2017-05-08_REPORT - C1982056 (3)

Home Browse Search

between adjacent Stations. Final differential gradients are predicted to be at or below 0.3% following subsidence from each of the planned longwall panels. 3. Both of the two remedial methods outlined in this report have been successfully implemented during undennining ofjthe Energy Spur. There is every reason to conclude that they will,l continue to be successfully applied to remediating subsidence associated with extraction of the panels in the Wolf Creek Seam. 8.2. County Road 33 Section 4 predicts that County Road 33 will be subject to just under 80 -inches of subsidence as it crosses over the shallower panels in the Wolf Creek seam. Gradient changes of just under I% and surface strains of 0.005 are expected to result in surface cracking of the chip sealed surface. Prior mitigation of similar impacts to County Road 33 has involved sealing of these surface cracks. 8.3. Fish Creek, Foidel Creek, and Middle Creek. The evaluation presented in Section 5 predicts that Fish Creek will overflow its high bank(s) with the following impacts to Fish Creek and its floodplain: 1. A maximum increase in Fish Creek bottom gradient of 0.024 (2.4%). 2. An increase in the surface area of Fish Creek following coal extraction in Panels 9 -East, 8 - East, 7 -East, and 6 -East of under 50 acres. Impacts to Foidel Creek are expected to be minimal with a predicted increase in the surface area of Foidel Creek following coal extraction in Panels 1 -East through 4 -East of under 5 acres. It is our understanding that the magnitude of predicted surface water area changes in the Northern Mining District contained in our 1999 and 2002 reports and over the Western Mining district in 2009 were never realized illustrating the conservative nature of these predictions. This is likely due to the dynamic process where differential subsidence displacements are readily accommodated by the natural processes of erosion and deposition that occurs rapidly under the high flow conditions experienced during spring months. 8.4. Power Transmission Lines. Several conclusions can be drawn from the preliminary work, described in Section 6, including: 1. Structures on the Foidel Creek -Steamboat line are predicted to subside by up to 6 -feet 2. Structures on the Archer -Hayden line are predicted to subside by just over 4.5 -feet. 3. Structures on the Craig -Hayden -Steamboat line are predicted to subside by just over 4 -feet 4. Maximum daily subsidence is predicted to be less than 6 -inches per day. 5. The duration of subsidence effects a each structure is exp cted to be between 25 and 35 - days. 6. In the case of the Archer -Hayden an I Craig -Hayden -Steamboat lines, the length of the traveling subsidence profile means that each structure will react independently which should for the most part eliminate the potential for complex interactions. 7. Subsidence, tilt and strain magnitude at each Archer -Hayden and Craig -Hayden -Steamboat structure are predicted to be lower than previously experienced by WAPA's line that crossed the Eastern Mining District and by these two iilines when they were previously undennined by 19 -Right in the Northern Mining District. 8.5. Water Wells The evaluation resent d in Section 7 rediJs impacts to wells completed in the Wolf Ci)eek Seam p �j p p P J and its immediate overburden. Minor impacts may also occur in shallow overburden weds but are likely to be minor with recovery within one year after undennining. 8.6. Monitoring Requirements