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<br />' -4- <br />The application includes a thorough technical projection of anticipated <br />subsidence phenomena and areas of potential impact, contained within <br />Appendix XXVII. This analysis, assuming a conservative angle of draw of <br />60° from horizontal and the subsidence relations developed by Dunrud (U. S. <br />Geological Survey Professional Paper No. 969) at the nearby Somerset mine, <br />conforms with the prudent state-of-the-art. One clerical oversight exists <br />within the documents, which can be rectified with the imposition of the <br />following stipulation. <br />Stipulation No. <br />THE DIVISION DIRECTS WESTERN SLOPE CARBON TO AMEND EXHIBIT 2.05.6-C <br />TO INDICATE THE ANTICIPATED LIMITS OF PROJECTED SUBSIDENCE DUE <br />TO MINING WITHIN THE E-SEAA1. THIS LIMIT LINE IS DISCUSSED ON <br />PAGE 2.05-66 OF THE APPLICATION, BUT WAS INADVERTENTLY LEFT OFF <br />THE FINAL DRAFT OF THE EXHIBIT. <br />The applicant proposes to control subsidence effects to Colorado Highway 133 <br />through the retention of appropriate barrier pillars adjoining the highway. <br />This subsidence control plan assumes a conservative angle of draw of <br />60° from horizontal. <br />In order to verify the site-specific angle of draw and to discern whether <br />any unanticipated subsidence effects might manifest themselves adjoining <br />Highway 133, Western Slope Carbon has proposed the installation of an <br />extensive subsidence monitoring network, depicted on Exhibit 2.05.6-C. <br />This network includes subsidence monuments above the west mine longwall <br />extraction area, the east mine room and pillar extraction areas, and <br />adjoining the potentially affected portion of Colorado Highway 133. The <br />operator commits to performing surveying of the subsidence monuments on a <br />quarterly basis and to submitting the monitoring data results semi-annually. <br />The monitoring program is deficient in only one aspect, in that the company <br />states; "...that cessation of subsidence monitoring would occur after we <br />have demonstrated a reasonable period of time (I to 2 years) without <br />significant subsidence movement." The applicant then goes on to indicate <br />on page 2 of Appendix XXVII-2 that they consider "significant subsidence" to <br />be of the order of I-half foot per quarter". Similarly, on page 4.20-7 of <br />the application, the applicant observes that they intend to cease monitoring <br />potential subsidence in the area of an intermittent stream channel 12 <br />months after undermining of that channel is complete. The Division, because <br />it does not recognize such arbitrary definitions or limitations to subsidence <br />monitoring responsibility, imposes the following stipulation upon permit <br />approval. <br />Stipulation No. ~ <br />THE DIVISION DIRECTS WESTERN SLOPE CARBON TO CONTINUE MONITORING <br />THE SUBSIDENCE MONITORING NETWORK MONUMENTS, DEPICTED ON EXHIBIT <br />2.05.6-C, UNTIL CESSATION OF MONITORING IS APPROVED, IN WRITING, <br />BY THE DIVISION. <br />With the imposition of these two stipulations, the Division finds the <br />application to be in conformance with the subsidence regulation requirements <br />of Rules 2.05,6(6) and 4.20, <br />