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C-1981-022 <br />RN-05 Findings <br />February 2009 <br />3. The Sanborn Creek workings undermined portions of two abandoned mines - the <br />Oliver Mine and the Hawk's Nest Mine. The Oliver Mine was mined in the 1930's <br />and is thought to be flooded. An exposure of the workings adjacent to the old <br />county road formerly discharged water at a rate of a few gallons per minute. <br />About 90 percent of the workings of this mine lie downdip of the discharge point. <br />The Hawk's Nest Mine lies north of the Oliver Mine and is stratigraphically higher <br />than the Oliver D seam. Hawk's Nest mined in both the E and F seams. The <br />workings of this mine are probably not flooded, as indicated by measurements in <br />an old drill hole. Also, during operation of the Hawk's Nest Mine, there was very <br />little inflow. <br />Because potential exists for subsidence to cause fracturing of the interburden <br />between the B seam and the flooded workings of the Oliver Mine, Oxbow Mining, <br />LLC limited extraction in the Sanborn Creek Tracts under those areas known to be <br />flooded. <br />4. In the now-abandoned Hawk's Nest Mine several drill holes were drilled down <br />from the active mine into lower seams. It is believed that these holes are not <br />sealed and could provide a conduit for water to flow into the Sanborn Creek mine; <br />however, as reported in the PHC, there was no evidence of flooding of the mine at <br />the time of this renewal. <br />Mine inflow, except that used in the mining process, will be treated and discharged to <br />the North Fork. The discharge will meet NPDES standards, but it is expected that the <br />discharge will have an elevated TDS for which there are no discharge standards: From <br />recent water quality analyses, TDS values of 3,200 mg/1 for the discharge can be <br />expected. During the emergency mine water discharge of the Sanborn Creek Mine in <br />1999, water quality analyses of the discharge water showed TDS ranging from a low of <br />2668 mg/1 to a high of 4785 mg/l. <br />Post-mining impacts are expected to be small. The Sanborn Creek mine is expected to <br />slowly flood to the level of the river, which is below the elevation of the portal. <br />Discharge from the portal is unlikely. The water quality of the flooded workings is <br />anticipated to be the same as that of the old Somerset Mine. After mine closure, the <br />proposed Sanborn Creek area is not expected to contribute additional dissolved solids to <br />the river. <br />The Elk Creek Mine, based on data from other mines in the vicinity, should not <br />experience problems with inflow or eventual discharge from the portal. Inflows <br />experienced in the vicinity include 115 gpm in the B seam at Oxbow, 15 gpm in the C <br />seam at Oxbow, and very little water at all in the D-seam in Bowie I and II, with <br />24