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AGAPITO ASSOCIATES, INC. <br />CONSULTING ENGINEERS <br />RECEIVED GRAND JUNCTION OFFICE <br />April 18, 2003 Ap{~ 2 4 ~Q~3 134-24 <br />Division ~f Minerals and Geology <br />Ed Baker <br />Natural Soda, Inc. <br />3200 County Road #31 <br />Rifle, CO 81650 <br />RE: WRN -EPA Questions dated April 17, 2003 <br />Deaz Ed: <br />As per your request that we respond to questions 6 and 7 in the March 17, 2003, letter <br />addressed to you by Edwin Hogle, Director of the Ground Water Program, United States <br />Environmental Protection Agency, Region 8. Included, as an attachment to this letter, is a figure <br />showing the completion details of the planned Subsidence Monitoring Well. <br />Q 6.1: How much subsidence can be reliably measured at various depths of interest? <br />A: Testing of cable in shear and extension (Dowding, Su, and O'Connor 1989)1 indicates <br />that, for the 0.875-inch-diameter cable, localized shear will become evident at about <br />0.3 inches of sheaz deformation, and the outer conductor will fail (cable compromised) at <br />about 0.8 inches of deformation. Tests on extensional behavior indicate there may not be <br />a reflection until failure of the outer conductor, especially for the 0.875-inch cable. <br />According to the above-referenced study, extensional failure of the 0.875-inch cable <br />occurred at about 0.5 inches. <br />Localized cable deformation is recorded by the TDR monitoring device as a spike in the <br />signal. Two types of localized cable deformation aze recognized: sheazing and <br />elongation. Localized sheaz deformation produces a distinctive spike, which grows in <br />amplitude as the degree of deformation increases. Localized elongation produces a less <br />distinct perturbation in the return signal, and this signal is more difficult to detect. <br />Tensional yield and necking of the cable just prior to sepazation of the cable produces a <br />distinct perturbation in the return signal. At sepazation it is expected that water intrusion <br />into the dielectric and saturation up to the static water level will render that particular <br />cable useless. <br />i Dowding, C. H, M. B. Su, and K. O'Conner (1988), "Principles of Time Domain Reflectometry Applied to <br />Measurement of Rock Mass Deformation," International Journal of Rock Mechanics and Mining Sciences <br />& Geomechanics Abstracts, October, pp. 287-297. <br />GEOENGINEERING MINING ENGINEERING CR'IL ENGINEERING <br />715 Norizon Drive, Suite 340, Grand Junction, CO 81506 Ph: (970) 242-4220 FAX 245-9234 E-mail: ,AA/(a~apayito.com <br />2 East 22nd Street, Suite 307, Lombard, IL 60148-6106 Ph: (630) 792-1520 FAX 792-1580 E-mail: Frankataeapito(a)voLcom <br />