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The 1630 permit revision application, approved last fall, provided a valid determination of an analogous buffer zone width adjoining the divide, in order to assure prevention of impacts south of that divide. This same rationale could be applied to the streams, resulting in buffer zone widths of 560 feet on each side of the alluvial deposits containing the channels. However, this will result in the delineation of tw•o substantial buffer zones.. Correspondence between CVII12D and wECL regarding problans correlating the aerial survey and proposed and approved changes are attached. 1CECC did not receive a copy of Jim Pendleton's internal maro to Susan :~bwry regarding this matter. This correspondence will be added as an addendtm to Exhibit 3.4.3.,E when the adequacy response information is incorporated into the permit docurent. West Elk Coal Carr2any ~.as re-e•+aluated the life of "F" seam mine plan and based on coal heights, quality, and other mineability criteria revised the mine plan accordingly. The result of these changes is a substantial reduction in the areal extent and overall reserve in the "F" seam. This revised plan should better reflect anticipated mining in the "F" seam. ttE~ has revised Exhibit 3.4.4.B.1 to show the subsidence protection method to be used under the Dry Fork of Minnesota Creek and Lick Creek (although it is not thought at this titre that mining will reach the Lick Creek drainage due to mineability criteria, it is included to present a conser•+ative analysis). The subsidence protection plan which is basically a "no extraction" plan , except for a narrow corridor where development only matt entries will cross under the creeks. This plan will be used until subsidence and hydrologic data fran the nnnitoring of panel I5-1W can be utilized to verify a limited extraction plan for the creek zones. The subsidence protection zones are shown on Exhibit 3.4.4.6.1 which is included in an earlier portion of this adequacy response. The subsidence protection zones were derived by finding the slope break line of the valley bottan containing the creek (this would take into account any possible alfu•+ial areas), adding 100 feet to this on both sides of the creek, and then projecting a 20.5 degree angle of draw downward. Tlie area within these boundaries will be areas of zero extraction with the excep*.ion of the development main entries crossing the protection zone. The attached schanatic shows graphically the methodology used to determine the subsidence protection zone. The width of the protection zone varies with depth of overburden. No subsidence will occur within the valley bottan plus l00 feet on either side (the l00 feet is a buffer zone to account for variations in the projected 20.5 degree angle of draw). Secondary or retreat mining will take place up to the boundary of the protection zone shown on Exhibit 3.4.4.D.1. IX-2