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December 23, 1999 ~ • Page 3 ' A coaxial cable will be attached to the outside of the steel casing installed as part of a ' solution cavity well completion (Figure 2). The cable will be grouted in place in the drillhole by tremie placement of cement during well completion. ' Once installed, TDR waveforms will be collected according to the monitoring schedule in Section 3.3. Cable testing hardware will be connected to the coaxial cable installed in each well and ' data recorded. TDR waveform records will be cataloged for each well and compared to previous waveforms for detection of subsurface movement. ' The performance of the TDR monitoring will determine how TDR is incorporated into the long-range monitoring program. Future panels or mining areas may have TDR instrumentation in a limited number of wel Is. If TDR does not prove to be an adequate means of monitoring subsurface ' movement, other instrumentation techniques will be evaluated. 3.2 Borehole Geophysics ' Borehole geophysics logs will be nrn periodically at each well in service. A natural gamma log will be used to detect subsurface movement. 3.3 Solution Cavity Characterization American Soda will evaluate current technologies and methods to chazacterize the nahcolite ' solution cavity and present the findings to CDMG, BLM, and EPA. This task will be accomplished by June 2000. After selecting a viable technology(s), American Soda will test the selected ' technology(s) in a test phase cavity to verify that the approach will work during commercial mining operations. Results of the field testing will be reported to CDMG, BLM, and EPA. ' 3.4 Subsurface Monitoring Frequency and Duration TDR data will be collected monthly. Upon reclamation of a well field panel (or area), ' monitoring on an annual basis will continue until an adequate understanding of the data and the potential for subsidence is attained. At that point, American Soda could apply to the CDMG, BLM, ' and EPA for modification or termination of that monitoring. It should be noted that reclamation of those wells with TDR instrumentation will necessarily be delayed until completion ofthe subsidence ' monitoring. Borehole geophysics will be conducted four times for each well in service during the life of ' a well: (1) following initial drilling of the well, (2) after production of 85,000 tons from a well, (3) ' after production of 150,000 tons from a well, and (4) after retirement of the well. ' Agapito Associates, Inc.