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could be established such that the minimum intact pillaz width could be maintained while <br />maximizing resource recovery. Since no cavity shapes have been chazacterized to date, it could <br />be azgued that characterization should precede an approval to expand the maximum mining <br />diameters beyond 200 feet. <br />However, 29-24 is isolated from other solution-mined wells with no other completed wells <br />closer than 600 feet (measured from the center point of the well). According to the 2003 <br />Annual Report Map, the well pad for 29-50 has been constructed, but the solution mining well <br />has not been installed. The well pad of 29-50 is located 300 feet east of we1129-24. Other <br />proposed wells within 300 feet of 29-24 include wells 49, 57, 60 and 59. None of these well <br />pads or solution mining wells have been constructed to date. <br />Based on the rock mechanics information provided by American Soda and the fact that there are <br />no other mining and producing wells closer than 600 feet, DMG can approve mining of the well <br />29-24 cavity to a diameter of 225 feet based on volumetrics. However, no solution mining of <br />wells closer than 600 feet to we1129-24 can occur until after the 29-24 cavity has been <br />characterized. Since there is no restriction currently contained in the reclamation permit for <br />maximum cavity diameter, a technical revision does not appear to be necessary to make this <br />approval. <br />Once the we1128-21 cavity has been chazacterized, the thermal mechanical models from the <br />Agapito rock mechanics reports can be calibrated and any variations on cavity width over the <br />vertical profile can be evaluated. This information, and information from chazacterization of <br />other wells to occur in the future, can be used to establish, ultimately, the spacing for mining <br />wells and maximum cavity diameters that can be developed. <br />If you have any questions, please do not hesitate to contact me at 303-866-4943. <br />Si erelY, <br />.~ <br />Enca S. Crosby <br />Environmental Protection Sp ralist <br />cc: Cazl Mount; DMG (via e-mail) <br />Kent Walter; BLM <br />Paul Daggett; BLM <br />Dan Jackson; EPA <br />Elisabeth Evans; EPA <br />Sandy Stavnes; EPA <br />