Laserfiche WebLink
Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• hcdrock has hM1 rut through, or where hrush and tree have heen Pulled out of soil and/or <br />L-0IluVi11111. <br />• <br />• <br />For diagnostic Purposes. the largest difference hetween Subsidence cracks and construction <br />cracks is that the construction Cracks: 1 ) have a less regular pattern, 2) are related to the material <br />thCV 000U1- in, and 3) lack any spatial relationship to the lom_pwall mining geometry. <br /> <br />r-A <br /> <br />Vii • ,?• _ ' y ? -`v,• ,`?. <br />- ,, !! <br />P <br />Figure 2. This cut bank in bedrock is located above mined Longwall Panel <br />17 in an excavation area at well site MDW 17-02. Cracks on either side of <br />the dominant, irregular crack (right middle) are natural or the result of <br />construction. The most prominent irregular crack has an estimated 75 <br />percent likelihood of being mine related. <br />2.3 Desiccation Cracks <br />Desiccation cracks tend to occur in claystones and siltstones of the Meaverde and Wasatch <br />Fortnatons ill the 'Vest Elk dine area where the rocks are weathered to clays and 'alts (Figure 3). <br />The. Process of desiccation 111VOlves the shrinking of previously welted Clavs and silt: during tile. <br />drying Process. <br />631-032.790 <br />August 2008 <br />Wright Water Engineers, Inc. <br />Page 6