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-4- <br />Carbon ditch. Mine water is expected to have a degraded water quality <br />(see example analysis, Figure 2.04.7(2)(b)-2, Sample 2) and would be <br />expected to affect water quality in Ward Creek. The average water <br />quality observed in the sediment pond has a total dissolved solids <br />concentration of 1617 mg/1 and an SAR of 18.96. When water of this <br />quality is added at the rate of 0.17 cfs to flow in Carbon Ditch, the <br />resulting flow has a TDS of 340 mg/1 and an SAR of 2.79. Such water is <br />suitable for irrigation with a medium salinity hazard and a low sodium <br />hazard. Similar calculations for Ward Creek at low flow result in a <br />predicated TDS of 303 mg/l, and an SAR of 0.85. This water is also <br />suitable for irrigation, with a medium salinity hazard and a low sodium <br />hazard. Both the Carbon Ditch, and Ward Creek currently have waters with <br />low sodium hazard and low salinity hazards. <br />After the cessation of mining operations, mine water would no longer be <br />pumped from the underground workings. As a result, the mine workings <br />would eventually fill with water, and the natural flow pattern would be <br />restored. Ground water passing through the abandoned workings would <br />eventually discharge to the glacial/alluvial aquifer. Water passing <br />through the mine workings would be expected to have a degraded water <br />quality. Water found in adjacent old mine workings is degraded (TDS, <br />10,509 mg/1, and SAR, 27). If water of this quality discharged to the <br />stream/alluvial aquifer system at the same rate as maximum ground water <br />inflow to the mine workings, the resulting water quality in the stream <br />under low flow conditions would be a TDS concentration of 698 mg/1, and <br />an SAR of 4. Water of this quality has a moderate salinity hazard and a <br />low sodium hazard. It is suitable for irrigation, but slightly higher <br />application rates might be necessary. <br />Other possible effects not discussed by the applicant would not be <br />expected to be significant. Increased runoff and erosion from the <br />surface disturbances associated with the mine would be routed to a <br />sediment pond. Water released from the pond would have low sediment <br />concentrations and in some instances might be erosive. In this case, <br />however, surface flows are infrequent and the amount of water to be <br />released on a continuous basis is small (less than 0.17 cfs) and should <br />not cause significant downstream erosion. The pond contains 1.24 <br />acre -f t. ~ dead storage, but this would normally be filled with water <br />from the underground workings so the pond would not decrease surface flow <br />from the site. <br />Alternative Water Supplies and Protection of the Hydrologic Balance <br />The proposed mining operation would undermine the stream/alluvial aquifer <br />system which is a significant local water resource. Although the <br />applicant's discussion for probable hydrologic consequences indicates <br />that significant hydrologic effects are not expected, the potential for <br />