Laserfiche WebLink
2.7.5.2d Ground Water Quality, I and J Pits <br /> The relevant geologic units for the I and J Pits area are the same as those present mine wide. Sections <br /> 2.7.5.2 and 2.7.5.2a both contain relevant information to the area, particularly Section 2.7.5.2a. <br /> Three new monitoring wells, (CY1, CY2 and CY3)will be completed in the First,Second and Third White <br /> Sandstones, respectively, near Coyote Dam to monitor these aquifers during future operations. <br /> The water quality in the First White Sandstone aquifer downgradient of the mining in the area of the I <br /> Pit will be monitored at well CY1 and was previously monitored in the GLUX-1 well. The water quality in <br /> the GLUX-1 well was steady for the period of monitoring from 1988 to 2006 with chloride <br /> concentrations varying only from 10 to 20 mg/I over this nearly twenty years of monitoring. The water <br /> quality in the First White Sandstone aquifer at well GLUX-1 had not been affected by the upgradient <br /> mining because its outcrop is roughly 2000 feet north of the northern limit of the previous mining in the <br /> A and B pits.The water quality data from well GLUX-1 is thought to be a good baseline for this portion of <br /> the Trapper mining area for the First White Sandstone aquifer. The previous mining in the A and B pits <br /> to the south of the I and J pits has not affected the First White Sandstone aquifer in this area. <br /> The TDS and sulfate concentrations in the ground water for the GLUX-1 well downgradient of the <br /> proposed I Pit are presented in time plots in the AHR. These plots show that the water quality in the <br /> First White Sandstone aquifer has not been affected farther downgradient of the previous mining in this <br /> area. <br /> Water quality in two additional wells in this area of the Trapper Mine has been used to define historical <br /> concentrations downgradient of the A and B pits in the Second and Third White Sandstones aquifers. <br /> Well GE3 was completed in the Second and Third White Sandstones while well 81-03A was completed in <br /> the Third White Sandstone aquifer. The TDS plot from well 81-03A shows a very slight increasing trend <br /> from 1988 through 2006 which could be a very small impact from the historical mining in the A and B <br /> Pits on the Third White Sandstone aquifer. The TDS plot shows variations with time from historical <br /> monitoring in well GE3 but all of these values are less than the pre-mine values defined in well GE3. The <br /> completion of well GE3 is in both the Second and Third White Sandstone aquifers could be the cause of <br /> varying TDS concentrations from this well. The very slow movement of the ground water in these two <br /> aquifers will greatly limit the distance to where water quality changes are observed. The voids where <br /> the F and G coal seams are highwall mined should initially be filled with ground water from the Second <br /> and Third White Sandstone aquifers instead of water from the boxcut backfill area due to the depression <br /> in the water-level elevation in these two aquifers from the HWM in the I and J Pits. The recovered water <br /> levels in these two aquifers are not expected to extend into the backfilled boxcut areas due to the <br /> increased transmissivities in these two aquifers in the HWM area. Increases in TDS in the highwall <br /> mined area are not expected to be much above the adjacent aquifer water quality. Only partially <br /> saturated water movement should occur in the backfill area of the boxcut which should not affect the <br /> water quality in the northern highwall mined zone. The movement of the ground water in this northern <br /> zone is expected to be controlled by the small permeability of the adjacent aquifers and therefore <br /> Revision., A`/0 <br /> 2-520yy <br /> Approve z <br />