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over approximately 400 feet of overburden. Advance <br />• development of this subanain occurred in September, 1987. <br />Surveys were initiated on an annual basis in 1988 oral have <br />continued to date. No subsidence is evidenced by the 1992 <br />survey data at this location with an elevation gain of 0.05 <br />feet being measured. <br />Station 95: Station 95 is located over Panel Z and overlies approximately <br />1500 feet of overburden. Panel Z is scheduled to be mined in <br />1994. Survey coordinates were established for the first time <br />at station 95 in 1992. <br />Pitkin Mesa Pipeline Subsidence Monitorira Summary <br />Seven subsidence monitoring stations were established at locations along the <br />Pitkin Mesa Pipeline which overlies Panel C. Panel C development oon¢ne~ in <br />October with twenty four crosscuts ca~leted by January 1, 1993. Panel C was <br />mined utilizing a partial extraction design intended to preclude the development <br />of subsidence in order to protect the pipeline. The subsidence monitoring <br />stations along the pipeline are depicted on Map No. 2-5A, Permit No. C-81-038. <br />The stations were surveyed twice in 1992; January 27 and September 26. Both <br />surveys were conducted prior to mining. Summary sheets are appealed. Surveys <br />will continue approximately semi-annually until stability is doc~unented. <br />Visual Monitoring 1992 <br />• Visual subsidence monitoring is accomplished by periodic "~ralkovers" of <br />recently mined areas within the present permit area. Walkovers are <br />generally done in conjunction with survey monitoring due to the seasonal <br />accessibility of the area. Visual monitoring is concentrated over areas <br />of retreat mining with particular emphasis on areas mined under low <br />overburden. <br />A visual subsidence monitoring inspection was conducted in September of <br />1992. Panels A and A+ were inspected. Panel A advance was Meted in <br />April, 1991. Retreat mining was completed in December, 1991. Panel A+ <br />advance was completed in February, 1992. Retreat mining was completed in <br />mid-March, 1992. <br />No visual indications of subsidence were noted during the subsidence <br />inspection. No visual indications of subsidence were noted during <br />surveying or hydrology monitoring efforts for the 1992 calendar year. <br />Projected Subsidence facts 1993 <br />Subsidence impacts during 1993 are projected to be minimal based upon <br />subsidence patterns established to date. Mining during 1993 is projected <br />to occur in panels C, Y, and AA. Development and retreat mining is <br />scheduled to occur in panels C, and Y, and development mining only is <br />• scheduled for panel AA. The areas scheduled to be mined during 1993 are <br />not significantly different from areas previously mined in terms of <br />topography, geology, or mining technique and should not, therefore, <br />5 <br />