Bay-Delta Office

Fremont Weir Adult Fish Passage Modification Project

In 2018, Reclamation and the California Department of Water Resources (DWR) began the Fremont Weir Adult Fish Passage Modification Project to improve adult fish passage at the Fremont Weir and along the Tule Canal in the Yolo Bypass. The project constructed a new fish passage structure at Fremont Weir to widen and deepen the fish ladder and removed barriers in the Tule Canal.

• Project Overview
• Fremont Weir Factsheet
• Frequently Asked Questions

Overtopping Events & River Stage Data

• Sacramento River Weirs Overtopping (SacPAS)
• NOAA Fremont Weir Hydrologic Prediction

Videos

• Groundbreaking
• Fremont Weir Adult Fish Passage Modification
• Fremont Weir Upgrade Proves Successful in First Year

Fremont Weir

The Yolo Bypass is about 40 miles long, reaching from near Knights Landing down almost to Rio Vista The Fremont Weir, at the northern end of the Yolo Bypass, was completed in 1924. The weir is a 1.8-mile-long concrete structure designed to allow flow into the Yolo Bypass during high-flow events when the Sacramento River is higher than the weir's crest elevation. The weir has a concrete stilling basin just downstream of the crest and along its full length to minimize scouring during overtopping events. Once the Sacramento River recedes below the crest of Fremont Weir, fish are likely to become stranded in the stilling basin. California Department of Fish and Game (now known as California Department of Fish and Wildlife) constructed a 4-foot-wide, 6-foot-deep concrete fish ladder in 1965 (Figure 1). The ladder provided insufficient passage for adult salmon and did not provide passage for adult sturgeon. The project improves fish passage at the Fremont Weir and within the Tule Canal.

Figure 1 - Fremont Weir fish ladder installed in 1965

Figure 2 - Fremont Weir fish ladder replaced in 2018

Figure 3 – Former agricultural road crossing

Figure 4 – Former agricultural road crossing used to access land in the bypass and new crossing

DWR and Reclamation prepared the Initial Study/Environmental Assessment for the proposed Fremont Weir Adult Fish Passage Modification Project in 2017. Reclamation signed a Finding of No Significant Impact (FONSI) on July 14, 2017.

• Fremont Weir Adult Fish Passage IS/EA & FONSI

The project was part of the original Yolo Bypass Salmonid Habitat Restoration and Fish Passage Project and was identified to be included in California EcoRestore in 2015. For more information related to the Yolo Bypass Salmonid Habitat Restoration and Fish Passage Project and EcoRestore projects in the Yolo Bypass, visit DWR's web page.