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contain? Is it a high temperature pond, and in that regard what protections may be needed to <br /> prevent access to humans or wildlife? What will be the composition of the pond residues <br /> and how will those residues be managed? A more detailed explanation of the processing <br /> might answer these questions. <br /> 4. Page G-8; top. The Operator concludes that "the only aquifer at the Piceance site that meets <br /> the definition of a USDW is the Uinta Formation (upper)portion of the Upper Aquifer. This <br /> conclusion is apparently based on TDS measurements in a single well, number 20-3. The <br /> conclusion implies, though it does not state explicitly, that the upper part of the Uinta is the <br /> only aquifer that needs USDW protection. <br /> There are other actual TDS measurements from this and other wells. Moreover, conductivity <br /> data were collected at a somewhat high frequency. Given the controversy over water quality <br /> in the upper and the lower aquifers in the region, the Operator should make a more detailed <br /> attempt to quantify conclusions about aquifer quality for the lower part of the upper aquifer <br /> and the lower aquifer. Provided the relationship between TDS and conductivity can be <br /> substantiated, then all conductivity values from all the local wells should be used to construct <br /> a conductivity-based TDS facies map, or other such construction, to identify the boundaries <br /> of waters with greater than 10,000 mg/L TDS. <br /> 6. Page G-10,13. The DMG agrees that there is a tendency toward supersaturation and mineral <br /> precipitation when solute-laden fluids cool. We question whether cooling alone will promote <br /> precipitation of the solids that will be dissolved by hot water that will be injected into the <br /> saline zone. Depending on the amount of water added, the saturation index might not be <br /> reached, even at surface temperatures, unless part of the water evaporates from the solute. <br /> Kinetics of precipitation also may play a role. <br /> In the present case, the potential adverse effects of fluid escape are considered to be minimal <br /> on the assumption that the dissolved nahcolite will reprecipitate upon cooling and heal <br /> fractures in the Uinta formation aquifer, thereby preventing injections of saline fluids into the <br /> upper aquifer. Given the low TDS in the upper aquifer, we consider this doubtful, but do not <br /> have enough information to evaluate the conclusion. <br /> If temperature-controlled reprecipitation of dissolved solids is to be considered a means to <br /> control leaks of process water into the upper aquifer, or other USDWs, the DMG would need <br /> to see evidence that such solids will form. We would anticipate that American Soda has <br /> conducted enough experiments to know with some degree of accuracy the temperature and <br /> solute concentrations that control nahcolite precipitation, and would be able to provide that <br /> information to support their conclusions. In any case, the DMG needs to know whether such <br /> a process is deemed to be a necessary means to control contamination of the USDWs. <br /> 4 <br />