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Subsidence monitoring and evaluation will be preformed before, during, and following <br />the experimental mining activity. AmerAlia expects to monitor and control the mining <br />process closely to avoid significant subsidence impacts. <br />2.0 Subsurface Monitoring (top of cavity to surface) <br />The purpose of subsurface monitoring is to ascertain movement of strata overlying the <br />solution cavities. <br />Near welibore roof fall, or differential strata movement overlying the cavity and below <br />the dissolution surface, is expected to damage the casing and cement and disrupt the <br />gamma log. Should this occur, it will likely be rapidly detected by routine process <br />monitoring of solution flow, pressure and assay. In any case, such subsidence damage <br />and disruption will be measured by regular wireline logging of the wellbore. <br />The initial roof fall indicator is expected to be increased salt (NaCl) in the process <br />solution. Should any portion of the mining cavity advance vertically into the lower salt <br />zone, salt will leach rapidly (and preferentially to nahcolite) and will cause process <br />contamination. Mining in that cavity will be discontinued when salt contamination <br />reaches unacceptable levels. <br />Any advanced subsidence, which damages the casing and cement bond, in the aquifer <br />strata above the Dissolution Surface will be rapidly detected by the fluid pad pressure and <br />volume loss process monitoring system. This system will automatically record loss in <br />fluid pad pressure and automatically indicate these losses through alarms. Increased fluid <br />pad volume loss is measured and recorded daily. <br />Wireline natural gamma logging and comparison to baseline will be conducted as <br />indicated by unusual operating results or when single cavity production has reached the <br />experimental test mining goal of approximately 75,000 tons. The results will be used to <br />develop a phase II subsidence monitoring plan, if mining of the cavity is advanced. <br />