2014-12-15_INSPECTION - C1981019

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December 10, 2014C-1981-019/Colowyo Coal MineRDZ Four sumps along the road to the Taylor ponds were inspected. Sump #2 contained a lot of water; the berm beside it requires maintenance. Sump #3 was clear of water and sediment. Sumps 4 and 5 were holding water; no problems were identified. Ditchouts from the road up the valley from the sumps were also inspected; these do not receive runoff from the haul road (which is above the Taylor Creek Road) as the sumps do. There were no signs of sediment loading from the road or sumps onto undisturbed areas near the Taylor Creek Buffer Zone. The following ditches were inspected: East Taylor, Taylor Tributary, Final East Pit, Streeter Gulch, West Pit Coal Road, West Pit Fill and East Taylor Pond. There is continual erosion in East Taylor Ditch, but it appears to be no worse than past months (this problem and solution are the subject of TR-104). No other erosion or other problems that need to be addressed by Colowyo were seen. Rob Zuber inspected the portion of Streeter Gulch Ditch where possible issues with the channel were identified by the Division in the Spring of 2014. In particular, Area 1 (shown in July 2014 letter from Tri-State on this ditch) was walked. It appears that sediment may have been transported onto undisturbed land for 50 to 70 feet (this land is owned by Colowyo). This reach of the ditch is very flat, however, and it would not be feasible to address this issue without creating a good deal of disturbance of reclaimed land. The reach below Area 1 is a well defined channel with no problems. The 2014 construction of the upper reach of the Final East Pit Ditch was inspected for compliance with design specifications for cross-sectional area, slope, and riprap size. Using a measuring stick, the bottom width and depth was measured at three locations along this reach of the channel. The bottom depth was measured to be 12 to 15 feet, which is in line with the design of 12 feet. The depth was measured to be greater than two feet, which is in line with the design of 1.1 feet (including freeboard). Side slopes were all approximately 2:1. In some cases the side slopes appear to be flatter than this (3:1), which is acceptable. The longitudinal slope was measured with a clinometer (Sokkia) at 6% –8%, which is in line with the design (4% –16.8%). Riprap was generally larger than the D50 design of 6 inches, which is acceptable. The riprap appeared to be well sorted and stable. The November 2014 construction of the lower reach of the West Pit Coal Road Ditch was inspected for compliance with design specifications. The depth (measured to be 2 to 3 feet), side slopes (2:1), and material (vegetation with erosion mat) are in compliance. The erosion mat should be monitored for erosion, especially at the upper end, although this mat is not required for compliance. Keeping this mat in place will be good practice to help establish vegetation growth. The previously constructed reach of the West Pit Coal Road Ditch (above the newly constructed reach) was also inspected, and no problems were found. No problems were found with the West Pit Fill Ditch, although the recently broken riprap should be monitored and, if deemed necessary, spread to the sides to better form a trapezoidal channel. Number of PartialInspection this Fiscal Year: 4 Number of CompleteInspections this Fiscal Year: 2 413 Page of