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4.0 Environmental Background <br />4.1 Geolo ig cal S,~ttin~ <br />Coal is mined from the Mesa Verde Formation geologic offset, where the cover over the coal can <br />range from zero at the outcrop to over 2,000 feet deep. The strike of the coal beds is north 70 <br />degrees west (290 degrees) with a dip of 3 degrees to the northeast. Coal units within this <br />formation are highly faulted as mining depth increases. The geology (Figure 1), geologic <br />structure, and stratigraphic sections (Figures 2 and 3) suggest the amount of transverse faulting <br />appears to be increasing in numbers with depth. Figure 4 shows coal bed and lithologic <br />nomenclature. Figure 5 is an illustration of geologic cross section of the mine site. Access to the <br />coal from the outcrop is difficult due the extensive burn zone. <br />4.2 Hydrolo ig c Setting <br />Hydrologic studies conducted by Westmoreland Resources and more recently by Bowie indicate <br />that there is no bedrock ground water domestic or agricultural supply wells within the permit <br />area. This is attributed to the low permeability of the water bearing strata, the lenticular nature <br />of the sandstone strata, the excessive depth (greater than 300 feet), and the generally poor quality <br />of water. Ground water is recharged by direct infiltration and runoff at outcrops and subcrops <br />underneath the colluvial sediments, where saturated. Ground water flow follows the dip of the <br />bedrock strata; however, the flow amount and rate is very slow due to the low transmissivity/ <br />permeability and the limited amount of water infiltrating the ground water aquifer system. <br />Ground water is unconfined near the outcrop and becomes confined down dip. Ground water in <br />the bedrock aquifer contains bicarbonate, sodium, and sulfate with total dissolved solids (TDS) <br />ranging from 400 to over 10,000 mg/1. TDS concentration increases with depth. <br />As DRMS notes iin "Proposed Decision and Findings for Compliance for a Mining and <br />• Reclamation Permit -Permit Revision No. 9 -October 11, 2005," the impacts to ground water <br />"within the permit area should be minimal, due to the relative lack of useable ground water and <br />due to the vertical separation which exists" between coal seams and the "Rollins sandstone. The <br />Rollins sandstone-, the major aquifer within the study area, [is) located considerably below the <br />~ mining elevation (Figure 1). Local alluvial systems down gradient from the mine should not <br />• receive sufficient mine water drainage to create any impacts." Water produced from the mining <br />areas, both historiically and currently, is generally less than 70 gallons per minute (gpm). Most <br />of the water appears to be entering the mine workings from low permeable joints or fractures in <br />the underground mine roof rock. The quantity of water entering the mine workings decreases <br />• over time. Data suggests ground water infiltrates the mine area at a rate of less than 0.02 gpm <br />per acre. Table 1 summarizes ground water mine production, where the total water yield from the <br />underground operation with a footprint in excess of 3,300 acres ranges from 7 to 70 gpm and <br />annually averaging less than 30 gpm. Most of the water generated underground is used to control <br />• dust. Because recharge from the aquifer sandstone outcrop and shallow alluvial aquifer system <br />. is negligible, watf;r appears to be entering the mine area from isolated perched water producing <br />zones above the mine workings. <br />.~ <br />3 <br />