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Jim Herron -2- February 10, 1982 The applicant's consultant, John F. Abel, Jr., observes, in Appendix W of the addendum to the Roadside and Cameo mine application, that damage may occur to the Ute Water District's facilities if pillar failure and accompanying ground subsidence occur. The consultant recommends that back- filling of workings within 100 feet of these facilities should be completed in order to prevent possible material damage. However, the applicant's mining plan does not include backfilling of these areas. In light of Dr. Abel's recommendation, the application should specifically address why this recommendation has not been accepted. Further, the applicant should describe how it proposes to prevent material damage to the potentially affected structures. Under the definitions of Rule 2.05.6(6)(e)(ii)(A), restoration of affected structures to their pre-subsidence condition constitutes an acceptable control plan to mitigate material damage. If the applicant intends to propose such a subsidence control plan to satisfy the requirements of Rule 2.05.6(6), the application must contain a detailed description of proposed mitigative techniques. The applicant proposes to prevent material damage to the raw water collection pipelines which exist above the proposed Cottonwood lease's underground mine workings through the retention of stable pillars within 100 feet of the pipe- lines, However, the majority of the Cottonwood lease area is proposed to be extracted through longwall mining techniques. The use of longwall mining equipment will not allow the retention of pillars as described in the sub- sidence control plan. The analysis of potential effects to the Ute Water District's facilities, contained within Appendix W of the original application, projects maximum strains resulting from possible pillar failure within the protected areas which would not exceed the normally allowable levels of strain for water pipelines. The applicant believes that this analysis sho:~ld also apply to the raw water collection pipelines which exist above the proposed Cottonwood lease underground mine workings. However, the strain predictions contained within Appendix W are projected assuming the use of room and pillar extraction techniques. Without the support rendered by the remnants of failed pillars, Iongwall trough subsidence magnitudes and the accompanying strain levels might result in damage to the pipelines within the Cottonwood lease area. The applicant should amend the application to resolve the apparent conflicts between the mine plan for the Cottonwood lease and the subsidence control plan proposed to protect the overlying pipelines. Further, the application should be amended to include an appropriate projection of maximum subsidence magni- tudes and strain levels to be encountered above Iongwall extracted panels within the Cottonwood lease. Finally, the application should present an appropriate subsidence control plan. As mentioned above, a detailed plan to affect restoration of the pipelines to their pre-subsidence condition would constitute an acceptable subsidence control plan. In the case of water supply facilities, prompt detection of any damage and prompt repair to avoid dis- ruption of service represents a significant component of an acceptable subsidence control plan.