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March 27, 2012 <br />Barr Engineering Company <br />4700 West 77 Street • Minneapolis, MN 55435 -4803 <br />Phone: 952- 832 -2600 • Fax: 952 - 832 -2601 • www.barr.COM An EEO Employer <br />Minneapolis, MN • Hibbing, MN • Duluth, MN • Ann Arbor, MI • Jefferson City, MO • Bismarck, ND <br />Kathy Welt <br />Mountain Coal Company <br />West Elk Mine <br />P.O. Box 591 <br />Somerset, CO 81434 <br />Re: HR -1 Slide Summary <br />Refuse Pile Expansion East <br />Dear Ms. Welt: <br />This letter summarizes the design recommendations and construction observation performed by Barr <br />Engineering Company (Barr) as part of the remediation activities for the slide which occurred in <br />2011 along haul road HR -1. This area is part of the development of the Refuse Pile Expansion East <br />(RPEE) at West Elk Mine near Somerset, Colorado, as shown in Figure F -1. <br />Slide Development <br />A northward moving earth slide was observed during the spring of 2011 in a portion of haul road <br />HR -lthat was under construction. The location of the slide, hereafter referred to as the East Slide, <br />was approximately between HR -1 Stations 8 +00 and 12 +00, and extended up to a large sandstone <br />outcrop just below the upper haul road leg at Station 18 +50 as shown in Figure F -2. Also as shown in <br />Figure F -2, the width of the displaced mass (east -west) was about 400 feet and the length of the <br />rupture surface (north - south) measured about 300 feet with the vertical offset measuring about 5 feet <br />at the headscarp. The material that comprised the sliding mass was colluvium consisting of sandy <br />lean clay with gravel, though sandstone cobbles and boulders were also present in the material. <br />A second associated earth slide occurred on December 21, 2011, on the west end of the first slide <br />described above. The location of the slide, hereafter referred to as the West Slide, was approximately <br />between HR -1 Stations 6 +00 and 8 +00 as shown in Figure F -2. As shown in Figure F -2, the width of <br />the displaced mass (east -west) was about 200 feet and the length of the rupture surface (north- south) <br />measured about 200 feet with the vertical offset measuring about 4 feet at the headscarp which was <br />located within the haul road itself. The material that comprised the sliding mass appeared to be <br />identical to the material in the first slide. <br />The likely cause of the slides was very wet colluvial soils. It is believed that the native soils <br />overlying the bedrock in this area have created "dams" over bedrock seeps and caused pressure <br />buildup, which eventually resulted in saturated soils and failures as observed. <br />P:AMplsA06 CO \26 \06261003 Haul Road Slide RepairAWorkFiles\Report \MCC Slump Repair Letter 2012- 03- 27.docx <br />