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A degasification borehole is located approximately 225 feet west of the electric borehole site in <br />Sylvester Gulch. It was constructed during the summer of 1997. The purpose of the <br />degasification hole is to vent mine gases to the outside atmosphere. A vacuum pump placed next <br />to the hole pumps gases out of the mine and through surface piping to move the gas up and away <br />from the site. A small metal building was constructed to house the degas pump, as well as an air <br />compressor. An as-built description is provided in Exhibit 68. <br />Sylvester Gulch: MCC has designed mine dewatering and treatment facilities to be located <br />within the Sylvester Gulch drainage. The treatment facility will provide a method of reducing <br />total suspended solids (TSS) from the mine water, if necessary, and the mine water will be <br />discharged to the West Fork of Sylvester Gulch in compliance with NPDES discharge permit <br />requirements. <br />MCC drilled one 18-inch cased borehole, one 16-inch borehole (completed as a 12-inch cased <br />hole), and two 20-inch cased boreholes during the summer of 1997 to access the operational <br />sump in the northeast comer of the.lONE Tailgate. Following the completion of ventilation seals <br />on the lONE and 11NE longwal] panels, this area will become the NE Panels Sealed sump. <br />MCC will utilize the sealed sump as a large volume mine water storage area and will pump the <br />water out of the mine through the boreholes for treatment (if necessary) and discharge to <br />Sylvester Gulch. The smaller borehole will serve as a recirculation loop to the sump and the two <br />20-inch cased boreholes will serve as alternate recirculation boreholes andlor boreholes for water <br />level indicators. Refer to the Probable Hydrologic Consequences section of the permit for <br />additional discussion of the sumps. <br />The treatment facilities will include a dewatering pump station and treatment building, <br />presedimentation basin, decant return basin and pump station, sludge drying lagoons, and <br />finishing pond. A detailed discussion of each facility is provided in Exhibit 69, Sylvester Gulch <br />Facilities Area. <br />Given MCC's experience to date (October 1998) with the good quality mine water dischazges <br />from the NW Panels Sealed sump through the Lone Pine Gulch Pipeline, MCC has indefinitely <br />postponed the construction of the treatment components of the above described facilities. MCC <br />has constructed only the pumping components in a building and the fmishing pond. However, <br />dependent on the actual quality of water pumped from the NE Panels Sealed sump, MCC may <br />build the treatment facilities in the future. <br />Lone Pine: MCC has proposed, butindefuvtely postponed the construction of a pond that would <br />be utilized exclusively to contain and treat (if necessary) water that is pumped from the NW <br />Panels Sealed sump. Mine water is pumped from the Lone Pine Gulch ventilation portal and <br />transported through a 12-inch HDPE pipeline. As the water has been of sufficient quality to <br />meet discharge limitations, it has been directly discharged to Lone Pine Gulch, and subsequently <br />2.05-~13 Revised Sep. /996 MR195 ,July 2001 TR-93 <br />21 <br />