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y ;'~ Mr. Jim Ferguson April 9, 1990 Page 3 such as those shaded on the map, may be left intact for ventilation or roof stability purposes. A subsidence monument will be constructed on the ground surface this summer, over the middle of the NW1S panel. The monument will probably be surveyed twice before the panel is retreat mined and then surveyed once each year until no change attributable to subsidence is detected. At the same time the subsidence surveys are performed, the three nest trees (or any other nest trees which may later be located within the affected area) will be visually checked. Should a nest tree be affected, the BLM will be notified. WECC plans to begin developing the Northwest Submains in mid- April, 1990, and should be at the southern extent of the NW15 panel and ready to begin retreat mining by the end of October, 1990. Assuming this schedule remains intact, the area of the panel which may affect the nests would be retreat mined and subsidence begun by November, 1990. The majority of the subsidence in this area is expected to occur during the following six months and should be generally settled by the time the nests would be utilized by the Cooper's Hawk(s) during the breeding and rearing season (assuming the nests are actively utilized). As you know, subsidence cannot be stopped once it is started, but in this case we believe it will be nearly complete and have no affect on the nests during the 1990, 1991 or future nesting seasons. Please do not hesitate to contact me should you have questions or require further information. As we plan to initiate mining of this area in the near future, we would appreciate your prompt attention to this matter. Sincerely, ~~~~f Kathleen G. Welt Environmental Engineer KW/rrw cc: R.D. Pick J.L. Coffey D. P. Conn Richard Holbrook, OSM Matthew Hayes, CMLRD