2010-09-20_PERMIT FILE - C1996083A (7)

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0 2.05.6 (3) Protection of Hydrologic Balance (a)(I) The applicant has prepared a drainage and sediment control system which will minimize changes to the surface water and to the prevailing hydrologic balance in the facilities area by detaining run-off in sediment ponds or treating runoff with alternative sedimentation control. The sediment ponds are designed to contain the run-off from the 10 year precipitation event. The sedimentation control plan is presented in Volume III, Exhibit 8, and on Maps 20, 21 -1, 21 -2, 21 -3, 21-4, 22 -13, 22 -C, 22J, 35, 36, 36a and Volume IV. There is very little if any beneficial use made of surface run-off from the ephemeral drainages in the permit and adjacent areas. These ephemeral drainages typically only flow during spring snowmelt and significant precipitation events. Sediment ponds B & C should alleviate the problem of the ditches (Deer Trail Ditch & Fire Mountain Canal) plugging with sediment and /or completely washing out do to previously uncontrolled runoff events. The construction of mine entries, ventilation shafts and the mining of the coal could cause water to move from formations above the coal seam into the mine. This potential water migration would be magnified by roof collapse and fracturing caused by subsidence. Although the permeability of the coal seam and surrounding strata is low and the quantity of water stored in the formation is also low, some water will occasionally seep into the mine. The Freeman Gulch vent shaft will be raise bored to an 8 -foot diameter. The shaft will be • lined with a 6 -foot diameter steel casing. The steel casing will be grouted through the water bearing zone which is approximately 0 to 140 feet deep. The grout liner through this zone will we approximately 1 -foot thick. To prevent surface drainage from entering the shaft, the steel liner will be extended at least 3 -feet above the ground surface (see Map 35). A screen will be placed on the top of the steel liner. The Hubbard Creek vent shaft was blind drilled to a 14 -foot finished diameter. The shaft was steel lined to a finished diameter of 12 -feet. The 500 foot deep shaft was grouted through water bearing zones. To prevent surface drainage from entering the shaft, the concrete collar was extended above the ground surface. During idle periods, a screen is placed on the top of the concrete shaft. Because of the method of shaft construction, there was no measurable water, inflow during shaft construction. The pre - grouting and shaft liner were effective in stopping groundwater from entering the shaft. There is no flow at the bottom of the shaft. The quality of ground water that comes in contact with coal seams and surrounding strata is generally degraded. Bear Coal Company prepared a study of the potential effects of mining on the B -Seam aquifer (J. E. Stover & Associates letter to DMG dated October 23, 1995). A correlation was made between the geochemical characteristics of the roof, coal and interburden and the degradation of the quality of water in the coal seam. Soluble calcium, magnesium and sodium appears to degrade the quality of ground water that comes in contact with the disturbed coal seam and surrounding strata. This degradation of ground water quality is considered typical for water which seeps into the mines in the Paonia Somerset area. • MR -113 2.05-67 10/09 PPRaV6� II11Z1 a