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DOCUMENT TITLE: Evaluation Of Stability And Potential Environmental Impact Of The <br /> Commercial Solution Mine Plan. <br /> 1. Every page of this document is labeled confidential. The operator should address why this is <br /> the case, and consult the regulations to determine which sections can be held confidential and <br /> which cannot. <br /> 2. Page 2-1. Section 2.0, last sentence, and several other locations. Please see comment #8 in <br /> the review notes for the Permit Application. The notion that dissolved nahcolite may <br /> reprecipitate upon cooling persists throughout the document, though it seems never to occur <br /> in any critical context. It appears that this notion has not been explored. The operator should <br /> run enough tests to quantify the notion before planning on such a process for mine protection <br /> purposes. The operator might also explore whether dissolved nahcolite will reprecipitate due <br /> to a drop in pressure, such as may occur within the return flow tubing. <br /> 3. Page 3-1 and forward. The operator should provide some evidence that the casing cement <br /> will bind to all of the rock types between the surface and the saline zone. In particular, we <br /> are interested in knowing that the cement will bind against halite and the high kerogen oil <br /> shales that will be intercepted, but also to the more ordinary rocks in the high salinity <br /> aquifers. <br /> 4. Page 3-2,13. The text notes that systematic outcrop mapping has not been completed on the <br /> Yankee Gulch lease, though a surface lineament map has been compiled by the USGS. The <br /> subsidence analysis models do not include models for a solution well to be developed in a <br /> zone with faults, fractures, or other vertical to sub-vertical discontinuities. It seems, <br /> therefore, that solution wells should be sited only in areas that are geologically consistent <br /> with the subsidence modeling assumptions, which means areas of no faulting or significant <br /> fracturing. The text does not appear to indicate that faulted or fractured areas or areas <br /> transected by lineaments will be avoided for solution mining, even though it would appear <br /> prudent to avoid such structures. This seems particularly necessary for the Piceance Creek <br /> area because this is a groundwater discharge zone and such water must be moving upwards <br /> via faults and fractures. <br /> Please address whether a geologic map will be constructed prior to mining and used to site <br /> the production wells. State what other measures may be taken to avoid siting wells in <br /> geologically susceptible zones, or whether such measures need to be taken at all. <br /> 5. Page 5-1 and forward. The report states here and elsewhere that the oil shale reserve to be <br /> protected lies only that within the Mahogany Zone. This may be the case for BLM <br /> requirements, but the Colorado Mined Land Reclamation Act requires that all natural <br /> resources be protected. In that regard, oil shale reserves within the saline zone are <br /> considered protected reserves. <br /> The text indicates that solution mining using high temperature waters will not degrade the oil <br /> shale. However, this is not demonstrated in the text. The DMG should be provided with <br /> tests showing that this conclusion is indeed the case. <br /> 6 <br />