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~ i <br />designed, constructed, tested, and certified to assure containment of the solutions in accordance <br />with the terms of the reclamation permit and the Rules. The ground and surface water <br />monitoring plans and mining system monitoring plans are designed for early detection of leaks <br />from the mining cavities, the solution mining wells and the surface piping. DMG has required <br />submittal of analyses of process solution chemistry that will be used to assure adequate design of <br />Environmental Protection Facilities. The chemistry of the process solution is held as confidential <br />information under Rule 1.3. <br />Comment #15: American Soda should provide site-specific studies that support the subsidence <br />scenario contained in the reclamation permit application and the studies should be made <br />available for public comment before a reclamation permit is considered. <br />DMG Response: DMG employs a practical approach to regulating subsidence, which stresses <br />monitoring verification of predicted subsidence phenomena and requires mitigating measures to <br />be implemented if subsidence in excess of predicted levels occurs or if the potential for material <br />damage is indicated. The applicant has provided a thorough evaluation of the potential for <br />subsidence at the solution mining site and has committed to a surface and subsurface monitoring <br />plan and triggering criteria for specific corrective measures in [he event significant subsidence is <br />detected. Not all of the subsidence prediction work can be released to the public because it is <br />necessarily based on the thickness of the ore body and overburden, which is information that <br />may be held confidential under Rule 1.3. The applicant has taken a conservative approach to <br />initial solution mining that will provide a high degree of assurance that subsidence that may <br />result in material damage will not occur. The first pass of solution mining through the mine <br />panels will be on a 600 foot well spacing (with an exception as described in the permit <br />application to provide sufficient solution for plant start-up). The final spacing of wells on 300- <br />foot centers will occur in a second pass. This will allow for evaluation of subsidence predictions <br />while there are still very substantial pillars in place between solution mining cavities. <br />Comment #16: There are numerous rich oil shale horizons in the solution mining intervals, <br />directly above the proposed solution mining horizons, within the leached zone, and above the <br />Mahogany zone that have been overlooked and not considered for protection of future <br />mineability. <br />DIVIG Response: The most important stratum to be protected from material subsidence damage <br />is clearly the Mahogany zone. It contains the richest oil shale deposits and also serves as a leaky <br />aquitard between the upper and lower aquifers. The subsidence monitoring and corrective action <br />plan provides specific protections to the Mahogany zone. If the Mahogany zone is protected <br />from subsidence damage, then the strata vertically above it will also be protected. The leached <br />zone is already rubblized by natural leaching and removal of evaporites. The subsidence action <br />plan requires lowering the solution mining interval if significant subsidence is detected between <br />the mining interval and the dissolution surface. It is difficult to establish what effect solution <br />mining of nahcolite will have on the future mining of oil shale in the solution mining interval. <br />What is clear is that under any currently feasible scenarios, mining of oil shale in the saline zone <br />would post-date mining in the Mahogany zone, which is an enormous resource, and that any <br />consideration of oil shale mining in the saline zone is decades away. To preclude mining of <br />