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2.7.5.1d Aquifer Characteristics, I and J Pits <br /> Mining of the F and G coal seams in the I and J Pits, respectively, will be located in the West Panel of the <br /> mine in the No-Name, Coyote and Buzzard Gulch drainages. The primary means of coal removal will be <br /> highwall mining from the initial boxcut to the north of the I and J Pits. The relevant geologic units in the <br /> I and 1 Pit area are the same as the remainder of the Trapper mine with the First,Second and Third <br /> White Sandstones being the most important geologic units. Sections 2.7.5.1 and 2.7.5.1a both contain <br /> relevant information to the area, particularly Section 2.7.5.1a. <br /> Known geologic units within the I and J Pits will be the F and G coal seams in the Upper Unit of the <br /> Williams Fork Formation. The F seam lies on top of the Second White Sandstone and below a shale layer <br /> located at the bottom of the First White Sandstone.The G seam lies at or near the top of the Third <br /> White Sandstone and below the shale between the Second and Third White Sandstones. Each of these <br /> sandstone layers produce aquifers to the north of the pit area. Trapper previously had monitoring wells <br /> to the north of the I and J Pits in the First White Sandstone (GLUX), and the Second and Third White <br /> Sandstones(GE3),that define the water levels and water quality for these ground-water systems. An <br /> existing Third White Sandstone well, 81-03A,was also monitored from 1987 to 2006. The geologic <br /> setting is the same for the I and J Pits area as that presented in the Trapper Permit. Figure 2.7-4 in the <br /> Trapper Permit presents the structure of the basin in the area of the mine. The dip of the coal seams is <br /> to the north in this area of the Trapper permit and controls the flow of the ground water to the north. <br /> The transmitting aquifer properties(permeability and transmissivity)for the Trapper Mine are <br /> presented in Table 2-1 in the 2006 Trapper annual report. The transmissivity for the First White <br /> Sandstone from the GLUX-1 well was measured at 25 gal/day/ft which is similar to other values from the <br /> White Sandstone aquifer from the Trapper Mine. Some areas in the White Sandstone aquifers contain <br /> larger transmissivities. <br /> The water-level elevations in the First,Second and Third White Sandstone aquifers are updated in the <br /> Trapper Annual Reports. The historical water-level elevations in the White Sandstone aquifers in the <br /> western portion of the Trapper mine indicate the head in the Third White Sandstone is likely the highest <br /> in this area with heads near 6400 ft-msl in the outcrop area to the south and an elevation of 6322 ft-msl <br /> at well 81-03A. Water-level elevations in the First White Sandstone are likely the lowest of the three <br /> aquifers due to the outcrop areas existing at a lower land surface elevation. The 2006 water-level <br /> elevation in First White Sandstone well GLUX-1 was 6253 ft-msl. Water-level elevation in the First White <br /> Sandstone aquifer near the I Pit boxcut is likely near 6300 ft-msl. The anticipated water yield of these <br /> aquifers in the I and J Pit area should correspond with the determinations made in Section 2.7.5.1a, <br /> Table 2.7-21b. Current monitoring wells completion information is contained in Table 2.7-20. The wells <br /> utilized in Section 2.7.5.1a to determine aquifer characteristics are applicable to this area. <br /> Revision _P/� -�o <br /> 2-462o Approveo. :,._ <br />