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~,',Fnsc„~. UNITED STATES ENVIRONMENTAL PROTECTION AGENCY _~~ ~ REGION 8 ~1~~1/f`J $ 999 18'" STREET -SUITE 300 DENVER, CO 60202-2466 http://www.epa.gov/reg I on08 Ref: 8ENF-UFO AU6 31 2004 RECEIVED SEP 0 12004 Oivisian of Minerals and Geology CERTIFIED MAIL 7003-2260-0001-7778-9333 RETURN RECEIPT REQUESTED Mr.. Ed Cooley ~ b1 erican Soda, LLP X2717 County Road 215 Pazachute, CO 81635 Deaz Mr. Cooley: Jf'1-l ~(9~t-C;O~. Re: Underground Injection Control (UIC) TDR Subsidence Monitoring We1120-12 '~ EPA Permit # C030858-04552 Rio Blanco County, Colorado EPA's UIC program staff have reviewed your July 28, 2004, letter in which you included three measurement events using the 7/8 inch Time Domain Reflectometry (TDR) subsidence monitoring cable installed inside the 2-7/8 inch tubing, now cemented to the 7 inch long string casing in the above described well. The TDR cable was purposefully crimped at every other tubing joint (about 60 feet). A total of 1404 feet of tubing was installed in the well. On June 17, 2004, the 2-7/8 inch tubing was cemented to the 7 inch long string casing. The tubing was left open for future temperature logging. The monitoring events referenced in your letter aze re-typed here for clarity. Event 1: June 17, 2004 -prior to cementing the 2-7/8 inch tubing in the 7 inch long string casing, Event 2: June 17, 2004 -immediately after cementing the 2-7/8 inch tubing in the 7 inch long string casing, and Event 3: July 1, 2004 -are-test of the June 17, 2004 monitoring event, after allowing the cement to cure. In the July 28, 2004, letter, American Soda, LLP (AS) points out that the monitoring from Event 1 showed signal returns from as deep as 1209 feet, which correlates well with the depth of a crimp placed in the TDR cable. The monitoring from Events 2 and 3, however, only show signal retums from as deep as 1000 feet, and the nearest crimp in the cable is at 1015 feet. Printed on RacyGed Paper