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12.0 IMPACTS BENEATH THE MINED E COAL SEAM <br />Based on mapping and observations by Dunrud in the B Seam of the Somerset Mine, impacts to <br />the coal and rocks below the mined coal bed are expected to be limited to about one mining <br />thickness. There is no expected mining impact to the underlying D Seam because its top commonly <br />occurs at a mining thickness below the base of the E Seam. Furthermore, impacts to the floors of <br />the mine workings are expected to be limited to the chain pillars, because the floors of the longwall <br />panels will be loaded with caved roof rocks and overlying strata before deformation in the floor can <br />occur. <br />Floor heaving, pillar punching (the pillar punches into the floor and roof rocks), and squeezing (also <br />known as plastic flowage, see Dunrud 1976, p. 36) are the only expected deformations in the <br />immediate mine floor, which commonly consists of impure coal, shale, sandstone, and claystone. <br />Deformation in the floors of the chain pillars is expected to occur after the longwall panel is mined <br />and the pillars begin to yield. <br />• <br />• <br />Tetra Tech - 090717/P 30