Santa Margarita River Fish Passage and Bridge Replacement: Final Design

This fish passage project on the Santa Margarita River, located two miles north of Fallbrook in north San Diego County, addresses a principal threat to endangered Southern California steelhead. This project will provide final design plans to remove an aging flood-prone box culvert structure that is a fish passage barrier, and replace it with a new 615 ft steel bridge over the Santa Margarita River that passes steelhead and 100-yr flood flow. This final design phase is funded by CDFW and is underway to generate the final design package and bid-ready documents for construction of the new bridge, complete CEQA according to San Diego County requirements, and perform pre-construction activities in preparation for anticipated implementation in fall 2021. The design work scope includes final bridge design review by San Diego County Public Works departments, agencies and stakeholders; supplemented with pre-construction project layout and construction documentation. The final design phase funded by CFDW culminates investment in prior design phases by CDFW ($165,000) and the State Coastal Conservancy ($507,000) over the past four years to advance design of the new Sandia Creek Drive bridge. The 90% plans released in December 2019 built on the 65% Basis of Design report released in March 2018 by the project design team KPFF (civil/structural engineering), River Focus (hydraulic engineering), Leighton (geotechnical) and Dudek (permitting), and partner Trout Unlimited.

This project delivers on a singular opportunity to restore fish passage from ocean to headwaters in a Southern California river in the next five years. The Santa Margarita River is a high priority river designated in the NMFS Southern California Steelhead Recovery Plan, in which fish passage barrier removal is one of the highest priority tasks for recovery. It leverages downstream fish passage work completed on Camp Pendleton, which remediated the only other barrier on the mainstem. Replacement of Sandia Creek Drive bridge will provide unimpeded passage for steelhead to historic habitat to the limit of anadromy 30 miles inland at the headwaters of this perennial river. The goals of this project are to provide endangered South California steelhead access to 12 miles of historic spawning and rearing habitat in the Santa Margarita River, and to promote resiliency to coastal communities along this largely undeveloped river — protected along its length by Camp Pendleton, The Santa Margarita Trail Preserve and the Santa Margarita Ecological Reserve. The Wildlands Conservancy (TWC), landowner on which the bridge will be built, is a valued and supportive partner for this project.

Developed through community engagement with private, state and federal funds, this project provides multiple benefits, and integrates endangered species protection into an urban landscape. This multi-benefit project will a) remediate a high priority fish passage barrier in a prioritized steelhead recovery river; b) improve trail user and traffic safety in the Santa Margarita Trail Preserve; c) protect the public from flood impacts of the existing Sandia Creek Drive bridge which overtops during heavy rainstorms; d) increase quality of riparian habitat for multiple threatened and endangered species; and e) preserve a critical wildlife migration corridor linking the Santa Ana and Palomar mountains.