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• until the coal has been removed. Following the short-term water level decline on the groundwater system as a result of pumpage of groundwater inflow to the pit, a potential long-term impact to the local groundwater flow is the period of time necessary for resaturation of the spoil material and reestablishment of aflow gradient. Spoil material at the New Horizon 2 mine will be replaced using techniques which will restore permeabilities of the material. Thus, the mining operation will not diminish vertical or horizontal permeabilities but may increase these permeabilities. As a result, there should be no significant impacts from the mining operation on groundwater flow and recharge rates. The time period required for the spoil material to resaturate should be greatly reduced because of the irrigation recharge as the mined area will be revegetated for an irrigation type of post mining land use. Containment of pit inflow and impacts on water quality. All runoff and pit pumpage from disturbed areas will be routed through sedimentation pond 007. The pond is designed and constructed to impound runoff and pit pumpage from areas disturbed by mining and provide sufficient residence time to insure that the pond discharge water chemistry meets the effluent requirements specified in the NPDES Permit. A review of the chemical and flow data indicates that • the potential for any discharge from Pond 007 to exceed receiving stream or federal standards is minimal. Past history of mine operations at the Nucla Mine indicate very few exceedances of the standards over the years of operations. As previously discussed, highest pit inflow is predicted to occur in year 5 at approximately 5,600 cubic feet per day. To assess the impact of this inflow on Calamity Draw and the San Miguel waterquality, itwas assumed thatthe entire flowwas discharged and that the TDS level for the overburden aquifer was representative of the chemical load. The duration of the water quality impacts is relatively short term (5 years) and the significance of the impact is negligible as TDS increases in the range of 0.08 to 1.5 percent are projected on the San Miguel River and Calamity Draw, respectively. These increases in TDS will be additional magnesium/sodium-sulfate type water which may result in a slight increase in salinity. These projected changes in TDS levels will in noway affect the present and potential uses of the surface water and are so small that they may not be measurable. Impact of saoil water quality on the ground and surface water quality. The available data indicate that a small proportion of the overburden may produce acid through the oxidation of pyrite. Based on laboratory tests on overburden cores, calcite is almost ubiquitous. Calcite serves two • functions, First, it buffers the pH of the water, which overall tends to slow the oxidation of pyrite, REVISED JULY 2006 2.04.7-51