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<br />~dSt ~id5 ti ng 15 utilized 'nh?n?var ~U »ibl? t0 dC C~?l erdt2 the bac!cfi'.ling <br />process and minimize handling of overburden. Spoil material grading is <br />performed within 180 days of coal removal to limit the extent and duration of <br />weathering. Dust suppression activities take place when climatic conditions <br />warrant to deter nun-point source siltation. Final smoothing of the fill is <br />followed by surface roughening to maximize avatar retention and provide a goad <br />bonding surface for topsoil. The applicant practices live topsoil placement <br />to minimize handling, further reducing soil loss. Topsoil placement is <br />followed by mulching with wood chips, chisel plowing and the construction of <br />contour furrows. These practices maximize water retention and minimize soil <br />loss. The applicant employs additional run-off erosional control measures in <br />problem areas. These include the utilization of straw bale barriers, check <br />dams and matting. <br />The sediment ponds which are used to prevent siltation outside the pernit area <br />do change the hydrologic regime of the drainage. The ponds slow the migration <br />of flow downstream and minimize the peak flows seen along the drainage. A11 <br />ponds are designed to provide a 24-hour settling period to enable discharging <br />waters to meet an effluent standard for suspended solids of 35 mg/1 average <br />and 70 mg/1 maximum during a 30-day period. The mine must also meet the <br />settleable solids standard of 0.5 ml/1 during a 24-hour period. These <br />S standards are far more stringent than the levels of suspended and settleable <br />[~r~~l solids in undisturbed drainages. <br />'va ~ <br />U' Total dissolved solids (TDS) levels will increase as a result of mining. The <br />applicant indicated that this is a consequence of two different, but related <br />phenomena. During active mining operations the increased runoff volumes <br />provide more solvent to leach the newly exposed, unweathered overburden. <br />Following regrading, the backfilled overburden is exposed to more water due to <br />ground water ponding in the rubble. This increases the weathering intensity. <br />Additionally, the number of sites (surface area) available for weathering in <br />the rubble has increased over sites available in lithified material. This <br />results in an increase in salts in ground and surface waters near the mine. <br />TDS levels of spoils aquifers vary as a function of several factors, none of <br />which are completely understood. TDS levels do depend on overburden <br />lithology. Chemical weathering of the Lewis Shale overburden overlying the <br />Fish Creek seam at Mine 2 has resulted in spoils aquifer water with TDS levels <br />ranging from 324 - 1,042 mg/1, TDS levels may also be influenced by <br />operational procedures. Mine 2, Hayden Gulch and Grassy Gap were all truck <br />and shovel operations and have lower TDS levels than many area mines. Each <br />mine recovered a different coal seam and disturbed different overburdens. <br />Residence time may also affect salt concentration, although there have been no <br />studies of this to date. <br />The water quality of surface mine runoff and spoils spring water is tabulated <br />in Table 9 and compared with existing receiving stream standards. The Area 2 <br />Pit water quality represents both a spoils spring contribution and surface <br />water runoff contribution across disturbed lands. Pond F reflects spoils <br />spring water quality. The Area 2 Pit water is less saline than Pond F, as a <br />consequence of dilution from surface water runoff. <br />d0 <br />