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decrease the frequency depending on the results <br />of the monitoring. <br />Cavity development shall be monitored to estimate <br />cavity size. The leached solution cavity will be a matrix <br />of oil shale rather than a void, and its size and shape <br />must be determined by indirect methods. Periodic <br />monitoring of flow rates and densities will provide an <br />ongoing material balance, and lead to estimates of cavity <br />configuration which shall be submitted quarterly to the <br />EPA. Methods that characterize the solution. mining cavity <br />have the potential to improve the mining technology. <br />If changes in the individual cavity conditions or <br />operating parameters such as mass balance, injection and <br />production volumes, or solution well temperature or <br />pressure, indicate that downhole problems representing <br />potential endangerment to a IISDW may occur, the cavity <br />shall be shut-in and the permittee will notify EPA as <br />provided by Part III Section E.10.(c) of this permit. The <br />permittee shall also immediately begin developing a <br />response action to address the problem. This plan will be <br />provided to EPA within five days of the time that the <br />operator became aware of the problem. <br />The operator shall evaluate the production and <br />injection monitoring data relating to potential operational <br />failure of a cavity with the objective of developing <br />failure criteria for this packerless system of solution <br />mining during the first year of operation. A report <br />outlining the recommended failure criteria and associated <br />response actions shall be included in the quarterly report <br />following one year of operations. <br />A subsidence report shall be submitted to the EPA <br />annually, which contains borehole geophysical data and <br />annual surface monument measurements. The subsidence <br />report shall include a map of surface monument locations, <br />locations of wells where borehole geophysics was conducted, <br />monument coordinates and elevations, and a summary of <br />pertinent observations during the reporting period. <br />Surface monuments shall be established at each production <br />and pillar well. Borehole geophysical data shall include <br />natural gamma ray wireline logging after 75,000 tons of <br />nahcolite production from each single solution mining well, <br />to be compared with pre-production counterparts; <br />thereafter, while in operation, each cavity shall be logged <br />annually. The logs and a narrative describing the results <br />shall be included in the annual report. <br />Page 17 of 120 <br />EPA FINAL Area Permit No. CO3870-00000 <br />