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<br />During commercial mining operations at the Piceance Site, mining solutions will be <br />• pumped into and out of solution mining cavities in the Saline Zone. <br />Communication of these nahcolite-bearing mining solutions with overlying strata <br />could result in potential water quality impacts to the Uinta Formation portion of the <br />Upper Aquifer, which is considered to be a potential Underground Source of <br />Drinking Water (USDW). However, there are a number of specific measures <br />proposed by American Soda, as well as site conditions, that will minimize the <br />potential for impacts to the Uinta Formation portion of the Upper Aquifer. <br />First and foremost, it is imperative to recognize that maintaining a pressurized, <br />confined system is essential to American Soda's mining process. If leakage from the <br />cavities were to occur, there would be a corresponding loss of pressure, and the well <br />would have to be shut in and corrective action taken. Pressure at each well will be <br />continually monitored so that, if a leak were to occur, it would be detectable almost <br />immediately, and corrective action would be taken. <br />Secondly, the wellbore (intermediate) casing will be set to about 150 feet below the <br />lowermost extent of the aquifer layers (Dissolution Surface). The casing will be <br />cemented to surface with aheat-resistant cement to isolate the aquifers. Mining <br />fluids will be further contained within a tubing system inside the casing. American <br />Soda has provided a buffer zone of about 150 feet of rock between the top of the <br />mining zone and the lowermost extent of the aquifer layers specifically to protect the <br />• aquifers from potential communication with the solution mining wells. <br />Thirdly, site conditions are conducive to protecting the Uinta Formation portion of <br />the Upper Aquifer. The mining interval is a confined zone with generally <br />competent, high-quality rock that is not easily fractured. The Lower Aquifer does <br />not meet the proposed Colorado standard for drinking water because of high <br />concentrations of fluoride, arsenic, cadmium, chloride, iron, mercury, manganese, <br />lead, and selenium and marginal pH. Elevated levels of barium, boron, lithium, <br />copper, chromium, and strontium are also common. The Lower Aquifer does not <br />meet the standards for irrigation water because of excessive molybdenum and <br />fluoride and marginal pH. Therefore, this water is considered unusable, and any <br />impacts to the Lower Aquifer from solution mining activities would be negligible. <br />The existing water quality in the Lower Aquifer is largely the result of natural <br />dissolution of the minerals in the Saline Zone. Total dissolved solids (TDS) levels <br />are extremely high, and, near the Dissolution Surface, the water is highly <br />concentrated with sodium bicarbonate/sodium carbonate. If mining fluid were to <br />escape the well, it would rapidly cool, become supersaturated, and precipitate the <br />sodium minerals. In the case of a fracture, this precipitation of minerals would be <br />likely to effectively plug and seal the leak. Even if fluid were to enter the Lower <br />Aquifer, mixing with ambient water would speed cooling and precipitation. The <br />primary effect would be deposition of sodium minerals along the Dissolution <br />• Surface, the very location from which they are being naturally dissolved. <br />Amencan Soda, L.L.P. 8_11 <br />Commercial Mme Plan <br />August 1R. 19913 <br />