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R Rock Logic <br />Consulting LLC <br />Memorandum <br />Date: 15 July 2013 <br />To: Jim Abshire <br />Bill Bear <br />Art Etter <br />Rock Logic Consulting <br />PO Box 544 • Cedaredge, CO 81413 <br />Phone: (435) 851 -9044 • rocklogicconsulting @gmail.com <br />Brad Lindsay • Consulting Geologist <br />From: Brad Lindsay <br />Subject: Spring 2013 Subsidence Crack Mapping <br />Field Survey <br />A thorough field survey above the B -13 longwall area was conducted on May 10`h and June 13`h 2013. <br />The mined B -13 panel runs north -south west of terror creek. Areas of both mildly sloping terrain and <br />steep topography overlie the panel. Traverses over the panel were hiked to observe visual evidence of <br />subsidence. Thick brush, cliffs, and steep slopes exist in the area. A GPS unit was utilized in track <br />mode to record the path of all traverses and locations of cracks observed. Each new crack was <br />photographed and the orientation, length, width, and vertical displacement were measured. <br />(lhcPrvntinnc <br />Twelve separate cracks were observed overlaying the B -13 panel. Most cracks were found on steep <br />surfaces and along ridge lines. A few were found in flatter topography. They range from less than an <br />inch to 24 inches wide and over 200 feet long. Despite the thorough search, fewer cracks were <br />observed over the B -13 panel compared with the B -12, B -11, and B -10 panels. Thicker vegetation <br />yielding more leaves on the forest floor may partially contribute to this fact. The topography may <br />also be a factor. Cracks over the B -10, B -11, and B -12 panels continue to heal. <br />Files <br />Crack measurements and field notes are recorded in an Excel file (Subsidence Crack Mapping Spring <br />13.xls). The AutoCAD map ( Subsidence - Crack- Junel3- source.dwg) was updated with the track <br />surveyed and lengths, orientations, and locations of new cracks observed. Digital photos of <br />the cracks are attached. <br />