Courtesy Photo | A diagram shows an overhead view of the Sacramento Weir fish passage structure,...... read more read more
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The U.S. Army Corps of Engineers has unveiled an environmental safeguard to protect endangered fish as part of the Sacramento Weir Widening Project. The system aims to prevent thousands of salmon and sturgeon from becoming stranded or blocked from reaching spawning grounds during flood events.
The fish passage, developed by the Sacramento District, is an innovative 1.6-mile "double hybrid technical fishway" connecting the Sacramento River to Tule Canal, which runs through the Yolo Bypass west of Sacramento. Unlike typical fish ladders, this system features two parallel channels designed for fish up to 10 feet long. Earlier designs with single-channel fish ladders were rejected after hydraulic modeling showed water would move too fast during floods for fish to navigate.
"This structure serves as a fish highway from the Sacramento River to the Tule Canal, and vice versa," said Robert Chase, senior fisheries biologist who recently retired from the U.S. Army Corps of Engineers Sacramento District. "It's about getting fish back on track where they need to go." Without this connection, fish would swim up the bypass with a good chance of stranding or potentially dying.
According to Chase, the fish passage is accessible after flood events when the fish passage gates are opened for water passage. These high-water events typically occur between December and March, coinciding with juvenile salmon migrating downstream while adult sturgeon move upstream to spawning grounds—an ecological cycle previously disrupted by existing infrastructure. A key component—the bypass transport channel—is already operational and has demonstrated remarkable effectiveness. During a recent event, this channel allowed juvenile Chinook salmon that were stuck in the basin to flush out, drastically reducing fish stranding compared to previous years when thousands of salmon would have been trapped.
"We're providing a state-of-the-art fish bypass structure," Chase explained.
This integrated approach includes sophisticated monitoring equipment like high-grade sonar cameras, hydroacoustic receivers, and passive integrated transponder (PIT) tag arrays—which Chase likened to the tags used for pets at the veterinarian. While the fish passage structure itself is the environmental protection measure that prevents fish mortality, these monitoring systems simply track and verify how well that protection is working. This technology will help researchers track fish movement and ensure the passage's effectiveness, providing valuable data on whether fish successfully navigate through the system and reach their spawning grounds in time, particularly for sturgeon headed to spawning areas near Red Bluff.
The project addresses critical challenges for threatened and endangered species protected under the Endangered Species Act, particularly salmon, steelhead, and sturgeon, explained Chase. These fish face significant obstacles in their migration, with flood risk management structures often causing fatal strandings.
"If some of these fish are held in a particular area for more than a few months, they unfortunately abort their spawn for the year," Chase noted. "Some of these fish only spawn every few years, so it's crucial to get them to their spawning grounds."
Developing this solution took nearly five years of intensive work, said Chase, involving multiple federal, state and county agencies, Architect-Engineering firms, and organizations including the U.S. Fish and Wildlife Service, National Marine Fisheries Service and California Department of Fish and Wildlife. The project faced unique design challenges because it needed to accommodate both salmon and sturgeon species simultaneously.
Chase brought expertise from previous work with the Bonneville Power Administration and USACE Walla Walla District in the Pacific Northwest. His experience with dams on the Columbia River that successfully pass both salmon and sturgeon proved invaluable to the design approach.
"There's never really been facilities that had to address both salmon and sturgeon," Chase explained. One of the biggest challenges was working without established design guidelines for sturgeon passage. Unlike salmon, which have well-documented passage criteria, no such standards existed for sturgeon.
The design team also had to carefully navigate regulatory requirements. To avoid classification as an "experimental design" that would have caused significant project delays, they negotiated with the National Marine Fisheries Service to implement comprehensive monitoring systems instead. This monitoring will not only verify the project's success but potentially establish guidelines for sturgeon passage criteria throughout the West Coast.
The project has already garnered significant interest from other water resource agencies, with the Sacramento District receiving frequent inquiries about incorporating similar designs into their facilities, noted Chase. Other agencies are particularly interested in the project's unique integration of flood risk management functionality with fish passage capability.
While the overall weir widening project is slated for completion in 2027, both the weir and the fish passage are expected to be operational by winter of 2026. The bypass transport channel is already complete and functioning as intended. After each fish passage operation following flood events, a science and engineering committee will evaluate the structure's performance and identify potential improvements.
The collaborative effort, estimated at approximately $350 million, involves the USACE, California's Central Valley Flood Protection Board, California Department of Water Resources, and the Sacramento Area Flood Control Agency. The flood risk management portion of the project includes a new 1,455-foot-long passive weir to supplement the existing 1,950-foot Sacramento Weir. This expansion of the weir and the creation of a bypass will allow excess floodwaters to overflow the Sacramento River channel and enter the bypasses during severe flood events, ultimately reducing the flood risk in the greater Sacramento region. This work is part of the larger American River Common Features 2016 project, which seeks to modernize Sacramento's aging flood risk management infrastructure.
"At the end of the day, everything fell into place," Chase said. "We got over the design hurdles, and now we have a solution that makes both engineers and biologists satisfied by providing flood risk management and fish passage."
The project represents a significant step forward in balancing human infrastructure needs with ecological preservation, offering hope for endangered fish populations in one of California's most critical river systems.
| Date Taken: | 06.17.2025 |
| Date Posted: | 06.17.2025 19:04 |
| Story ID: | 500908 |
| Location: | SACRAMENTO, CALIFORNIA, US |
| Web Views: | 91 |
| Downloads: | 0 |
This work, USACE Fish Passage Project Offers Lifeline to Threatened and Endangered Fish Species in California's Central Valley, by Grant Okubo, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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