Alleghany Road at Oregon Creek Bridge Rehabilitation (Lake or Streambed Alteration Agreement No. 1600-2015-0198-R2)

Alleghany Road at Oregon Creek Bridge Rehabilitation (Lake or Streambed Alteration Agreement No. 1600-2015-0198-R2)

The project is limited to structural rehabilitation of the historic bridge over Oregon Creek, improvement of the road approach, and stabilization of the creek bank. The rehabilitation of the bridge will include the replacement of the bottom truss chords, all siding, the floor system, including steel floor beams, longitudinal stringers, transverse deck planks, deck runners and wheel guards, abutment timber sill plates supporting the trusses; repair of the "sheds" at each end of the bridge and the roadway erosion; and stabilization of the abutments. Bridge rehabilitation will require that the bridge will be completely disassembled. As part of the rehabilitation, the entire deck system will be replaced with in-kind materials, including the steel floor beams and timber stringers, deck planks, runners, and wheel guards. A support system will be constructed behind the existing abutment walls to stabilize the existing abutments. All staging of equipment and materials will take place in paved areas of the Oregon Creek Day Use Area at the project site. All rehabilitation work and road approach improvements will be conducted above the ordinary high water mark (OHWM) of Oregon Creek, and no dewatering will be required for the project site. All rehabilitation work and road approach improvements will be conducted above the ordinary high water mark (OHWM) of Oregon Creek, and no dewatering will be required for the project. The embankments adjacent to the abutments will be re-contoured and rock slope protection (RSP) will be placed on the downstream side of the bridge abutments, but nearly all of this bank stabilization will occur above the OHWM of Oregon Creek. The only instream work in Oregon Creek will be excavation of streambed and subsequent placement of 3 cubic yards (CY) of RSP within the OHWM channel near the toe of the abutments. This work will be done when flows are low. One CY of RSP will be placed in an erosional feature at the outfall of a culvert being replaced under Alleghany Road. The use of mechanized equipment to re-contour embankments, remove some of the upland riparian vegetation, and place RSP near the face of the abutments will result in temporary impacts on up to 0.010 acre of jurisdictional waters of Oregon Creek.

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