2018-01-23_GENERAL DOCUMENTS - C1981041

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27 C1981-041 RN7 findings C. Stream Channel Diversions Construction of the Cameo Refuse Disposal Areas involved the installation of a permanent ephemeral stream channel diversion along a segment of Coal Canyon in the vicinity of the refuse areas. A total of approximately 600 feet of the Coal Canyon drainage was diverted. As part of the design for CRDA-2, the Coal Canyon drainage channel was realigned to provide a more uniform, controlled flow between CRDA 1 and 2. The four rock check dams constructed in the channel have caused significant deposition and necessitated frequent maintenance. In order to assure the channel is in equilibrium with the flow regime, the rock check dams were removed and the excess sediment was harvested and used as refuse cover soil during the 2002 reclamation project. The drainage channel was graded to an approximate uniform grade to the cross sections presented on Exhibits 53 and 55 of the permit document. Berms located along the middle and lower sections were leveled so the channel blends naturally into the adjacent terrain. Berms are not utilized to provide the necessary flow capacity along the segment between the dip section concrete structure at the upper end and the two 81" by 59" culverts at the lower. Additionally, the Pond 6 embankment was built up and fortified with riprap. The rock from the check dams was used for the construction of rock groups placed on the reclaimed surface of CRDA-1 & 2 and other reclamation uses. Since material generated from the Coal Canyon Realignment was utilized for the reclamation of CRDA-2, the realignment was performed concurrently with the 2002 refuse pile reclamation project. During 2003, work was performed in Coal Canyon below the outlets of the large double culverts. Scour protection was provided at the outlet of the culverts. Pursuant to TR-42 approved in 2003, the Division approved the installation of a riprap transition zone at a “nick-point” in a lower segment of the Coal Creek channel, in the vicinity of the former Haul Road 2 channel crossing. Approximately 700-feet downstream of the double culverts, a transition zone was installed. See Exhibit 8B and Appendix 13-2, pages Misc-13 through Misc-22 of the permit document for details of the scour protection and transition zone. Scour protection was installed at the outlet of the upper dip section during 2002. Sections of the Coal Canyon permanent channel diversion near Ponds 6 and 10, and the Coal Gulch drainage in the vicinity of Pond 11 were originally planned and approved by the Division to be re-aligned and modified in conjunction with removal of the ponds. The Coal Gulch and sections of Coal Canyon drainage were going to be diverted back through the pond locations which would approximate these drainages original configuration. However, during a meeting between SCC and the U S Corp of Engineers it was recommended that Coal Canyon drainage, which was previously approved for realignment during the reclamation of Ponds 6 and 10, remain in its current configuration. The re- routing of the Coal Canyon and Coal Gulch drainages would require a permit from the U S Corp of Engineers. Carrie Sheate of the US Corp of Engineers proposed that realignment of Coal Canyon for the sake of routing the drainage back to its original contours would not be a justifiable reason for issuing a Corp Permit. The Division concurred with not re- disturbing the current alignment of Coal Canyon and Coal Gulch and approved PR-5 leaving these drainages in their present alignment and configuration. Coal Canyon drainage and Coal Gulch are stable in their current position.