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e <br />ESPEY, HUSTON & ASSOCIATES, INC. <br />• <br />5.0 VALUATION OF STRUCTURES AND FEATURES IN RELATION TO <br />SUBSIDENCE EFFECTS <br />5.1 STATE HIGHWAY 13/789 <br />It has been determined that secondary mining beneath State Highway <br />13/789 would cause considerable material damage to the structure. Therefore, <br />measures will be taken to protect it. A zone in each coal seam will have advance <br />mining only, with lazge enough pillazs left in place to adequately support the <br />highway and prevent subsidence. The specific angle of draw for the azea is unknown <br />but is expected to be in a range from 12° to 16°. To calculate the protective zones <br />shown on Exhibits S-2, S-3 and S-4, the Pennsylvania Subsidence-Control Guideline <br />was followed which states: <br />Where a structure is located on terrain that is level or slopes less <br />• than 5%, the lateral distance LD of the support azea from each side of <br />the structure is equal to the tangent of 15 degrees (0.27), multiplied by <br />the depth of cover (D), plus a safety factor of 4.6 m or: <br /> <br />To find the total length or width of the support azea, double the result <br />found for LD and add the length or width of the structure. <br />This guideline has been implemented in Pennsylvania, where angles of <br />draw vary from 25° to 30°, and has been very successful in protecting against <br />subsidence. Due to the success of the law and the lack of site-specific information <br />available, NCC has decided to follow the guideline to protect azeas that cannot be <br />subsided. The pazameters will be subject to change pending the implementation of a <br />subsidence control plan in Colorado or results from site-specific investigations. <br />The highways will be monitored to ensure that subsidence is not <br />occurring. Since mining operations will be within 100 feet of the right-of-way line <br />n <br />~J <br />5-16 <br />