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third year of the first five-year permit period. Data from this monitoring network is to be utilized to verify the design of the buffer zones proposed beneath the Dry Fork of Minnesota Creek and to predict the magnitude of subsidence and subsidence phenomena to be expected throughout the remainder of the lease property. Additional future subsidence monitoring networks shall also be proposed for the Dry Fork area to assure that subsidence impacts are prevented. As a portion of its November, 1984 permit revision application, WECC proposed a relocation of the originally required subsidence test panel and accompanying subsidence monitoring network. Reconfiguration of the underground mine plan, necessitated by an approved reorientation of the mains to avoid an area of bad coal and roof conditions, has resulted in a need to relocate the first panel to be subsided. The relocation is not significant, allowing the originally installed ground water monitoring wells to serve their original purpose, monitoring ground water response to subsidence of the test panel. However, the surface subsidence monument locations require amendment. The amended monitoring network is depicted in Figures 7, 8 and 9 of Appendix A to WECC's November, 1984 permit revision application. A row of monuments installed parallel to the axis of the test panel will be spaced on 100-foot centers. Two rows of monuments will transect the test panel and will be spaced on nominal 50-foot centers. These transverse monument rows will extend to the east of the panel centerline above the mains and to the west for at least 750 feet to the west of the panel centerline. WECC will tie the monitoring to a network of more permanent surveying triangulation bench marks to be established beyond the area of potential subsidence influence. Resurveying of triangulation monuments will be performed annually, to all crrelation of semi-annual aerial photogrammetric surveys discussed heraafter. WECC commits to two pre-subsidence field surveys of all monitoring points and annual resurvey of triangulation monuments with Second Order Class II horizontal accuracy. WECC commits to achieving vertical error no greater than + 0.2 feet. WECC will compare these field survey results with the results of a aerial photogrammetric survey of the monument grid. In order to avoid misunderstanding the Division has imposed a stipulation defining the accuracy standards to be achieved in completing both the field and aerial photogrammetric pre-subsidence surveys. Further, the Division believes the photogrammetric subsidence monitoring technique to represent an interesting potential technical innovation. However, the technique is unproven for the completion of subsidence monitoring surveys. Therefore, the Division believes it prudent to require the applicant to correlate its aerial photogrammetric monument surveys to traditional ground survey monitoring of selected triangulation monuments. In order to avoid misunderstanding, the Division has imposed a stipulation defining the accuracy standards to be achieved in completing post-subsidence aerial photogrammetric surveys of the subsidence monumentation grid.