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CHAPTER 3- <br />~- EP7VIP.015'E1JTA.L I"PACTS OF THE <br />PPOPO~ED A.CT10i;5 <br />SHORT-TER~,1 COAL LEASE APPLICATIO"~ C-27432 <br />Air Quality <br />Except during the construction phase, the proposed action would not <br />increase particulate emissions or other air quality para~~zters at the <br />Orchard Valley Mine, but ~•~ould extend the time period during ~.:hich the <br />mine is a pollutant source for 8 years. Construction of the vent shaft <br />and access road r~ould temporarily increase particulates by a small <br />amount in the area disturbed and at the refuse disposal area. <br />Geologic and Geographic Setting <br />Topography <br />Construction and maintenance of the intake ventilation shaft ~:~ould <br />dist;~rb a tctal cf 1.6 acres by 1906 for level areas and cut-and-fill <br />StrUCtUreS aSSO Gated 'r;ith the aCCe55 read and gravel pad (less than <br />1/10 of 1 percent of the 864-acre tract). <br />Sinking the shaft would oenerate approximately X6;000 cubic yards <br />• of sandstone and shale rubble ,rYrich must be disposed of in acccrdance <br />with 3U(CFR):. E?7.71. <br />Subsidence features could occur due to extraction of a 12-foot <br />thickness cf the coal seam on the retreat or' ±he A sub^~ain. A maximum <br />of 10 feet or' subsidence could occur. Areas near the outcreo ~:~here <br />overburden is thin ~.ould be most vulnerable, particularly ir. the S!C; cf <br />Section 18 and the .iSPaPl1:' •!'-; or' Section 19 (T. 135. , R. 91:J. , 6th P.i•.. ). <br />Evidence of subsidence t:ould probably not begin appearine in the area <br />until 1982 or 1983 and could continue-for several decadzs but would <br />probably never aff=_ct ...ore than 20C acres (23 percent) of the 254 acre <br />tract. Extension cracks, subsidence pits, and compression bulees vrould <br />be the most probable expressions of subsidence (Dunrud 1976). <br />The area affected by subsidence is used primarily for ~:~ildiife <br />habitat and livestock grazing. It is unlikely that either use of the <br />area ~:~ould be affected. However, the ~•re ter holdine caaacity of a stock <br />" watering reservoir located in S1J'; of Section 18 (owned by CWI) r}'~ay be <br />destroyed. ' <br />A.s noted by Dunrud and Osterwald (1978) subsidence may also increase <br />the hazard of underground and surface fire and allo~~ the escape of <br />r 1 <br />LJ <br />