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In a continuing effort to develop a viable use of TDR monitoring, American Soda <br />will conduct feasibility study of installing TDR after mining is completed in a <br />cavity. The test program will install TDR in we1120-12. <br />TDR is an electrical pulse-testing technique originally developed by the <br />telecommunications industry for locating faults in coaxial power transmission <br />cables (Dowding et al. 1988). A cable tester is used to create a voltage pulse in <br />the cable. When faults, crimps, or elongations are encountered in the cable, a <br />reflected signal returns to the cable tester as a result of the change in electrical <br />wire properties. Knowledge of the properties of the wire permit location of cable <br />damage by measurement of travel times. <br />TDR will be installed in we1120-12 by establishing a base plug in the well bore. <br />A 2-3/8-inch diameter tubing string, with a 7/8-inch coaxial cable strapped to the <br />tubing, will be installed within a 7-inch casing from the base plug to surface. The <br />tubing will be cemented in place with circulation to surface. Cmce installed, TDR <br />waveforms will be collected according to the monitoring schedule in Section 3.4. <br />The performance of the TDR monitoring in we1120-12 will determine how future <br />TDR installations are incorporated into the long-range monitoring program. To <br />be considered for any future installations, the test TDR installation must meet the <br />following minimum criteria. <br />+ The we1120-12 TDR installation must be able to be placed in service <br />(intact and operable) in the existing wellbore using standard installation <br />and completion techniques. <br />+ Once installed; the TDR equipment must operate continuously and <br />remain in service for a minimum of 3 years. <br />+ Monitoring results must be sufficient to clearly show resolution of the <br />crimping pattern. If the demarcation of the crimping within the coaxial <br />cable cannot be clearly demonstrated over a minimum of three years, the <br />technology will not be considered suitable for further deployment. <br />If TDR is determined to be viable and produces data reasonably useful and <br />definitive in evaluating subsidence, future panels or mining areas may include <br />TDR instrumentation installations on a limited number of wells. In future mining <br />panels, up to six wells in a mining panel maybe equipped with TDR. <br />If TDR does not prove to be an adequate means of monitoring subsurface <br />movement, the agencies (EPA, BLM, and CDMG) may request that other <br />instrumentation techniques maybe evaluated. <br />3.2 Borehole Geophysics <br />FINAL: Modification No. 9, UIC Area Permit No. C030858-00000 <br />Page 44 of 46 <br />