <br />underground mining at the Red Canyon Mine will not have a <br />significant impact on these water systems. The mine will take <br />the necessary measures to ensure that mining will not affect the <br />hydrologic regime (2.07.6(2)(c)). <br />IV. Topsoil <br />No topsoil was salvaged during construction of the mine due to the fact <br />the majority of the disturbance took place before topsoil salvage was a <br />requirement under Colorado law. However, overburden materials shall be <br />used as replacement for a topsoil medium. The resulting plant growth <br />medium is the beet available at the site. This determination is based on <br />physical and chemical analyses approved by the Division (4 .06.2(4)(a)). <br />18 <br />