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CHAPTERTWO Proposed Action and Altematiues American Soda's monitoring program is anticipated to include the following elements: • Mechanical integrity testing (MIT) of each well would be performed prior to operation. Mechanical integrity would be demonstrated by a combination of methods, including cementing records, pressure testing, and cement bond logs. After the initial :~fIT, additional MITs would be conducted, as necessary (or once every 5 yeazs as required ir.. 40 CFR 146.33b for Class III wells) during the life of the solution mining wells. • Volumetric flow meters and density meters would be installed to monitor the: production and injection fluid flow lines. Amass balance would be performed on each well to demonstrate that fluids have not migrated from the solution mining cavity and to determi~te cavity volume. • Pressure recording devices would be installed at each wellhead to continuously record the gas pressure within each well. • Inlet and dischazge temperatures and pressures would be measured continuously in the injection fluid and production fluid flow lines for process control and for correlation with fluid density measurements. • Injection fluid and production fluid pipelines would be sampled on an as-needed basis. Injection fluid samples would be collected from the pipeline immediately up:~tream of where the pipeline branches to feed all solution mining wells, and production fluid ~xould be sampled at each solution mining well. Some samples would be preserved for off-site analysis by an analytical laboratory, and others would be analyzed onsite. Onsite chemical analyses would likely include sodium bicazbonate, sodium carbonate, sodium chloride, pH, and specific gravity. Samples sent to off-site laboratories would be analyzed for the actual composition of the fluid for correlation/calibrntion of the density measurements and for process evaluations. Pertinent solution mining well monitoring data would be provided in monthly reports to the BLM. 2.2.5.2 Subsidence Monitoring Monitoring of potential subsidence would be performed throughout the operatin€; life of the Yankee Gulch Project to verify the results of thermomechanical studies used to develop the Commercial Mine Plan. If subsidence effects aze substantially greater than expected, the mining strategy would be adjusted. Following is a description of the proposed monitoring program. • Several benchmarks would be established outside the mining azea, and their elevations would be measured and recorded prior to commencement of commercial operations. Brass markers would be installed on the well pads of several solution mining wells in each 5-yeaz mining panel. The wells would generally be situated along a northwe<.;t-southeast line through the center of the panel, with additional wells located azound the periphery of the panel. The exact location and number of wells would be determined in consultation with the BLM, CDMG, and EPA. The brass marker elevations would be measured relative to benchmark elevations once every 6 months during commercial operations. 2-20 LJ