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<br />Thermal expansion and contraction of the well casing to which the surface subsidence <br />monument is attached could cause erroneous measurements of as much as 2 inches in the <br />perceived elevation of the ground surface at the well. Such aberrations would lead to <br />misinterpretationofsubsfdence data. As reported, subsidence magnitudes from modeling <br />of realistic scenarios are expected to range from 0 to 0.7=1 foot (Agapito 1999a). Temperature <br />changes in the casing will be most dramatic when injection into a well ceases. Conceivably, <br />the temperature of the well casing at the ground surface could change from 420° F to below <br />freezing once the injection of hot water ceases, and the temperature of the well casing at <br />a depth of, say, 20 feet could change from 420° F to approximately 50° F (the ambient <br />underground temperature). Assuming that the casing can move up and down where it is <br />grouted into soil and that the length of pipe in the soil zone including stick-up is <br />approximately 23 feet, the calculated vertical movement may be 0.7 inch (Agapito 1999b). <br />Monitoring points for future mining panels will be established based on the outcome of <br />monitoring of the 0-5 year mining panel and on consultation with the regulatory agencies. <br />References <br />Agapito (Agapito Associates, Inc.). 1999x. Surface Subsidence- Realistic Scenarios. Letter <br />Report from Agapito Associates, Inc. to Steigers Corporation. January 7. <br />Agapito (Agapito Associates, Inc.). 1999b. Subsidence -Technical Revision for DMG 112 <br />Permit. Letter Report from Agapito Associates, Inc. to Steigers Corporation. July <br />29. <br />BLM (U.S. Bureau of Land Management). 1999. Final Em~ironmental Impact Statement <br />Yankee Gulch Sodium Minerals Project American Soda, L.L.P. July. <br />