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1.0 Introduction and Background <br />This report summarizes actions taken to stabilize a slide area along Haul Road HR -1, presents <br />information for the addition of slope stability monitoring devices (mirrors, inclinometers, and <br />piezometers) for the haul road area and for the Refuse Pile Expansion East (RPEE) buttress and <br />refuse pile, and presents revisions to the RPEE drainage plan and sediment ditch. This report has <br />been prepared to present information regarding these items and support a technical revision (TR- <br />129). <br />1.1 Background <br />Construction of a coal mine waste bank, known as the Refuse Pile Expansion East (RPEE) was <br />permitted in early 2010. Mountain Coal Company began construction of the RPEE in the summer of <br />2010 and was completed in early 2012. The RPEE construction included placement of a rock <br />buttress at the toe of the proposed waste bank, clearwater diversions, sediment ditches, and haul road <br />construction. <br />An area along the lower reach on Haul Road HR -1 from the Refuse Pile Expansion (RPE) to the <br />RPEE began to slump in spring 2011. The area was investigated and repaired during the 2011 <br />construction season. A secondary slump occurred in December 2011 and was repaired in early 2012. <br />The current approximate limits of the two slumps, combined, are shown on Figure 1. Additional <br />information covering the investigation, repair design, and construction of the slump repair is <br />provided in this report. <br />A monitoring plan, including mirrors, inclinometers, and piezometers, was proposed in the original <br />RPEE permit design approved in Technical Revision TR -120. Implementation of the first <br />components of the monitoring plan is proposed since the initial phase of buttress construction has <br />been completed and refuse placement has started as approved in Minor Revision MR -383. The haul <br />road slump area will also be monitored to confirm the effectiveness of the repairs. The specific <br />instruments and data to be collected are presented in this report. <br />Finally, detailed site conditions identified during construction at the RPEE and as a result of repairs <br />to the Haul Road HR -1 slump area require that modifications be made to the drainage plan and <br />sediment ditch design. Additional information concerning the conditions and the revised design is <br />included in this report. <br />P Mpls 06 CO 26 06261003 Haul Road Slide Repair WorkFiles Report MC(' Slump Repair- Instrumentation- DrainRev_2012 -05 -25 docx <br />1 <br />