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<br />Exhibit 5a, utilizing the predictive methods developed by the British National <br />Coal Board, includes a prediction of maximum subsidence above the proposed <br />Foidel underground mine workings. This worst case prediction projects 5.0 <br />feet of surface subsidence. The applicant also includes a description of <br />overburden response to subsidence, which is in keeping with the prudent <br />state-of-the-art of subsidence prediction. The applicant predicts no effects <br />to the identified renewable resource lands. Foidel Creek and its associated <br />alluvial aquifer will be protected through limited extraction of the portal <br />entryway mains, as described and analyzed in Exhibit 5a. The applicant <br />projects a plausible scenario of overburden response, which includes a worst <br />case caving of the roof to 110 feet above the seam, and the occurrence of bed <br />separation and associated fracturing to 330 feet (30 extracted seam <br />thicknesses) above the roof of the mined seam. Above the zone of bed <br />separation, the overburden response is anticipated to be limited to gentle <br />deflection of existing beds. As a result, the Twentymile Sandstone, which <br />lies approximately 600 feet stratigraphically above the mined seam, is not <br />predicted to suffer any impacts from subsidence. <br />The applicant proposes a monitoring program to verify the projections of <br />structural and hydrological effects included within the permit application. <br />The applicant proposes to install subsidence monuments, depicted in Figure No. <br />7, to verify those mechanical projections included within Exhibit 5a. As <br />indicated on Map 4a, a high-resolution grid of subsidence monuments will be <br />installed above one of the southeasternmost panels within the Foidel Creek <br />mine workings. This panel is scheduled for extraction in 1985/1986. <br />Observations above this panel should serve to verify the angle of draw, as <br />effected by cross slopes, and the observed magnitude of vertical subsidence. <br />Monuments are also proposed for installation above the portal entryway mains <br />beneath Foidel Creek, in order to verify the stability of the limited <br />extraction method proposed for use beneath the creek and its adjoining <br />alluvial aquifer. All monuments will be surveyed quarterly, weather <br />permitting. Subsidence monitoring reports, prepared in accordance with the <br />format contained in Exhibit 11, will be submitted to the Division once every <br />six months. <br />The unoccupied structure located in the SE 1/4 of the SW 1/4 of Section 29, <br />outside but closely adjoining the projected area of potential subsidence, will <br />also be monitored quarterly. County Road No. 27 and the Denver and Rio Grande <br />Western Railroad spur will be visually inspected on a weekly basis. <br />Colorado Yampa Coal Company proposes to verify the projections of probable <br />hydrologic consequence due to subsidence through a program of ground water and <br />surface water quality and quantity monitoring. Proposed alluvial and bedrock <br />monitoring wells and surface gauging installations are depicted on Map 9a of <br />the permit application. The timetable for monitoring is presented on Table 8 <br />within Exhibit 10a, entitled "Hydrologic Monitoring Plan". <br />It is the finding of the Division that Colorado Yampa Coal Company's <br />subsidence evaluation, subsidence prediction and subsidence monitoring program <br />satisfies the requirements of Rules 2.05.6(6) and 4.20. <br />