Marsh Drive Bridge Replacement over Walnut Creek

Marsh Drive Bridge Replacement over Walnut Creek

Contra Costa County Public Works Department (CCCPWD), in cooperation with the California Department of Transportation (Caltrans), proposes to replace Marsh Drive Bridge (#28C-0442) over the Walnut Creek Channel (Project). The existing bridge is identified as structurally, seismically, and hydraulically deficient. The purpose of the Project is to replace the existing bridge to meet current design standards to provide safe public access. Project construction is expected to begin in fall 2021 or spring 2022 and take approximately 24 - 30 months to complete. The existing bridge was originally built as a 6-span concrete slab bridge in 1938, and was lengthened in the 1960s to a 10-span bridge. The bridge is currently 325 feet long by 34 feet wide. The new bridge will be designed to correct all of the existing bridge deficiencies and handle the seismic loads as well as the hydraulic flows within the channel. The proposed bridge replacement will be a 5-span bridge, pre-stressed concrete slab structure on concrete piles that is longer and wider than the existing bridge, at approximately 340 feet long and 55 feet wide. The bridge will be raised approximately seven feet with fewer supports in the channel to meet hydraulic standards. The proposed bridge will re-align Marsh Drive slightly to the north while utilizing a larger horizontal curve on the east in order to improve safety. To improve the roadway alignment and horizontal curve at the bridge, there will be approximately 350 to 500 linear feet of roadway approach work at each end of the bridge. In its final configuration the proposed bridge will accommodate two lanes of vehicular traffic (one in each direction) with pedestrian facilities on each side of the road. The Project will also include a separated path along the south side of the bridge that will tie into the existing Iron Horse Trail at the southeastern side of the bridge. The Project will use staged construction to avoid bridge closure and traffic detours. Two lanes of vehicular traffic (one in each direction) and a pedestrian access route will be maintained during each phase of construction. Standard traffic control will be used during construction. Work will occur in the creek and dewatering and/or stream diversion is anticipated. Ground disturbance will be necessary; depth will vary between Project elements. The maximum depth of excavation for Project work will be approximately 50 feet for the installation of foundation piles (using drilling), approximately 20 feet for bridge abutments and bents, approximately five feet for general roadway work, and approximately 15 to 20 feet for some utility relocations. Vegetation removal may be necessary throughout the Project area. Disturbed areas will be stabilized following construction. A public outreach presentation was held at the Buchanan Airport in December 2018.

Concord, Pacheco

Contra Costa