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Establishing a thicker Injection Zone with these monitoring and protective measures will continue to <br />ensure protection of USDWs and prevent American Soda from violating their permit due to geologic <br />conditions. <br />Proposed Modifications for Injection Interval: <br />• Part II C (3) is proposed to be changed as follows: <br />Current Lan~ua~e: <br />Injection Zone. The injection zone is required to be a minimum of 150 feet below the Dissolution <br />Surface. The bottom of the injection interval will be approximately 800 feet below the Dissolution <br />Surface. The proposed injection zone (approximately 1,550 feet to 2,200 feet in depth at a surface <br />elevation of about 6,230 feet M.S.L.) is outside of and isolated from the major aquifer systems. This <br />zone is within the Saline Zone, which is located in the lower portion of the Parachute Creek Member of <br />the Green River Formation. The Parachute Member is the uppermost member of the four members that <br />make up the Green River Formation. <br />Proposed Language: <br />Infection Zone and Infection Interval. The Injection Zone extends from the base of the (but not <br />including R 6 zone down to approximately 800 feet below the Dissolution Surface. The Injection <br />Zone will also comprise the Dissolution Aquifer which immediately underlies the R-6 zone. The <br />Aquifer immediately overlying the Dissolution Surface does not generally meet USDW standards <br />within the mining area. The Injection Zone is below and separated from USDWs by the R-6 zone. <br />The Injection Interval is a unit contained within the Injection Zone. The Injection Interval equates <br />to the mining zone and is required to be a minimum of 150 feet below the Dissolution Surface to <br />approximately 800 feet below the Dissolution Surface. The Injection Interval (approximately 1,550 <br />feet to 2,200 feet in depth at a surface elevation of about 6,230 feet M.S.L.) is outside, of and isolated <br />from the major aquifer systems. This lies within the Saline Zone, which is located in the lower <br />portion of the Parachute Creek Member of the Green River Formation. The Parachute Member is <br />the uppermost member of the four members that make up the Green River Formation. <br />All injection of fluids for the purpose of mining will occur within the Injection Interval, although <br />the influence of this injection fluid is allowed within the entire Injection Zone. The permittee is <br />required to monitor ground-water aquifer conditions in accordance with the Water Monitoring <br />Plan (Appendix I) to ensure that mining fluids do not migrate out of the Injection Zone. In <br />addition to the requirements of the Water Monitoring Plan, American Soda will convert up to six <br />(6) mining wells to dissolution surface pressure-monitoring wells to enhance monitoring within the <br />injection zone as mining progresses within a mining panel. Therefore, EPA is requiring the <br />following actions. <br />FINAL Addendum to SOB For Modification No. 9, UIC Area Permit No. C030858-00000 Page 8 of 29 <br />