2013-01-29_PERMIT FILE - C1981022A (3)

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Section - 2.05.6 Ground water has accumulated in some of the underground workings associated with past mining operations. Water stored in the old mine workings, direct inflows to mine workings from the water table aquifer ox perched aquifers associated with the coal seams, and indirect drainage from any perched aquifers intercepted by subsidence fractures may all serve as potential sources of ground water inflow to the mine workings. In order to facilitate ongoing mining operations and assure safe operating conditions; OMLLC normally collects any significant mine inflows and transfers the resulting mine drainage to temporary underground sumps. Plans for handling mine drainage are described in Section 2.05.3, Mine Facilities. The possibility exists however, that mine workings, natural fracture systems, or mining-related subsidence fractures could intercept and result in rapid drainage of flooded mine workings or perched ground water reservoirs. Under these circumstances and if inflow rates and/or volumes exceed the capacity of the operational mine water handling system and underground sumps (approximately 600 gpm), emergency dewatering and drect discharge to an approved CDPS discharge point(s) could be necessary. Although not likely, under these circumstances OMLLC would immediately contact and seek and obtain any necessary emergency approvals from both the CDPHE and DMG prior to actual discharge. In conjunction with mine development activities for the Elk Creek Mine in the D-Seam, OMLLC will dewater both the alluvium/colluvium and the D Coal Seam in the immediate vicinity of the proposed development entries. The planned mine dewatering will occur over a relatively short time period during initial development and construction of the Elk Creek Mine and will be limited to the immediate vicinity of the Elk Creek surface facilities. Preliminary water quality data indicate that mine dewatering discharge will meet applicable CDPS discharge effluent limitations. This will be verified during actual discharge by regular sampling and analysis. Based on historic data and preliminary estimates of mine inflow volumes and mine water use requirements, it is anticipated that most if not all mine inflows can be either recycled through the operational mine water system or stored underground. Based on available sampling data for mine water inflows, stored mine water, and discharges from old mine workings, any potential mine water discharge is not expected to represent a significant water quality concern. If it becomes necessary to discharge any excess mine drainage or water from flooded mine workings to the surface, discharge .. will be normally limited to 600 gpm and would be routed through underground sumps to an existing CDPS discharge point(s). Mining and related support activities will require a consistent water supply with adequate capacity to meet all operational mine water supply requirements. Potable and sanitary water requirements for both the mine and the Town of Somerset, as well as mine use requirements, axe addressed through a water supply intake and treatment facility which draws water from an infiltration gallery on the bank of the North Fotk of the Gunnison River. Use of the North Fork as a water supply source has the potential of reducing stream flow downstream of the water supply intake. Potential mining-related impacts on stxeamflows in the North Fork will be mitigated by recycling mine drainage, effective utilization of water storage facilities to buffer water withdrawals during low flow periods, through the use of existing active water rights, and by the fact that the anticipated withdrawals represent a relatively small percentage of total stream flow. Rerycling of mine drainage to meet most operational rrtine water requirements significantly limits water supply withdrawal requirements. OMLLC currently has an underground sump in the Sanborn Creek Mine with a capacity of approximately 7.0 to ]0.0 million gallons and plans to construct an additional 3.0 to 5.0 million gallon underground sump in the Elk Creek Mine in conjunction with mine development activities. OMLLC's existing active water rights (two water rights of 0.9 cfs for a total of 1.8 cfs) provide significant excess water supply capacity beyond the projected maximum mine water supply requirements. Given that OMLLC does not anticipate that the full amount allowed under the existine water rights will actually be withdrawn, the available excess will serve as an effective buffer to limit potential impacts on downstream flows. Anticipated mine water supply uses are projected at less than 136.4-acre feet per year (0.188 cfs) as summarized by Table 2.05.6-T1, Projected Consumptive TR42 2.05-82 Revised January 2003