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Aprrl !S, /999 • • pQge j <br />data recorded. TDR waveform records will be cataloged for each well and compazed to previous <br />waveforms for detection of subsurface movement. <br />The performance of the TDR monitoring will determine how TDR is incorporated into the <br />long-range monitoring program. Future panels or mining azeas may have TDR instrumentation in <br />a limited number of wells. If TDR does not prove to bean adequate means of monitoring subsurface <br />movement, other instrumentation techniques will be evaluated. <br />3.2 Borehole Geophysics <br />Borehole geophysics logs will be run periodically from the monitoring and instrumentation <br />string (Figure 2) at each well in service. A natural gamma log will be used to detect subsurface <br />movement. <br />33 Solution Cavity Charactcriration <br />American Soda will evaluate current technologies and methods to characterize the nahcolite <br />solution cavity and present the findings to the BLM. This task will be accomplished by June 2000. <br />If a technology or method emerges that has a high probability of success and helps achieve maximum <br />recovery of the resource, American Soda will test the technology or method. <br />The current mine plan anticipates initiating commercial mining in the fall of yeaz 2000. This <br />startup date will provide an opportunity to test a selected technology or method as the cavities <br />approach the anticipated radius of l00 ft. This opportunity should present itself between the year <br />2002 and 2003. <br />3.4 Subsurface Monitoring Frcqucncy and Duration <br />TDR data will be collected montltly for each well in service. Upon reclamation of a well <br />field panel (or azea), monitoring on an annual basis will continue for a period of five years. If <br />movement is detected, subsidence monitoring will continue for a period of five years following the <br />last detection of movement. <br />Borehole geophysics will be conducted four times for each well in service during the life of <br />a well: (1) following initial drilling of the well, (2) after production of 85,000 tons from a well, (3) <br />after production of i 50,000 tons from a well, and (4) aftcr retirement of the well. <br />Agapito Associates, Inc. <br />