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Rock Logic Consulting <br />RLCR'Ionsulting ck Logic PO Box 544 • Cedaredge, CO 81413 <br />LLC Phone: (435) 851-9044 • rocklogicconsulting@gmail.com <br />Brad Lindsay • Consulting Geologist <br />Memorandum <br />Date: 12 August 2010 <br />To: Jim Abshire <br /> Joe Brinton <br /> Bill Bear <br />From: Brad Lindsay <br />Subject: Spring 2010 Subsidence Crack Mapping <br />Field Survey <br />A thorough field survey above the B9 longwall area was conducted in July 2010. The mined B9 <br />panel underlies a high east-west trending ridgeline between Dove Gulch and Sheep Corral Gulch. It <br />also underlies Sheep Corral Gulch itself. Slopes and the top of the ridge and the gulch were hiked to <br />observe visual evidence of subsidence. Thick brush on the north side of the ridgeline prevented <br />extensive hiking past the north end of the B9 panel. A GPS unit was utilized in track mode to record <br />the path of all traverses and locations of cracks observed. Each new crack was photographed and <br />the orientation, length, width, and vertical displacement were measured. <br />Observations <br />Cracks were observed on and near the top of the ridge. Many cracks were discovered on the south <br />facing edge of the ridge going down into Sheep Corral Gulch. One crack (02-10) is large and cuts <br />deep into colluvial material as well as sandstone outcroppings. No cracks were observed on the north <br />facing slope of Sheep Corral Gulch. The attached map shows the path that was hiked and location <br />and approximate size of cracks encountered. <br />Files <br />Crack measurements and field notes are recorded in an Excel file (Subsidence Crack Mapping Spring <br />10.xls). The AutoCAD map (Subsidence-Crack-JulylO-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.