1988-04-11_PERMIT FILE - C1981008A (17)

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Protection and Mitigation Plan Introduction. The Probable Hydrologic Consequences analysis (Tab 17) did not conclude that there will be any potentially adverse hydrologic consequences from the Nucla East mining. The only impact identified as having any significance was the potential impact (diminished surface water flows) to surface water rights within the influence of the pit inflow drawdowns. A detailed augmentation and water rights plan is presented in Attachment 16-1 of Tab 16 and any potential impacts will be fully mitigated. In addition to the mining practices designed to minimize disturbances to the hydrologic balance previously discussed, comprehensive ground and surface water monitoring plans have been developed to assess the possible impacts to the hydrologic system identified in Tab 17, Probable Hydrologic Consequences (PHC). The results of the monitoring programs have and will continue to be employed to support the PHC conclusions that disturbances to the hydrologic balance will be minimal and that the potential uses of the ground and surface water systems affected by mining will not be changed. Additional ground and surface water monitors are proposed specifically to help insure that water rights are protected. Pending landowner and permit approvals, these sites will be incorporated into the monitoring program. The parameters analyzed for at each monitoring site as well as sampling and monitoring frequencies are documented in Tab 15, Hydrologic Monitoring Program. Table 18-1 shows which monitoring sites are utilized to address each of the probable hydrologic consequences discussed in Tab 17. The location of each of the monitoring sites can be seen on Exhibit 7-1 (Tab 7, Hydrologic Description). The following monitoring plan discussion will address how the monitoring data or programs will be used to determine impacts to the hydrologic balance. Ground Water Monitoring Plan. Overburden, Dakota Coal and Alluvial Aquifer Quantity and Quality. Future drawdowns in the overburden, coal and alluvial aquifers will be compared against multiple year predisturbance (baseline) average water level fluctuations at the 4, 2, 19, 9 and 14 proposed and existing spoils, alluvial, overburden coal and underburden monitoring wells, respectively. Water level fluctuations as a result of irrigation, natural and water quality sampling stresses have been reasonably defined. Significant water level drops 18-5 Revised 04/11/88