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2.04.7 Hydrology Description <br />• holes were drilled with mud, such that the static water level recorded should <br />be considered dubious at best. Any holes drilled with bentonite based mud <br />can greatly inhibit the hydrologic properties due to mud cake within the drill <br />hole. When air and foam are used as a drilling medium, the hydrologic <br />conditions of the in -situ rock are virtually unaffected, and observation of <br />subtle inflow or lost circulation zones are greatly enhanced. The progress of <br />these holes was monitored in the field and recorded by competent personnel. <br />West of Terror Creek the geohydrologic setting changes. The "D" coal seam <br />is not identifiable and faults are present that complicate groundwater level <br />projections west of Terror Creek. West of Terror Creek the water bearing <br />zones of concern are the zones in the B -Seam and above the B -Seam. Map <br />10A depicts the potentiometric surface above the B -Seam and Map 10B <br />depicts the potentiometric surface in the B -Seam. Map 10A, potentiometric <br />surface above the B -Seam is a more regional projection than Map 10. Map <br />10 uses specific wells in order to project groundwater contours above the D- <br />Seam. The potentiometric surface shown on Map 10A utilizes groundwater <br />elevations, regional dip and faults in order to project groundwater elevations <br />east and west of Terror Creek. <br />Although no data for permeability or transmissivity of the saturated portions <br />of the coal bearing member of the Mesaverde Formation are available within <br />• the permit area, the experience by others (Brooks, 1983) suggests that the <br />Mesaverde Formation transmits little water. Mountain Coal Company reports <br />a yield of 3 gpm from the 245 interval of the Rollins Sandstone from its <br />monitoring well R -1 (MCC permit section 2.04.7). The primary (granular) <br />permeability is low due to the lithologic composition of the sandstone and the <br />secondary (fracture) permeability is not well developed. Extensive core <br />drilling within this strata shows that fracture zones are not well developed. <br />Similar observations were made in the Orchard Valley underground mine by <br />CWI. Fracture zones or zones of lost circulation during drilling do not appear <br />to extend from hole to hole. Fracture and fault zones, although encountered, <br />are not well developed. <br />Potential recharge to the Mesaverde Formation occurs within the major <br />stream drainages, while flowing, (Brooks,1983). Recharge may also <br />originate in the colluvium or colluvial water recharges of the shallower <br />Mesaverde Formation lithologies. The alternating lenticular channel <br />sandstone and enclosing overbank claystone lithologies within the upper <br />Mesaverde Formation has the potential to create perched water table <br />conditions within the permit area. These conditions, which are a function of <br />the deltaic fluvial depositional environment, are characterized by confined, <br />saturated horizons of localized lateral and vertical extent within low porosity, <br />unsaturated intervals. These perched, confined horizons may exhibit artisan <br />• conditions; however, flowing conditions were not observed within the permit <br />area. Additional recharge of much smaller magnitude could occur at the <br />PR -12 2.04-35- 06/10 <br />A PPAowcD <br />II/f41to <br />