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(3) Protection of Hydrologic Balance <br />(a)(i) The applicant has prepared a drainage and sediment control system which <br />will minimize changes to the surface water and to the prevailing hydrologic <br />balance in the facilities area by detaining run -off in sediment ponds or <br />treating runoff with alternative sedimentation control. The sediment ponds <br />are designed to contain the run -off from the 10 year precipitation event. The <br />sedimentation control plan is presented in Volume III, Exhibit 8, and on Maps <br />20, 21 -1, 21 -2, 21 -3, 21 -4, 22 -B, 22 -C, 22J, 22 -K, 35, 36, 36a and Volumes <br />IV, IX and XI. <br />There is very little if any beneficial use made of surface run -off from the <br />ephemeral drainages in the permit and adjacent areas. These ephemeral <br />drainages typically only flow during spring snowmelt and significant <br />precipitation events. Sediment ponds B & C should alleviate the problem of <br />the ditches (Deer Trail Ditch & Fire Mountain Canal) plugging with sediment <br />and /or completely washing out do to previously uncontrolled runoff events. <br />The construction of mine entries, ventilation shafts and the mining of the coal <br />could cause water to move from formations above the coal seam into the <br />mine. This potential water migration would be magnified by roof collapse and <br />fracturing caused by subsidence. Although the permeability of the coal seam <br />and surrounding strata is low and the quantity of water stored in the formation <br />is also low, some water will occasionally seep into the mine. <br />The Freeman Gulch vent shaft was raise bored to an 8 -foot diameter. The <br />shaft was lined with a 6 -foot diameter steel casing. The steel casing was <br />grouted through the water bearing zone which is approximately 0 to 140 feet <br />deep. The grout liner through this zone is approximately 1 -foot thick. To <br />prevent surface drainage from entering the shaft, the steel liner was <br />extended at least 3 -feet above the ground surface (see Map 35). A screen <br />was placed on the top of the steel liner. The Freeman Gulch shaft has been <br />backfilled a capped with concrete. This backfill will protect the integrity of the <br />grouted liner to contain the water bearing zone. The concrete cap will ensure <br />no surface run -off will enter the backfilled shaft. Thus, the shaft backfill and <br />concrete shaft will protect the hydrologic balance. <br />MR-168 2.05-106 12/14 <br />