Trinity River Bridge Scour Rehabilitation

Trinity River Bridge Scour Rehabilitation

Caltrans District 2, proposes the following activities (scope of work) to retrofit the bridge: 1) Import clean gravel to construct temporary gravel work pads around each pier, and to place in the river, as necessary, to construct temporary stream crossings to access piers 2, 3, and 4 (piers being retrofitted). To construct the gravel work pads, is likely that gravel will be placed out into the channel unit the work pad has been built up. If a cofferdam is needed to support the gravel pad, then sheet pilling will be driven around the wetted perimeter of the gravel work pad. 2) Temporary work pads will most likely be constructed in one, or both, of two ways: a) temporary stream crossings would likely be constructed by placing culverts in the stream and covering them with gravel to enable construction equipment to access each pier needing retrofit. And or b) by constructing a temporary trestle work platform where piles are driven into the stream and a platform is constructed above the piles. Minor streambed grading, under the structure, may be necessary to allow head room for equipment. 3) False work will be used to support the new bent cap to each pier during construction. The term "false work" refers to the temporary supporting system between the ground and the bridge soffit. 4) New outrigger bents, supported on large diameter cast in drilled holes (CIDH) pile shafts, will be constructed. The holes are approximately 5 feet in diameter and 80 feet deep and will produce approximately 350 cubic yards of material that will become property of the contractor. Upon completion of the piers, the three existing piers and footings will be removed and the seal course will be removed, within 3 feet of original grad. Removal of the existing piers will lessen the permanent impacts to the Trinity River.

Trinity

California Department of Fish and Wildlife, Northern and Eureka Region 1 (CDFW), California Department of Parks and Recreation, California Highway Patrol, California Native American Heritage Commission (NAHC), California Regional Water Quality Control Board, North Coast Region 1 (RWQCB), California State Lands Commission (SLC), Department of Toxic Substances Control, Department of Water Resources, Office of Historic Preservation, Resources Agency

Transportation:Other (Retrofit Bridge Scour)

Biological Resources, Hazards & Hazardous Materials, Hydrology/Water Quality