2009-02-09_GENERAL DOCUMENTS - C1981022 (3)

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