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Mountain Coal Company West Elk Mine Semi-annual Subsidence Report The most current subsidence survey for the West Elk Mine was performed in July 1993. The survey was completed by Messenger and Associates. The survey was conducted using radial and level loop survey methods. The instruments used were a Wild, T-l, theodolite; a Nikon , ND 20, distance meter; and an unspecified level. Several subsidence points have been destroyed. Number 63 was apparently destroyed by bears, Number 68 was reset after it had also been destroyed by bears, but now is bent. Number 96 had been bent by a vehicle and does not provide reliable data. When plywood panels were used to help locate the subsidence points in the field, an unusual circumstance occurred. The panels fostered a habitat conducive to ants, and their piles were constructed beneath the plywood panels. The ant piles were then apparently subjected to grubbing bears which tore the plywood panels and bent or destroyed the subsidence monitoring points. This explanation should resolve the concerns of the Division regarding the resetting of subsidence points 2, 3, I5, 36, 82, and 93. The plywood panels have since been removed from the other points in the field. It should be noted even though the points have either been destroyed or reset, the original spacing was close enough that there are many other points along the profile lines to maintain the the accuracy of the subsidence survey. The following tables reflect the northings, eastings, average pre-mining elevations, the previous report elevations (October 1992), the current survey elevations, subsidence since the October 1992 report and total subsidence. Additionally, though not required for the semi-annual subsidence monitoring report, the new subsidence profiles are being submitted with this report For review prior to the annual subsidence report which is due in April of 1994. The following tables indicate that the maximum total subsidence to-date is 7.54 feet and occurs over both the F and B Seams at point Nos. 40 and 41. The visual etTects of subsidence were limited to surficial cracks over the F- Seam No. 1 West, No. 1 South, Room and Pillar Panel and over the first B-Seam longwall panel. The cracks were northwest/southeast trending and were located directly over, or centered over, the panels. The cracks were various widths, from approximately two inches to 16 inches, the lengths of which were discontinuous, but did not exceed 100 yards in any length of run. Displacement at or near the cracks was not perceptible Mining advance was limited to the B Seam development in the B-West Ivtains, and the Third and Fourth Northwest Headgates The longwall retreat in the B No. 1 Northwest Longwall Panel (B 1 NWLW Panel) was completed and was set-up and retreat begun in the B2 N~'r`LW Panel in April of 1993.