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Jirne 20, 2000 <br />1. 0 INTRODUCTION <br />Pu,~~e 1 <br />"this report presents and evaluates current technologies and methods useful for <br />characterization ofthe eavitiesdeveloped during solution mining on the Yankee Gulch Lease during <br />commercial nahcolite mining by American Soda L.L.P. (American Soda). Possible technologies are <br />critiqued on their probability of success, resolution, and cost effectiveness. A recommendation of <br />the technologies best suited for defining the solution cavity boundaries is given. <br />The need for this review of technologies is specified in the Pinal Environmental Impact <br />Statement (PSIS) written by the Bureau of Land Management (BLM) (1999), as well as in the <br />Subsidence Monitoring Plan (Revision 4). In the later document, American Soda has been asked to <br />"evaluate current technologies to characterize the nahcolite solution cavity and present the findings <br />to the CDMG (Colorado Division of Minerals and Geology), BLM, and EPA (Environmental <br />Protection Agency). This task will be accomplished by June 2000. After selecting a viable <br />technology(s), American Soda will test the selected technology(s) in a test phase cavity to verify that <br />the approach will work during commercial mining operations. Results of the field testing will be <br />reported to the CDMG, BLM, and EPA" It is interpreted from this language that the CDMG, BLM, <br />and EPA expect the selected technology will be demonstrated on a test cavern before the start of <br />conunercial solution mining operations. <br />The cavern shape technologies considered are in addition to the Time Domain Rellectometry <br />(TDR) and borehole geophysics designed and included in the subsidence monitoring program. "these <br />two techniques provide information on the integrity of the "crown pillar" between the top of the <br />cavern and the dissolution surface. <br />Candidate technologies worthy of further review were established in a meeting between <br />Agapito Associates, Ina (AA[) and American Soda on April 19, 2000. These technologies are: <br />volumetric analysis, 3D seismic, vertical seismic profiling, cross-hole seismic, magnetotellurics, <br />exploration drilling, magnetics, and tiitmeters. Information on these technologies has been collected <br />from texts, reference materials, Internet sites, and discussions with vendors and consultants. The <br />report first summarizes the findings of the study, gives recommendations, and, finally, discusses the <br />merits and drawbacks of the various technologies. <br />This report provides a relative ranking of the technologies in order of most suitable to least <br />suitable. Ranking of the technologies is based upon several considerations. First, the probability <br />Agapito Associates, Inc. <br />