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J~~tED Siq~ <br />~m ~ ~ <br />o <br />W <br />sign, n~ <br />~ O~. i>rn~ <br />UNITED ST <br /> <br />MENTAL <br />999 18i" STREET -SUITE 300 <br />DENVER, CO 80202-2486 <br />Phone 800.227-8917 <br />h ttp://www.epa. g ovlreg i o n08 <br /> <br />MAR 62003 <br />Ref: 8P-W-GW <br />CERTIFIED MAIL <br />RETURN REQUESTED <br />RECEIVED <br />MAR 01 2003 <br />Division of Minerals and Geology <br />Mr. Ed Cooley <br />Environmental Health and Safety Manager <br />American Soda, L.L.P. <br />2717 County Road 215 <br />Parachute, Colorado 81635 <br />Inc. Na~~-~ ~n~ 2c~~~~on y~/L'~~ AtO.~~~Ol,r~S <br />eq ~ ,'~ e ..-, U,~ts <br />a~-f ,'o .-, -tr ~'S< <br />a,~ 0~ ~-o r.1 ct ~' ~ .~C <br />~ JS <br />RE: LINDERGROUND INJECTION CONTROL (UIC) Program: <br />Approval of Minor Modification No. 6 to Class III Solution <br />Mining Wells, Adding Requirements for Analysis of Monitoring <br />Data and Criteria for Possible Corrective Action, Yankee Gulch <br />Site, EPA Area Permit C030858-00000 Rio Blanco County, <br />Colorado. <br />Dear Mr. Cooley: <br />The Environmental Protection Agency (EPA) has received your February 7, 2003, letter <br />regarding changes to the monitoring requirements in Part II, Section 1 of your Yankee Gulch <br />Site, EPA Area Permit C030858-00000 Rio Blanco County, Colorado. Your letter was a result <br />of our on-going discussions with American Soda regarding possible indicators for cavern and/or <br />instrumentation problems. American Soda undertook a complete review of their cavern <br />monitoring system. The purpose of this review was threefold: 1) to look at the possible causes of <br />a reported out-of-balance situation in cavity 20-26; 2) to evaluate the various monitoring <br />parameters and their relationship to potential cavity failure; and 3) to come up with a process and <br />criteria for determining if there may be a cavity failure. Additionally, a meeting between EPA <br />and American Soda representatives was held on January 29, 2003, to discuss the results of your <br />review of the data relating to possible cavity instability. Your letter and associated data <br />indicates the following general relationships between temperature, pressure, flow, and <br />concentration/density exist in the nahcolite solution mining wells during normal mining <br />operations:l) the inlet pressure increases as the concentration of nahcolite in the production fluid <br />Page 1 of 3 <br />~'a Printed on Recycled Paper <br />