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On the north-south leg of the powerline, two structures and possibly a third were expected to be affected by longwall subsidence. One structure overlies room-and-pillar area 2 (RP-2). Two sVuctures are within the outline of longwall panels 1 and 2 (LW-1 and LW-2) and initial tilting toward the southwest was expected as the subsidence wave passed them. As subsidence is completed they were expected to return to a vertical or near vertical orientation. The third structure was on the edge of the subsidence. The three structures over the longwall panels, as discussed above, were to be affected in 1987, 1988 and 1989. No tilting of the structures due to longwall mining was observed during active subsidence. I.A.6.h Subsidence Monitoring Program. A program was designed to yield subsidence data that would be used to verily the accuracy of initial predictions under actual ground conditions, and which could be used to predict future effects after monitoring the first longwall and the first room and pillar panel. BME monitored subsidence over the first longwall panel (LW1) using state-of-the-art analytical photogrammetry. LW1 was mined in calendaryear 1987 and the first two months in 1988. Four flights were flown to record and monitor the surface over LW1. The first flight was flown during August, 1986 to establish baseline conditions and base drawings for both LW1 and RP5 for comparison with the future flights. The second and third flights occurred in May 1987 and September 1987. Data and drawings from these flights were presented to Colorado Mined Land Reclamation Division (CMLRD), now DMG, in a report in December, 1987 for review. The fourth flight occurred in June, 1988. The fourth flight information and drawings were assembled into a final report and presented to DMG in October, 1988. Residual subsidence may occur after June, 1988, above panel LW1. It is important, for purposes of verifying the accuracy of subsidence projections contained within the permit document, to accurately document the magnitude of subsidencewhich occurs above this test panel. Conventional semi-annual survey monitoring of the five control points located within the zone of subsidence (see description below) continued until cessation of subsidence was accurately documented. In the event that any of these conventional survey monuments experienced more than 1.0 foot of residual subsidence, an additional aerial photographic flight, subsidence map and report would have been prepared for presentation to DMG within one year following cessation of subsidence. This reporting is no longer be required. I.A.7 Mine Ventilation A permanentfan has been installed at the D-Portal ventilation slope. This fan operates in a blowing configuration pushing fresh air into the mine from the Ventilation Entries and Rio Blanco County Special Use Permit #81-1 EahibitB -Mining Plan September2000 13