Marsh Creek Rd. Bridge Replacment (28C-141) 0662-6R4079 and CP#15-39

Marsh Creek Rd. Bridge Replacment (28C-141) 0662-6R4079 and CP#15-39

The project consists of bridge replacing; the proposed bridge would be an approx. 90 ft. long, single-span bridge. The bridge deck would be widened to provide a width of approx. 43 feet, with 12-foot wide travel lanes, 8-foot wide shoulders, and an approx. 1.5 foot wide concrete barrier on each side of the new bridge. The proposed bridge would be constructed of reinforced concrete on pre-cast and pre-stressed I-girders. The reinforced concrete bridge abutments would be supported by spread footings. The existing structure includes tall, reinforced concrete walls that restrict the flows of Marsh Creek under the bridge. These existing walls would be removed as part of the project to open up the channel where Marsh Creek flows under the bridge. The channel work would require that Marsh Creek be dewatered in accordance with regulatory permits. Dewatering would likely be accomplished using coffer dams according to methods acceptable to the CDFW. Water would be routed around the work area to maintain downstream flows. Dewatering would occur in the work area extending approx. 150 feet upstream and 200 feet downstream of the existing bridge. Along with replacing the bridge, , the horizontal alignment of Marsh Creek road would be shifted north on a parallel alignment to accommodate the wider bridge structure, and earthwork would be required along both sides of existing roadway. In order to meet the hydraulic design standards, the vertical profile of the bridge would be slightly raised. The changes in both the horizontal and vertical alignments require reconstruction of Marsh Creek Road on both sides of the existing roadway. In order to meet the hydraulic design standards, the vertical profile of the bridge would be slightly raised. The changes in both the horizontal and vertical alignments require reconstruction of Marsh Creek Road on both sides of the bridge. (900 feet total). Two retaining walls may also be necessary: the first retaining wall would be along the north side of the roadway (west of the bridge), would have an average approx. height of 10 feet, and would be 183 feet long; the second smaller retaining wall would be set back from the roadway on the north side of the road and would be approx. 7 feet high and 90 feet long. The final design of these walls will be determined prior to construction. The widening and realignment of Marsh Creek Road to construct teh new bridge may require right of way or temporary easements from several adjacent parcels. Staging of construction materials and equipment would occur in two potential locations north and south of the road in the center of the project site. The northern staging area would occur within an undeveloped vegetated area, and the southern staging would occur entirely within paved parking areas. Standard construction equipment would be used for constructing the proposed project, including but not limited to: excavators, graders, scrapers, loaders, sweepers, /scrubbers, plate compactors, rollers, backhoes, and pavers. The proposed project has been designed so that existing traffic can be accommodated during construction, while minimizing impacts to the surrounding right of way, including existing buildings. Construction would be sequenced in a manner to minimize traffic impacts during construction. Two phases of bridge construction are expected: the first phase would partially construct the new bridge with traffic using the existing bridge; The second phase shifts both directions of traffic onto the new bridge so the existing bridge can be demolished and the new bridge can be built to full width. During construction, the project is expected to accommodate one 12-foot wide travel lane in each direction on Marsh Creek Road though the project site throughout construction, with short, infrequent periods of one lane traffic controls. Construction would take up to two seasons, likely starting in the summer of 2017 and finishing by the fall of 2018, pending Caltrans and Federal approvals. utility relocation and right of way transaction will be necessary in support of the project. Tree and shrubbery removal and trimming will be necessary, in order to minimize damage to trees, any roots exposed during construction activities will be clean and cut and tree branches will be trimmed.

Clayton

Contra Costa