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Page 2 of 3 <br />Slide ST -02 Area — Ground Engineering Consultants, Inc. Report <br />1. The ST -02 slide area appeared to be stable during all of the site inspections to date. The <br />slopes do, however, appear to be slightly steeper than the designed slopes of 2:1. There is <br />no final slope steepness for the regraded ST -02 slide area shown on the drawings in the <br />Ground report. Please update the Ground report drawings to show the final slope <br />configuration and steepness. Please ensure that the final regraded slope configuration <br />drawing is clearly labeled as such. <br />2. The Ground report has two drawings titled "Anticipated Final Geometry ", in which the <br />factor of safety is shown as slightly more than 1.3, which is acceptable. There is not, <br />however, a drawing that shows the actual final slope geometry with its corresponding <br />factor of safety. Please provide a drawing that shows the actual final slope geometry with <br />its corresponding slope steepness and factor of safety. <br />HR -1 Slide Area — Barr Engineering Co. Report <br />3. During the 10 April 2012 site inspection (and later inspections) it appeared as though the <br />reconstructed HR -1 fill slopes appeared to be steeper than 2:1. There are no labels on the <br />as -built drawings showing what the reconstructed slopes are. Measuring the reconstructed <br />slopes on the Figure 5 details and the stability analyses geometry in the Barr report with a <br />protractor, the reconstructed slopes appeared to vary from 2:1 to 1' /z: 1. Please provide a <br />discussion of the reconstructed slopes at the HR -1 slide area and correct and resubmit the <br />as -built drawings with these slopes labeled and stated for the Division's review. <br />4. As noted in several of the Division's inspection reports, there appeared to be large tension <br />cracks in the backfill. Representatives of Mountain Coal believed that the cracking was <br />related to frost that was thawing (much of the work was done in the winter months). <br />Mountain Coal will need to ensure the long -term stability of the HR 1 slide area. Please <br />provide the Division with a short discussion on how Mountain Coal will monitor these <br />cracks to ensure that they were, in fact, surface cracks and not larger tension cracks. <br />5. In page 1 of Section 1.1 (Background) of the Barr report there is a statement that <br />construction of the RPEE began in the summer of 2010 and was completed in early 2012. <br />While this statement is true for the phase I buttress and colluvial fill, it is not true for the <br />entire RPEE. Please clarify and correct the construction dates contained in this portion of <br />the Barr report. <br />6. It appears that there are two stability analyses in the Barr report. The first for the <br />modeled designed slope, and the second for the as -built slope. The analyses shows that <br />there was a decrease in safety factors from the modeled design, shown in Table 3 on page <br />7, compared to the as -built design shown in Table 5 on Page 10. That as -built analysis <br />shows that a saturated reconstructed slope under seismic conditions could fail (i.e., below <br />unity, or a safety factor below 1). A safety factor of at least 1.3 is required for all <br />reconstructed slopes. Please provide the Division with a detailed discussion of the as- <br />