Stevenson Bridge (23C0092) at Putah Creek Rehabilitation Project

The California Department of Fish and Wildlife (CDFW) has executed Lake and Streambed Alteration Agreement (EPIMS-SOL-56689-R3), pursuant to Fish and Game Code section 1602, to the project Applicant, Solano County Resource Management. The Project is limited to repairs to an existing bridge (including bridge superstructure, and foundation), construction of a permanent maintenance access road, and construction of a temporary creek crossing. The Project purpose is to rehabilitate the existing bridge to address seismic deficiencies, scour, cracks, spalling, and de-lamination, while maintaining its historical architectural features. The Project will also realign approximately 1,000 feet of the southern roadway approach to eliminate two sharp turns; realignment will occur outside of the channel and riparian zone. The existing bridge is 296 feet long and 24 feet wide with two piers within the channel, and abutments on each bank of Putah Creek. To conduct bridge repairs as they relate to Project activities and future maintenance on the bridge, a permanent access road composed of gravel will be constructed on the northeast side of the bridge. To access the bridge for repairs a temporary creek crossing and a clear water diversion will be installed in Putah Creek to isolate construction activities that occur within the creek. The crossing and diversion will be designed consistent with the Caltrans Construction Site Best Management Practices (BMP) Manual (Caltrans 2017) in accordance with Non-Storm (NS) Water Management BMP NS-4 Temporary Stream Crossing and NS-5 Clear Water Diversion. The Project will remove 22 riparian trees and 6 elderberry shrubs (Sambucus mexicana) within the riparian zone. Bridge rehabilitation will involve the following elements: 1) repair and replacement of the bridge superstructure (deck, drains, railings, etc.), 2) repair of the bridge foundation, including installation of two cast-in-drilled-hole (CIDH) pilings per pier and abutment (ten pilings in total), 3) replacement of the abutment retaining wall on the south side of the bridge, and 4) installation of rock slope protection (RSP) around abutments and piers for scour protection. Repairs of the existing bridge foundations will occur outside of the water or in de-watered areas. The access road will result in 10,019 square feet (0.23 acres) of permanent impacts to stream habitat associated with construction of the road. The clear water diversion and creek crossing will result in a total of 5,823 square feet (0.134 acres) of temporary impacts to stream habitat associated with installation of headwalls, pipes, the de-watered area for access to the piers, and the creek crossing. Bridge repairs will result in 548 square feet of impacts per CIDH piling resulting in a total of 5,480 square feet (0.126 acres) of permanent impacts to stream habitat associated with CIDH piling installation. Placement of RSP will permanently impact 436 square feet (0.01 acres) of stream habitat. The Project’s permanent impacts to stream habitat total 15,943 square feet (0.366 acres) and the temporary impacts to stream habitat total 5,823 square feet (0.134 acres).