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2.05.6(6) <br />Also when, during development of the panels near the outcrop, low quality <br />coal is encountered, one row of development pillars will be left in place to <br />prevent the potential crushing, sliding, or other failure near the outcrop. See <br />Exhibit 15, Section 1.7. Zones Along Outcrop Barrier Pillar. <br />The applicant plans to mitigate the risk of damage to the Pitkin Mesa pipeline <br />by installing a schedule 80 6 -inch diameter heat fusible high density <br />polyethylene pipe (HDPE) adjacent to the existing Pitkin Mesa pipeline. The <br />new pipe will be placed in a trench excavated next to the existing pipeline. <br />The new pipe will replace the existing pipeline. The existing pipeline will be <br />capped and remain in place. <br />The new pipeline will be joined with the existing pipeline on each end of the <br />pipe replacement project. The tie in will take about one day. The Pitkin <br />Mesa Water Pipeline flows into a 500,000 tank. The water users obtain their <br />water from the tank. The water users consume about 40 gpm during the <br />winter. The 500,000 gallon tank has about an eight day supply. Therefore <br />the water supply to the Pitkin Mesa water users will not be interrupted. <br />The fundamental of heat fusion welding is to heat two HDPE pipe surfaces to <br />an appropriate temperature and then fuse them together by application of <br />prescribed force until cooling occurs, returning the material to its original <br />state and creating one homogeneous pipe. <br />As explained in Exhibit 15, Section 1.6, data from the Bowie No. 1 Mine and <br />field measurements of subsidence cracks in the Mesaverde Formation by <br />Dunrud (1976), indicate subsidence cracks may develop through overburden <br />thicknesses of up to 800 feet under unfavorable conditions. While <br />unfavorable conditions can not be defined exactly, they may include zones of <br />weathered coal and overburden. Under normal conditions, subsidence <br />cracks do not appear likely to propagate through more than 500 feet of <br />overburden. <br />MR -146 2.05-146- 01/27/14 <br />