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<br />Continuous monitoring of flow rates and densities will <br />provide an ongoing material balance, which will allow <br />calculations of the mass of nahcolite extracted. The <br />records of ongoing material balance shall be maintained <br />at the site and may be reviewed during inspections. <br />This data will be utilized in review of the applicant's <br />compliance with their Permit. <br />The applicant has prepared the Subsidence Monitoring <br />Plan dated April, 1999, which was submitted to the BLM, <br />Colorado Division of Minerals and Geology (CDMG) and <br />the EPA. The 4`" revision of this plan, dated <br />December 23, 1999, is incorporated into this Permit as <br />Appendix I. As provided in this plan, the Permittee <br />must establish surface monitoring monuments on the <br />initial 25 wells in addition to the grid of land <br />surface monuments. The subsurface monitoring plan <br />includes the installation of coaxial cable in solution <br />mining well bores for use of Time Domain Reflectometry <br />(TDR), which is technology used to detect differential <br />movement close to the top of the cavity and above. If <br />subsurface movement occurs, the coaxial cable will <br />break or stretch. The location of the change in <br />coaxial cable properties will be determined by use of a <br />cable tester. Borehole geophysical logs will also be <br />run periodically to substantiate the TDR monitoring <br />results, and corrective action implemented if <br />necessary. The shape of the cavity is, of course, an <br />important element that affects subsidence. For that <br />reason, the Permittee is required to undertake studies <br />and evaluate techniques for assessing cavity shape. <br />Depending on the results of these studies, American <br />Soda may be required to establish additional monitoring <br />wells to better track cavity influence on the pillars. <br />This monitoring will provide additional information <br />regarding the potential for cavity problems. This <br />Permit requires submittal of the subsidence monitoring <br />results. If the subsidence monitoring indicates that <br />there is significant subsidence, additional monitoring <br />or other corrective actions could be initiated. <br />The injection fluid and production fluid pipelines <br />shall be equipped with sampling ports to facilitate <br />periodic collection of samples for chemical analysis. <br />Injection fluid samples shall be collected from the <br />pipeline immediately upstream of where the pipeline <br />EPA FINAL Area Permit No. C03858-00000 <br />Page 12 of 164 <br />