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• CHAPTER IV ENVIRONMENTAL CONSEQUENCES OF THE ALTERNATIVES A. Alternative 1: Approval of the Proposed Mining Plan Modification with Special Federal Conditions. 1. General Except for the proposed new mining area in the ls, 2S, and 35 panels in Section 16, the proposed modifications to the sequence and layout of the room-and-pillar mining in the F seam should not create any new impacts nor change the effects on the environment that were discussed in OSM's November 1987 Environmental Assessment for the mining plan modification approved November 21, 1987. Except for mining-induced subsidence, other elements of the proposed mining plan modification (i.e., B-seam mining) should cause no new disturbance beyond that predicted by the current mining activities. 2. Subsidence The mining of the F seam in the ls, 2S, and 3S panels in Section 16 is expected to result in about 2 feet of • subsidence. The mining of the B seam is expected to result in less than 2 feet or up to 8 feet of subsidence, depending on whether room and pillar or longwall mining methods are used. As overburden thickness increases, the magnitude of subsidence is expected to decrease. The B seam will be mined in about 800 acres (i.e., E1/2 of Section 19 and most of Section 20) with overburden thickness ranging from 400 feet to 1000 feet. No subsidence or surface disturbance is expected in the 35.5-acre area in the Minnesota Creek drainage basin associated with the B-seam main entries. 3. Critical Elements a. Cultural, paleontological, or historic resource values The proposed mining plan modification should not result in damage to any important cultural, paleontological, or historic resources in the permit area. Few, if any, of these resources are expected to occur in the 800 acres above the B-seam mining area. As noted in BLM's 1979 Environmental Impact Statement, cracks and breaks in the • surface that could adversely affect cultural resources are 10