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2.7.5.1b Aquifer Characteristics, Eastern Expansion Area <br /> Trapper submitted PR-07 in May of 2013 with the intent to extend the perimeter boundary of the mine <br /> to the Knez Divide road, otherwise known as Moffat County Road 33. This small permit extension <br /> adjoins the active mine area and permit boundary as of 2013. The relevant geologic units in this <br /> expansion are present minewide. Sections 2.7.5.1 and 2.7.5.1a both contain relevant information to the <br /> area, particularly section 2.7.5.1a. <br /> Known geologic units within the eastern portion of the mine appear to continue to extend easterly in <br /> the Upper Unit of the Williams Fork Formation. Trapper has conducted extensive core drilling in the <br /> expansion area. The geologic setting is the same for the permit extension area as that presented in the <br /> Trapper Permit. Figure 2.7-4 in the Trapper Permit presents the structure of the basin in the area of the <br /> mine. Structure of the coal seams has been extended to cover the permit extension area. These <br /> structure maps show that the typical dip to the north in the northeastern portion of the Trapper permit <br /> area is changing to the northwest in Section 28 T6N R90W. This change fits the regional structure <br /> change that is shown in Figure 2.7-4. <br /> Using the projected structure maps of coal seam thicknesses, roof and floor locations the potentiometric <br /> water levels were extended to the east of the active mine area. Current levels are shown on Map M54 <br /> and the 2013 Annual Hydrology Report, (TR-113.) The structure maps for I and R coal seams were used <br /> to aid in the extrapolation of the water-level elevations for the HI and QR aquifers in the permit <br /> extension area. The structure map for the H seam was used in the extension of the water-level <br /> elevations for the Third White Sandstone because the base of this sandstone is near the top of the H <br /> coal. <br /> The water-level elevations in the QR aquifer were extended in the permit extension area accounting for <br /> the change in the dip of these beds from the north to the northwest. This structure change causes the <br /> water level contours to curve to the northeast in the permit extension area resulting in ground-water <br /> flow to the northwest instead of the northerly flow that occurs to the west of this area. Similar changes <br /> in the flow directions in both the HI and Third White Sandstone aquifers also occur in the permit <br /> extension area and to the north of the extension area. <br /> The anticipated water yield of the aquifers in the extension area should correspond with the <br /> determinations made in section 2.7.5.1a,Table 2.7-21b. Current monitoring wells completion <br /> information is contained in Table 2.7-20. The wells utilized in section 2.7.5.1a to determine aquifer <br /> characteristics are applicable to this area. A new series of monitoring wells will be completed in the <br /> expansion area to obtain better water level elevations and water quality data on the eastern edge of the <br /> mining area. However, present data suggest the water quantity will not be vastly different in the area <br /> when compared to data gathered in nearby existing wells. <br /> Wells such as GP-7 and GP-8 are located adjacent to the PR-07 expansion area. These two wells are now <br /> only beginning to experience impacts from mining to their west in L and K pits. The water quality data <br /> from these wells is a good baseline for the eastern edge of the mining area. Water quality in this area <br /> has not differed significantly from previous studies of the mining area. <br /> Revision: O7 <br /> JUI Q 8 2014 2-462m <br /> Approved: <br />