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• disturbed by the Rimrock Coal Strip Mine and the ground water depths and <br />occurrence in the units disturbed by mining have not been identified to the <br />degree neceeaary for quantitative prediction. Neverthaleee, it doea indicate <br />that pit inflow rates will be relatively low. The water quality of these <br />inflows should be comparable to the water quality of the present underground <br />mine discharge as characterized by sample EMD and by the sample from the USGS <br />well completed in the Vermejo Formations. Actual dry season discharge should <br />be much lower since evaporation rates of less than 0.01 ft/day within a pit <br />area of about one acre would be sufficient to consume the entire estimated pit <br />inflow. The discharge during storm events and snowmelt would be <br />quantitatively more significant as described in Section 2.05.6.3.2. <br />Once mining activity ceases, post mining reclamation of the site will probably <br />increase the hydraulic conductivities in the vertical direction and decrease <br />hydraulic conductivities in the horizontal direction due to the obliteration <br />of the stratigraphic layering properties of the geologic formations. Even <br />with cementation and consolidation of the mine spoils which will be used to <br />backfill the mine pits, it is expected that the hydraulic conductivity in the <br />vertical direction will increase allowing somewhat greater recharge of the <br />underlying units. On the other hand, if reclamation results in the <br />establishment of a soil cover and vegetative cover comparable to that which <br />presently exists, the net recharge rates may actually be the same as these <br />features are significant components of recharge. <br />The mining operation will have no effect on the water storing and transmitting <br />capabilities of the Trinidad Sandstone since this unit will not be penetrated <br />or disturbed. Recharge of this unit should not change significantly provided <br />• a soil and vegetation cover similar to pre-mining conditions is established. <br />2.05.6.3.1.2 Quality <br />It is anticipated that sulfate and total dissolved solids concentrations in <br />the mine spoils may increase in comparison with the premining aquifer <br />conditions. This may occur as a result of: <br />1) exposing sulfide minerals in the previously undisturbed geologic units <br />to the surface and thereby promoting oxidation due to the abundance of <br />oxygen at the surface. This would tend to decrease pH levels which <br />would be neutralized by dissolution of carbonate materials. The net <br />effect is a increase in the concentrations of sulfate and total <br />dissolved solids in the spoil water. <br />2) changing groundwater flow paths from the more permeable geologic strata <br />to bulk porous media flow through spoils. This may result in enhanced <br />leaching of minerals released as a result of weathering of the spoil <br />materials. <br />The possible increase in the concentration of sulfate and total dissolved <br />solids in spoil water will have little significance on the water resources in <br />the mine area and adjacent area. Groundwater in the Vermejo Formation in the <br />mine area is not in use or likely to be used because of the poor quality and <br />limited yield. Recharge of the Trinidad Sandstone from the Vermejo is limited <br />as described in the baseline section. Furthermore since the spoil area <br />• represents such a small fraction of the area of the Vermejo Formation which <br />-2- <br />