Laserfiche WebLink
RULE 2 - PERMITS <br /> At YSG5, the proposed downstream compliance point under SMCRA, ambient iron concentrations <br /> were diluted by the mine effluent to 97% of the previously measured concentration. It should be <br /> noted that reported iron concentrations are affected by variable detection limits (0.02 to 0.1 mg/L), <br /> and the use of the detection limit in averaging where the laboratory reported "less than" values. At <br /> downstream compliance point YSG5, measured summer low flows were as low as 20 gpm, due to <br /> reinfiltration of surface water into valley alluvium. Mixing calculations at YSG5 are therefore of <br /> questionable precision. <br /> Discharge of mine-affected groundwater to alluvial aquifers will have negligible effects. As <br /> estimated in the discussion above, the inflow of poor-quality groundwater to the alluvial aquifer <br /> would only be 0.046 gpm, less than a tenth of a percent of the combined dry-season spoil spring <br /> discharge (66 gpm in September 2005) in the Little Grassy Creek basin, and less than two-tenths of <br /> a percent of the measured summer low flow in Little Grassy Creek (28 gpm at Pond 002). <br /> Exposure of materials by mining-related surface disturbance and contact of disturbed area runoff <br /> with these materials, infiltration and drainage from coal storage any potential surface discharge of <br /> excess mine drainage flows may result in changes in runoff or discharge water chemistry. Exposure <br /> of natural geologic materials (surficial rock, overburden, and soils) and both mine spoils and <br /> reclaimed mine areas from previous surface mining activities to surface runoff and infiltration are <br /> recognized sources of elevated iron, selenium, and TDS in the area. Surface water in the mine area <br /> is generally a calcium-sodium, mixed-anion type, although chemistry may vary to include calcium- <br /> magnesium mixed anion, sodium-potassium bicarbonate, and sodium-potassium mixed anion types. <br /> The most probable potential change in runoff water chemistry would be a shift from a mixed anion <br /> type toward a calcium-magnesium sulfate type due to the weathering and leaching of exposed <br /> surface materials. Additionally, as discussed above, mine inflow discharges may contribute <br /> additional iron to surface water under some circumstances, while not exceeding water quality <br /> standards. Mine inflows would actually dilute ambient TDS concentrations in surface waterways. <br /> PSCM's proposed surface drainage and sediment control measures, specifically limitations on total <br /> surface disturbance and collection of disturbed area runoff as close as reasonably feasible to the <br /> disturbance source area, will be effective in limiting runoff exposure to stockpiled materials and <br /> consequent leaching. The fact that the materials which will be exposed, including overburden, <br /> soils, coal, and mine development waste materials, have been determined as not potentially acid- or <br /> toxic-forming (Section 2.04.6) is an important factor which will also limit the potential for any <br /> significant changes in surface water chemistry. <br /> While minor changes in surface water chemistry may occur as a result of mining and related <br /> operations, limited surface disturbance areas, corresponding limited disturbed area runoff volumes, <br /> and consumptive use of mine water discharge will minimize any potential for significant changes in <br /> water chemistry for the receiving drainages. In addition, disturbed area runoff and any residual <br /> mine water discharge flows will be buffered by significantly greater volumes of normal runoff from <br /> undisturbed drainage basin areas during most times of the year. Potential increases in TSS levels <br /> will be effectively addressed on a short-term basis by establishment and operation of the drainage <br /> and sediment control system, consumptive use of mine water discharge, and compliance under the <br /> required CDPS permits with applicable monitoring requirements and discharge effluent limitations. <br /> Reclamation and restoration of effective surface drainage conditions will address all potential <br /> mining and related surface water impacts over the long-term. Culvert installation and diversion <br /> construction may temporarily affect surface drainage patterns, and construction activities may result <br /> in increases in sediment contributions both during construction and for a short period of time <br /> RN15-01 2.05-90 Revision 10/17 <br />