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-60- a network of more permanent surveying triangulation bench marks tc 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 hereafter. 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 far 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. Subsequent to the original submission of exhibit 3.4.8.A, the Division addressed additional concerns to WECC regarding the possible effects of subsidence upon landslide deposits neighboring Beaver and Minnesota Reservoirs. WECC responded in letter form indicating that it desires that the final designation of possible additional "safe areas" of limited extraction be tied to the detailed results of the analysis being performed upon the landslide deposit above the Town of Somerset. The Division finds that the following stipulations are necessary for a finding of compliance with subsidence related requirements of Rule 2.05.6(6) and 4.20. Stipulation No. l7 THE DIVISION DIRECTS WECC TO COMPLETE THE INSTALLATIOtI OF THE SUBSIDENCE MONITORING NETWORK PRIOR TO THE INITIATION OF EXTRACTION OF COAL WITHIN THE PANEL DESIGNATED IN APPENDIX A TO THE NOVEMBER, 1984 PERMIT REVISION APPLICATION ENTITLED "APPLICATION TO REVISE THE MINING AND RECLAh1ATI0N PLAN FOR THE MT. GUNNISON N0. 1 UNDERGROUND MINE". THIS MONITORING NETWORK IS DESIGNED TO MONITOR THE FIRST PANEL WEST FROM THE SW MAINS INTAKES AND SOUTH OF THE N0. 1 WEST SUBMAINS, DESIGNATED AS "PANEL 1W-1S", LOCATED ADJACENT TO AND PARALLEL TO THE WESTERN BOUNDARY OF SECTION 21, RANGE 90W, TOWNSHIP 135. THIS MONITORING NETWORK SHALL CONSIST OF SUBSTANTIAL MONUMENTS DESIGNED TO RESIST FROST-HEAVE, FIRE, AND THE ACTIONS OF CATTLE AND WILDLIFE.