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11/14/2006 15:11 9709295595 WEST ELK PAGE 02 West Llk one The "worst possible consequences" from mining to hydrologic resources, hydrology monitoring stations, and the many trails and unimproved U.S. Forest Service roads could be cotzlplete loss of surface water resources to the mine workings, total deswction of the stations and total destruction or blockage o£ the trails on roads. MCC will repair or replace these items as discussed later in this section. Subsidence MoxitorinQ Plan - 2.OS.6 (6)(6)(ii), (6)(c)(i) and f6)(e)(iii) A)Subsrdex eMonitorinr Until 1999, subsidence monitoring at West Elk Mine was accomplished using conventional survey methods of a monument grid. 'The grid was ]aid out over the first three longwall panels to be mined (panels 1-3NW), and successfully verified MCC's prediction about the amount of subsidence. The grid is shown on Map 24. As subsidence of the three longwal] panels was completed and the surveys no longer showed movement, monitoring of the grid was discontinued in 1999, However, the monuments have remained in place to be surveyed in the event that any unanticipated ground surface displacement occurs in the vicinity of the monuments. In the jumbo Mountain permit revision application (PROS), MCC proposed measuring subsidence using aerial photogrammetric methods. MCC had been collecting data from aerial flights since 1995, Areas were flown prior to, during, and fallowing mining. MCC has evaluated this data and determined that measuring subsidence using aerial methods is not feasible for a number of reasons. The first is the rugged topography of the areas that are undemtined makes it difficult to place survey panels and interpret the data. in addition, placing an adequate number of survey panels has also been diicult due to limited access and thick vegetation. Another difficulty, pattieulariy on Jumbo Mountain, is that it is difficult to distinguish between actual subsidence and ground movement due to landsliding. For Panel 25, MCC will install six (6) reflectors or monuments pieced ott Sylvester Gulch to determine subsidence. These stations are depicted on Map 53B. These stations will be surveyed prior to commencement of lOngwall mining in Panel 25. and then when longwall mining commences they will be surveyed monthly and reported quarterly and semi-annually. The tnonthly surveys will continue for two months following completion of longwall mining in pane125. The monitoring of MCC's subsidence grid established the amount of subsidence that occurs over a longwall panel, when. it occurs, where ifoccws, and when it is complete; therefore, there is na longer a need for additional grids. instead, MCC will visually inspect the ground over the areas that have been undermined to document any disturbance that may have occurred. MCC will also visit new mine areas prior to any subsidence occurrence to document pre-existing conditions, and will also visit locations where cracks have previously been documented to verify that the cracks are healing. MCC will utilize traditional survey methods, as necessary, to evaluate structures of concern, for example, Dry Fork. Also, MCG will conduct subsidence monitoring of the following: Dry Fork thalwegs, roads, well casings, inverts of culverts, flumes, monuments at stock ponds, and buildings, Monument Dam, and Minnesota Reservoir, Specific subsidence monitoring measures and plans will include the verification of the subsidence angle-of--draw in the SOD area. The monuments established as part of the baseline survey will be resurveyed at least three months but no more than. nine months after the longwall face has moved past the end of the longitudinal siuVCy line to dctermute the amount of subsidence t1,at has occurred and the angle of draw of subsidence. A report detailing the angle of 1.05-162 R¢vixed Jum TORS PR1 Q R¢v. Morch 2006: Moy 2(tOfi PRT 0, Nov. 2006TR107