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• is not allowed under special condition 2 of the approved <br />mining plan unless specifically authorized by BLM. Amore <br />specific condition is proposed for approval of this mining <br />plan modification to allow such subsidence only if approved <br />by BLM and only if WECC demonstrates that it would occur <br />when the nest is inactive or not being used during the <br />breeding and rearing season. <br />4. Cumulative impacts <br />The total coal mining activities (i.e., all mines) within <br />the North Fork of the Gunnison drainage basin will have a <br />very minor impact on the quantity of water available in the <br />basin. <br />At the Mt. Gunnison No. 1 mine, the cumulative impact of <br />mining both the F seam and the B seam under the proposed <br />mining plan modification would not substantively change from <br />the impacts associated with mining only the F seam. A total <br />of about 2,700 acres is expected to subside due to all <br />mining operations in the permit area. <br />In about 500 of these acres, both the F seam and the B seam <br />would be mined. Subsidence in this area of double seam <br />mining, almost all of which is within Section 20, is <br />expected to be up to 10 feet if longwall mining is used in <br />...•- the B seam. If room-and-pillar mining is used in the B- <br />seam, total subsidence is expected to be up to 4 feet. <br />Only the B-seam would be mined in about 300 acres of the <br />area (i.e., E1/2 of Section 19 and the W1/2W1/2 of Section <br />20), and subsidence would be either less than 2 feet or up <br />to 8 feet depending on whether longwall or room-and-pillar <br />methods are used. <br />In the remaining 1900 acres (approximate) only the F seam <br />would be mined, and less than 2 feet of subsidence is <br />expected. <br />Cumulative impacts associated with the anticipated mining <br />over the life of the mine are addressed in BLM's 1979 West <br />Central Colorado Coal Environmental Impact Statement. The <br />proposed mining plan modification for which this <br />environmental assessment was prepared is a subset of the <br />proposed life-of-mine plan evaluated in the BLM <br />Environmental Impact Statement. <br />u <br />13 <br />