2008-07-10_PERMIT FILE - M2008006 (5)

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6. In Exhibit S, the applicant notes a number of structures within 200 feet of the proposed mine. Please locate all of the structures on the maps and note the proposed off-set mining distance from the pit to each structure. 7. What protection measures will be used to ensure that spills of asphalt and/or concrete materials will not contaminate the surface or ground water? Will concrete trucks be washed-out on site? If so what measures will be taken to contain the wash water? In the event of a spill, what measures will be taken to capture the spilled fuels/lubricants. Any protective berms should be designed to contain 100% of the volume of stored material. The Division recommends that the storage area(s) be located outside the floodplain. If it is necessary to have storage areas within the floodplain, the applicant must also describe protection measures that will be employed to contain the materials in the event of a flood. Rule 6.4.5 Exhibit F- Reclamation Plan 8. The applicant proposes to replace 4" to 6" of topsoil on the reclaimed areas. The soils information in Exhibit I note that topsoil depth in that area ranges from 11" to 15". The applicant should replace topsoil to a depth that at least meets the existing topsoil depth. Please commit to replacing topsoil to a depth of 11" over the reclaimed areas of the site or further justify the replacement depth of 4" to 6". Rule 6.4.7 Exhibit G- Water Information 9. The applicant states that the entire mine site lies within the 100-year flood plain of the Cache la Poudre River. In the event of a significant flood event (10-year flood or greater) it is likely that the existing pit will be captured by the Cache La Poudre River. Wherever mining will occur within 400 feet of the river channel, a flood analysis and flood control plan must be evaluated and submitted. This would include pit side armoring, river site armoring, inflow and outflow channels, or other appropriate measures. Accordingly, the Division requests that the applicant provide the flood elevations(s) to be expected under a "worst case" flooding scenario and specific mitigation measures that will be implemented to minimize the potential for any offsite impacts. 10. Rule 6.4.7(1) requires the applicant to directly state if surface water or ground water will be affected by the mining operation. The applicant noted registered wells within 600 feet of the affected land based on information obtained by the OSE However, a ground water study may reveal wells outside the 600-foot- radius that may be impacted. If so, these will need to be addressed and exhibits amended. In accordance with Rule 6.4.7(2)(b), the Division requests that the applicant identify and characterize the aquifer to be mined in or through. The Division also requests that the applicant define or predict the cone of depression or shadow and mounding effect expected for any areas to be dewatered and dry mined or as a result of installation of the compacted clay liner. The cone of depression and assessment of other effects should define, at a minimum, the horizontal and vertical extent of expected impacts. If during the assessment, the applicant determines that a drawdown, shadow or mounding effect will occur offsite that may impact a current groundwater user, the applicant must explain any mitigation measures to be implemented and trigger points that would put mitigation measures into effect. Typically, a trigger point of a 2 feet change from historic ground water levels is acceptable. 11. The applicant needs to describe how the drawdown of the pits and any shadowing/mounding effects will impact the structural integrity of the surrounding wells, surface water drainages, activities which rely on ground water in the vicinity of the site, and vegetation on or near the site (including the cottonwood trees in the riparian area near the Cache La Poudre River and the wetlands adjacent to the pits). The applicant must also describe any mitigation measures to be implemented and trigger points that would put mitigation measures into effect. 2