This project replaced a low-flow river crossing at Sandia Creek Drive — the last remaining fish passage barrier on the mainstem Santa Margarita River — with a full-span bridge to restore migration access for endangered Southern California steelhead, opening 12 miles of upstream spawning and rearing habitat approximately two miles north of Fallbrook in San Diego County.
Location: Sandia Creek Drive crossing on the Santa Margarita River, approximately 2 miles north of Fallbrook, San Diego County. The Santa Margarita River is one of the last free-flowing perennial rivers in Southern California, flowing approximately 30 miles from headwaters at the Santa Margarita Ecological Preserve to the Pacific Ocean through Camp Pendleton.
Historical Fish Presence: Endangered Southern California steelhead (O. mykiss) historically used the full 30-mile extent of the river to the headwaters. The river is designated a high-priority recovery river in the NMFS (2012) Southern California Steelhead Recovery Plan. eDNA sampling during the project period also detected arroyo chub and Pacific lamprey. Riparian habitat supports endangered least bell’s vireo, southwestern willow flycatcher, and arroyo toad.
Project Lead: California Trout (CalTrout)
Project Partners: State Coastal Conservancy, San Diego County, The Wildlands Conservancy, California Department of Fish & Wildlife (CDFW), USFWS, Fallbrook Public Utility District, Fallbrook Trails Council, Trout Unlimited, KPFF Engineering
CFPF Funding: USFWS Grant No. F20AC00007 (administered via PSMFC). Total design phase cost: $1,176,060. Construction phase funding secured: ~$18M+ from WCB ($1.94M), CDFW FRGP ($2.378M), State Coastal Conservancy ($530K), CDFW Prop 1 ($7.2M), CNRA ($6M), and NOAA ($3.2M). Specific CFPF award amount not stated in available documents.
Project Description: The existing Sandia Creek Drive bridge was an aging, flood-prone low-flow box culvert crossing that acted as the last remaining fish passage barrier on the Santa Margarita River mainstem. Its removal and replacement with a full-span bridge was identified as a top priority in the NMFS steelhead recovery plan. Downstream barriers on Camp Pendleton had already been remediated, making this the final obstacle to unimpeded steelhead access to 12 miles of prime spawning and rearing habitat. This phase covered final engineering design (advancing from 65% to 100%), CEQA permitting, hydrological and scour analysis accepted by San Diego County Flood Engineering, CLOMR FEMA submittal, and preparation of a Major Grading and Improvement Plan. The replacement bridge was designed to withstand a 500-year flood event, eliminating a serious public safety hazard and improving access to the Santa Margarita Trail Preserve.
Expected Completion: Fall 2021 (Forum-funded design activities); construction began January 2023, with bridge completion targeted spring 2024.
Project Effectiveness: eDNA sampling at six sites during the reporting period detected O. mykiss, arroyo chub, Pacific lamprey, and bass in the Santa Margarita River. Construction was completed in 2024, removing the last mainstem barrier and providing steelhead access to the full 30-mile extent of the river to its headwaters. Cultural resource discoveries during construction led to a bridge alignment adjustment in coordination with tribal representatives and state and federal funders.
