2014-11-17_PERMIT FILE - C1982056A (2)

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Hydrologic conditions for the Wadge /Wolf Creek Interburden and Wolf Creek Seam in the portion of the WCR underlying the NMD are generally similar to those characterized through previous baseline work and actually encountered for the Wadge Coal Seam and Overburden. Two monitoring wells installed in 2014 showed potentiometric surface elevations different from elevations for nearby wells in the Wadge Overburden but comparable in terms of the hydrogeologic conditions indicated by the wells. However, permeabilities determined for the Wadge /Wolf Creek Interburden and Wolf Creek Seam in the WCR were about 25 times lower than those of the Wadge Overburden (0.0016 ft/day for the Wadge /Wolf Creek Interburden and Wolf Creek Seam versus 0.04 ft/day for the Wadge Overburden). Twentymile Sandstone Aquifer Aquifer characteristics of the Twentymile Sandstone have been measured within the permit area in six wells, and the results for transmissivity are reported in a range of 0.25 to 32 WIday (Applied Hydrology Associates, 1984). Water levels of the Twentymile Sandstone have been monitored in the mine plan area in Wells 006 - BRDH -7, 006- 82 -48A, FBR -11 -B, FBR -12 -A, FBR -9 & 10, and FBR -2. Recharge, discharge, ground water movement, and water quality in the Twentymile Sandstone are discussed later in this section. The potentiometric surface map for the Twentymile Sandstone is presented as Figure 6R. Alluvial Aquifers The locations of significant alluvial deposits in the Foidel Creek drainage in the vicinity of the permit area are shown on Map 15, Alluvial Valley Floors and Surface Water Rights. A cross - section through the alluvial sediments near the confluence of Foidel and Middle Creeks is presented as Figure 6T. Ground Water Ouali The discussion of ground water quality will be limited to the aquifer units, which influence, or may be potentially affected by, the proposed mining operations. As shown by Exhibit 14, Hydrologic Monitoring, a number of ground water monitoring wells are completed in the significant aquifers of the Twentymile Park Basin in the permit and adjacent areas. Ground water levels and quality in some of these wells have been monitored since 1979. Bedrock Aquifers Water quality data from Well 001 -83 -106 indicates that the Trout Creek Sandstone aquifer baseline water quality is of sodium - bicarbonate type, with moderate sulfate concentrations and very low concentrations of calcium and magnesium. Total dissolved solids concentrations are in the range of 822 to 876 mg /1 and pH ranges between 8.7 to 9.0 units. Water quality in Well 001 -83 -107 is similar to water quality in Well 001 -83 -106. Known Uses of Ground Water A review of the Colorado State Engineers' records indicates the existence of several adjudicated wells within the general vicinity of the Permit Area. The wells are located within approximately a 2 -mile radius of the permit area (Exhibit 6H, Summary of Ground Water Rights). The location and completion information for these wells was examined to ascertain whether there is any potential for adverse impacts as a result of the proposed mining operations. The quality data from the Wadge Overburden wells indicate that ground water in this aquifer is characteristically of a sodium - bicarbonate type, with relatively low concentrations of calcium, magnesium, and sulfate. Total dissolved solids concentrations are typically in the range of 400 to 2,042 mg/1 and pH concentrations are 8.3 units (Well FBR - 11A). The four wells presently monitored under this permit as Wadge Overburden Wells (009 -79 -4, 006- 82 -74C, 91M006, and FBR -11 -A) have an average total dissolved solids concentration of 1,952 mg/1 and an average pH of 8.02. The average changes to 1,588 mg /1 total dissolved solids and a pH of 8.18 units, if monitoring Well 006-82 - 74C (located near the portal area) is excluded from the group. For monitoring Well 026 -79 -4, which is farther upgradient and outside the Permit Area, total dissolved solids concentration ranges from 384 to 1,510 mg/l, TR13 -83 2.04 -42 11/03/14