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Mr. Ed. Baker April 18, 2003 Page 2 During caving above a cavern, both sheazing and extension aze expected. The zone of deformation above the cavern will grade from areas where roof fallouts occur with block rotation, to areas where minor cracking or bed sepazations occur, to azeas where deformation, without damage or impact to the hydraulic conductivity, of the overlying rock is unchanged. The TDR technology has been used to detect the area where joint opening and block rotations occur, commonly referred to as the cave zone. Reference crimps will be made in the cable during installation to increase the accuracy of depth determination. Without reference crimps, the resolution of location of the localized deformation causing the spike is about t 2% of the cable length. Using reference crimps, the distance to a spike can be graphically scaled between the signals returned by the crimps and, assuming that the location of the crimps is known and is unchanged, the depth of the spike, caused by localized rock deformation, can be determined. An additional method is available to determine absolute deformation of the TDR. The reflection time from crimps, and the cable end to the surface, is an absolute measure of distance. The change in reflectance time from crimps and the cable end will be monitored to detect a measure of absolute deformation from the surface. The accuracy of this method and the threshold of detection aze not known at this time. The length of the cable influences the sensitivity of the TDR cable. At shallow depths a smaller localized deformation of the cable can be detected. Crimps and sheazing of the cable will be evident in the TDR signal at the depths proposed for the Natural Soda application. The exact threshold of detection for a localized shear deformation of the cable is unknown, but is expected to be less than half of the deformation to cause complete shearing of the cable, or approximately 0.3 to 0.4 inches. For extensional necking of the cable, a signal deviation is expected at a localized extension of approximately 0.4 inches. The accuracy of the depth of the signal modification or localized deformation will be approximately 0.5 ft. Four TDR cables aze being installed at distances of approximately 55 ft, 75 ft, 95 ft, and 115 ft above the Dissolution Surface. The contact between the L-5 and the R-6 is approximately 113 ft above the Dissolution Surface so that the lowest three cables will be anchored in the L-5 zone, with the fourth cable 2 ft above the L-5/R-6 contact. The TDR cable ends will be fitted with end caps to prevent water from intruding the dielectric. If a cable breaks or the sheathing is punctured, water will intrude the dielectric. The water intrusion saturates the dielectric between the cable and sheathing, and renders the cable ineffective. This response is the reasoning behind the use of four cables at staggered depths. If the lowest cable undergoes deformation due to caving (subsidence), such that the cable is compromised, and the second lowest cable is functioning, the cave will have extended 20 ft or less from the bottom of the lowest cable, and will be located somewhere between the original depths of the two cable ends. The frequency of monitoring should allow for TDR signal changes to be detected before the failure or puncturing of a cable, and hence, detection of the depth of the localized deformation. Associates, Inc.