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-57- <br />CWI, in response to Division adequacy comments, has completed strain <br />projections for the structures inventoried on Map 9-7. Strain projections <br />have also been completed for the two water pipelines which cross the <br />life-of-mine potential subsidence area. These two pipelines are the Pitkin <br />Mesa pipeline, which supplies potable water to roughly 160 domestic taps, and <br />the Industrial Water Supply pipeline for the Orchard Valley Mine. <br />Subsidence Control Plan <br />CWI has proposed a subsidence control plan to prevent material damage from <br />occurring to the renewable resource lands within Steven's Gulch and East <br />Roatcap Creek. The U. S. Bureau of Land Management lease C-37210 also bears <br />stipulations addressing these same areas. <br />CWI proposes to control subsidence within these renewable resource lands by <br />limiting the extraction of coal beneath these potentially impacted surficial <br />aquifers. In areas of the renewable resource lands separated from the "D" <br />seam by less than 600 feet, extraction will be limited to seven 20-foot wide <br />mains developed on 120' by 80' centers, resulting in permanently retained 100' <br />by 60' pillars. Pillar stability calculations project Ashwin/Wilson safety <br />factoring in excess of 2.0 for pillars of that size at 600' of overburden <br />depth. Further, in areas of the renewable resource lands separated from the <br />"D" seam by between 600' and 800' of overburden, permanent 60' x 60' pillars, <br />with Ashwin/Wilson safety factoring in excess of 1.5, will be retained. In <br />both of these areas, mining will be limited to development without retreat <br />extraction. <br />With the exception of the ruins depicted as Structure No. 27, the inventoried <br />buildings will be protected by the retention of solid coal pillars of 300' <br />radius beneath each of the potentially affected buildings. <br />CWI's strain projections anticipate potential, repairable damage (non-material <br />damage) to the two existing water pipelines, the Steven's Gulch Road, assorted <br />trails, ponds, and springs within the permit area. In each case, a preferred <br />repair methodology has been presented within the Subsidence Repair Handbook <br />portion of the amended permit application. <br />Calculations have been included to demonstrate that adequate water storage <br />exists in the Pitkin Mesa Pipeline water distribution system to assure reduced <br />service and safe fire coverage in the event of a subsidence disruption of the <br />pipeline. The company does not propose to mine beneath the Pitkin Mesa <br />Pipeline during the 5-year permit term. The company will be required to <br />elaborate upon plans to detect, locate, and repair pipeline ruptures, prior to <br />receiving approval for any extraction beneath the pipeline. <br />Subsidence Monitoring Program <br />CWI proposes a subsidence monitoring program with three components; visual <br />inspection, wide-spaced grid subsidence monumentation, and close-spaced <br />high-resolution subsidence monuments. The visual inspection phase consists of <br />a walk-over of the ground surface above mined areas with semi-annual <br />