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3.1.3 TDR Well <br /> The 4A-5M well, south of the plant (Area P1) and containing TDR cables, is currently in use. <br /> Data from these cables will be collected monthly by NS, and quarterly by a third party, during <br /> active mining and for three years after cessation of mining within the areas, or until the cables <br /> become comprised (via water infiltration, etc.). If ground movement of six inches or more is <br /> detected the EPA, BLM, and DRMS will be notified, and mining in the area of the monitor well <br /> will stop until regulatory agencies approve alternatives. The TDR cables installed at the depths <br /> required for subsurface monitoring at the NS location have not proven to be durable; NS no <br /> longer constructs TDR style wells. <br /> 3.2 Surface Subsidence <br /> The purpose of the surface subsidence monitoring is to determine if there is any surface <br /> movement resulting from solution mining. No significant surface subsidence is anticipated. <br /> The surface monitoring plan has been designed to ascertain surface subsidence over the <br /> solution-mined cavities. Surface Subsidence Monuments are constructed by installing a section <br /> of rebar to approximately 3 feet below the ground surface and/or into bedrock when <br /> encountered. The monuments shall be generally located vertically above proposed or existing <br /> mining intervals on undisturbed ground. The coordinates and elevation of each monument are <br /> surveyed and recorded upon installation. A surface subsidence control point, at the Natural <br /> Soda plant, and additional monuments are located and are used to relate historic and newly <br /> collected data. Data collected from the Surface Subsidence Monuments and monitoring are <br /> included in the annual report. The accuracy of the surveys for the surface monument <br /> elevations will be commensurate with the equipment standards in use by professional <br /> surveyors, typically within ± 0.5 feet. To date, historical data has shown a typical survey <br /> variance of± 0.2 feet. If a deviation greater than 0.2 feet occurs the EPA, BLM, and DRMS will <br /> be notified within 10 days of discovery along with an action plan. <br /> 3.3 Solution Mining Interval Configuration <br /> Solution Mining Interval growth, size, and geometry will be monitored throughout the <br /> operating life of the wells by conducting a weekly mass balance calculation of interval volume <br /> based on daily measurement of injection/recovery fluid parameters; flow, temperature, and <br /> density. Additionally, solution mining interval parameters will be monitored by a mass balance <br /> leaching simulation model with volume calculation, to predict solution mined interval spatial <br /> development with respect to shape and size. <br /> Daub&Associates, Inc. Page 15 Natural Soda LLC 2022 EMP <br />