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flow when sampled in July and September in 1986. The Wadge coal seam <br /> comprises roughly 5% of the aggregate thickness of likely permeable units in <br /> the outcrop belt, assuming the seam is 10 feet thick and the Trout Creek and <br /> Twentymile Sandstones are in aggregate 200 feet thick. If the coal seam's <br /> contributions to Grassy Creek flows are eliminated by PSCM's drawdown <br /> (which PSCM's analysis indicates is possible), and assuming the Wadge coal <br /> seam contributes 5% of the outcrop belt's total contribution to Grassy Creek <br /> flows, then PSCM's drawdown could reduce Grassy Creeks' flows by 1% (a <br /> 5%reduction of 20% of Grassy Creek's flow). A 1%reduction in flow in <br /> Grassy Creek will not be enough to impair the use of Grassy Creek water. <br /> There currently are no users of surface water on Grassy Creek. <br /> Underground mine water that accumulates in the down dip end of <br /> underground mine workings will seep into the unmined rock in the walls, roof, <br /> and floor of the workings. The quality of this leachate is expected to be <br /> similar to native ground water in the Wadge coal seam and the roof and floor <br /> rock because large amounts of gob (waste rock) are not expected to be <br /> produced during non-retreat room and pillar mining. PSC predicts that a <br /> plume of the mine water will advance outward from the workings at a <br /> maximum velocity of 11 feet per year, a slower velocity than predicted for the <br /> nearby Foidel Creek Mine in the previously mentioned U.S. Geological <br /> Survey report of Robson and Stewart. PSC predicts that seepage of <br /> underground mine water from the workings up dip into Grassy Creek <br /> alluvium after postmining recovery of the Wadge seam potentiometric surface <br /> will be less than 1 gallon per minute and will be too small to have a significant <br /> effect on alluvial ground water quality. <br /> Section 2.03.5 of the PSCM permit provides updated information in relation <br /> to selenium both naturally occurring and in the reclaimed mine spoils from the <br /> previous Seneca 11 mining operations. Additional factors relative to the PHC <br /> include current effluent limitations and existing wetland passive treatment <br /> systems which are effective in reducing selenium. The PHC has been updated <br /> to reflect current information. <br /> IV. Topsoil <br /> Baseline soils information is provided in Exhibit 2.04.9E-1 and on Map 2.04.9-M1 in <br /> the permit application. Exhibit 2.04.13-E2 shows the thicknesses of topsoil replaced on <br /> the lands that have been transferred from the Seneca 11 Mine permit area to the PSCM <br /> permit area. The average depth was 15.6 inches as indicated by 933 samples taken over <br /> 1,793.acres (one sample per 1.9 acres). <br /> During mining operations at the PSCM, available soil or suitable growth materials will <br /> be salvaged prior to disturbing lands. Section 2.04.9 and Exhibit 2.04.9-E1 identify <br /> target topsoil salvage depths. Large shrubs will be removed prior to soil removal. <br /> Smaller vegetation will be removed during soil salvage and will be incorporated into <br /> 17 <br />