Sacramento Weir expansion construction delayed one year due to structural settlement issues

California Construction News staff writer

Parts of the historic Sacramento Weir are sinking unevenly, a problem that officials say will push back the completion of the flood-control expansion by about a year.

The U.S. Army Corps of Engineers (USACE) confirmed that vertical settlement exceeding design tolerances was detected in early 2025 at the north abutment wall of the Sacramento Weir Expansion. The 109-year-old weir, located about four miles upstream from Tower Bridge on River Road, was originally built in 1916 and currently has 48 manually operated gates to manage river flows.

The north abutment wall is one of 26 supports for a future bridge along the overall expansion project. USACE said subsurface investigations are underway to better understand slope soil movement so the wall can be rebuilt safely. “Addressing the unexpected movement is expected to delay project completion by about one year, but the current Sacramento Weir remains fully operational and there are no impacts to public safety,” the agency said.

As a result, the expansion, which is widening the 1,950-foot weir by an additional 1,455 feet to allow more floodwaters from the Sacramento and American Rivers to flow over into bypasses, is now expected to be completed by 2027. Final site cleanup and erosion-control planting will continue through 2028.

Granite Construction was awarded a $173 million contract in 2023 and is working with Con J. Franke Electric, a local electrical contractor responsible for utility relocation, constructing a utility building, and installing a modern fish passage system. The project will widen the existing 1,950-foot weir by 1,455 feet to allow additional floodwaters from the Sacramento and American Rivers to flow over the weir and into bypasses.

The Sacramento Weir Widening Project, led by USACE’s Sacramento District, in partnership with the Sacramento Area Flood Control Agency, the Central Valley Flood Protection Board, and the California Department of Water Resources. The project is being constructed in two parts: the Sac Bypass Widening project, managed by the California Department of Water Resources, and the Sacramento Weir Widening Project, managed by USACE.

“Large, complex infrastructure projects often require adjustments due to real-world conditions that may not align with initial predictions,” USACE said in a statement. “While we conduct subsurface investigations and analyses following industry standards and best geotechnical practices, unforeseen variations can still occur. At the north abutment, the underlying soil has responded in a manner that differs from the original design assumptions.”

USACE provided a detailed timeline of the north abutment wall work:

• January–February 2025 – Routine monitoring; movement remained within design tolerance.

• March 2025 – Movement exceeded tolerance limits, prompting evaluation.

• Spring–Fall 2025 – Engineers study the issue and design a solution.

• 2026 – Finalize cost estimate, construction schedule, and begin corrective work.

• 2027 – Complete corrective work.

Despite the delay, USACE emphasized that the project should remain within budget and that the weir continues to provide essential flood protection for farms and communities in the Sacramento region.