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• 30 November 2005 <br />Memo to: Collin Stewart, Greg Hunt <br />From: Brad Lindsay <br />12E: 2005 Subsidence Crack Mapping Update <br />Field Work <br />Field surveys were conducted above the current and recent mining areas on the 26`h of April, the <br />30th of August, and the 15`" of November 2005. Each new crack was photographed and the <br />orientation, length, width, and vertical displacement were measured. <br />No new cracks were found during the April survey. Observations were noted of the healing of <br />cracks which were identified in 2004. Seven new cracks were observed and measured during the <br />August survey. Seven more new cracks were observed and measured during the November <br />survey. Due to snow on the ground in November, cracks that extend into vegetated areas were <br />difficult to observe and measure. <br />Observations <br />• New cracks were observed above the B I panel. The majority of cracks are found along ridges <br />and areas of topographic high. Few cracks are observed along the valley bottoms. The same <br />pattern was observed in the 2004 surveys. Cracks observed in 2005 range from less than Y~ inch <br />to approximately 15 feet wide. The majority of the cracks are less than 5 inches wide. Toward <br />the NW end of the B 1 pane], most of the cracks are perpendicular to the panel. Many cracks <br />were also observed at the southeast end of the B 1 panel. Most of these run fairly parallel with <br />the panel. <br />Files <br />Information collected is contained in an Excel file (SUBSIDENCE CRACK MAPPING.xIs). <br />The AutoCAD map (Subsidence-Crack-Nov05-source.dwg) was updated with the actual lengths <br />and orientations of the cracks. Digital photos of most of the cracks were taken and placed in <br />Subsidence Photos folder. All these files can be found on the server under Autocad/Subsidence. <br />A paper copy of each file is attached. <br /> <br />M -1 <br />