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• 5. Protection and Mitigation Plan <br />Introduction <br />The only impact identified as having any significance at the New Horizon 2 mining area was the <br />potential impact (diminished surface water flows) to surface water rights within the influence of the <br />pit inflow drawdowns. A detailed augmentation and water rights plan is presented in Peabody <br />Attachment 16-1 and any potential impacts will be fully mitigated. <br />In addition to the mining practices designed to minimize disturbances to the hydrologic balance <br />previously discussed, comprehensive ground and surface water monitoring plans have been <br />developed to assess the possible impacts to the hydrologic system. The results of the monitoring <br />programs have and will continue to be employed to support the conclusions that disturbances to <br />the hydrologic balance will be minimal and that the potential uses of the ground and surface water <br />systems affected by mining will not be changed. Additional ground and surface water monitors are <br />proposed specifically to help insure that water rights are protected. Pending landowner and permit <br />approvals, these sites will be incorporated into the monitoring program. <br />• The following monitoring plan discusses how the monitoring data or programs will be used to <br />determine impacts to the hydrologic balance. <br />6. Ground Water Monitoring Plan <br />Overburden, Dakota Coal and Alluvial Aquifer Quantity and Quality. Future drawdowns in the <br />overburden, coal and alluvial aquifers will be compared against multiple year predisturbance <br />(baseline) average water level fluctuations. Water level fluctuations as a result of irrigation, natural <br />and water quality sampling stresses have been reasonably defined. Significant water level drops <br />outside these multiple year ranges will be considered to be possible effects from pit pumpage. <br />Water level drops in monitoring wells outside the projected zones of pit pumpage drawdown will. <br />be considered suspect unless a consistent deepening trend develops. <br />Mining impacts on ground water quality will be compared against the multiple year baseline <br />monitoring ranges established for each chemical parameter monitored at each site, Because a <br />number of variables can affect water chemistry, only significant increases or consistent trends will <br />be considered as possible impacts from mining. <br />Spring Flows and Quality. Spring flows and quality changes at spring monitoring sites will be <br />• compared to ranges developed from multiple-year baseline monitoring data. Significant flow or <br />(Revised July 2006) 2.05.6(3)(b)(v)-7 <br />