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<br />The Mahogany Zone is located between the upper and lower portions of the aquifer <br />• system. While it is not impermeable, the Mahogany Zone does serve as an aquatard <br />and provides additional protection from poor quality water in the Lower Aquifer <br />migrating upward into the Uinta Formation portion of the Upper Aquifer. <br />Furthermore, the integrity of the Upper Aquifer, including that of the potential <br />USDW, would be preserved throughout American Soda's proposed commercial <br />mine operations. As discussed in Section 3.1.3, American Soda's analysis of <br />subsidence indicates that subsidence will not adversely affect the USDW under even <br />a worst-case scenario (Agapito 1998). <br />As a result of these factors, the aquifer system should be adequately protected, and <br />no significant impacts to the potential USDW are anticipated. <br />Protection of the potential USDW will be further ensured by the establishment of a <br />series of monitoring wells in the well field to monitor potential environmental <br />impacts of the mining process on underground formations and groundwater <br />aquifers. American Soda currently monitors the water quality of the Uinta <br />Formation directly by monitoring water supply well 20-8 and the downgradient <br />Uinta Formation monitoring well 20-5. Water quality results from samples taken <br />from these wells have not indicated any appreciable changes in water quality since <br />startup of the experimental test mine phase. Existing monitoring well 20-1 also <br />monitors the water level and quality of the Lower Aquifer immediately above the <br />Dissolution Surface. Monitoring of the Lower Aquifer provides early detection of <br />potential movement of fluids out of the solution mining interval, thereby <br />providing protection for the overlying Upper Aquifer, including the potential <br />USDW. As discussed in Section 4.3, these and other existing monitoring wells will <br />be used to monitor the 0-5 year mining panel; their locations are indicated in Figure <br />4-1. Additional monitoring wells will be established at appropriate downgradient <br />locations in conjunction with development of each subsequent 5-year mining panel. <br />It is anticipated that each panel will have at least one upgradient and one <br />downgradient monitoring well. These monitoring wells will most likely monitor <br />the Dissolution Surface because of its close proximity to the solution mining <br />interval (approximately 150 feet). Specific well locations and target monitoring <br />horizons for each well will be determined in consultation with the BLM. <br />Monitoring wil[ include water Level as well as water quality measurements and <br />analyses for all monitoring wells. Water quality analyses will include pH, <br />conductivity, total dissolved solids, alkalinity, sodium, bicarbonate, and carbonate. <br />Groundwater monitoring will occur on a monthly basis. Initial samples will also be <br />analyzed for the minor constituents listed in Tables 7-2 through 7-4, and these <br />minor constituents will be analyzed for if the Lower Aquifer is subsequently <br />affected. <br />American Soda currently monitors the water quality of the Lower Aquifer <br />immediately above the Dissolution Surface at monitoring well 20-1. As indicated <br />• <br />above, monitoring of the Lower Aquifer will provide early detection of any <br />American Soda, L.L.P. 8_12 <br />Commercial Mine Plan <br />August 18, 1998 <br />