Feather River Setback Levee

Few places in the State of California have flooded as often and as significantly as Yuba County. In 1986 a levee break on the Yuba River destroyed hundreds of homes, properties and businesses. A subsequent flood in 1997 was even more devastating and caused the death of 3 people and hundreds of millions of dollars of property damage. In 2008, TRLIA embarked on the Feather River setback levee, which was a key component of their $400 million levee improvement program to provide the area with a 200-year level of flood protection.

This immense project brought together private citizens and local, state and federal agencies to cooperatively and innovatively expedite financing and construction. In addition to providing the basin with increased flood control, the setback levee also helped restore the river and the surrounding riparian vegetation and habitat. In 2009 this project won the Flood Control Project of the Year by ASCE.

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Key Facts

Helped provide 200 years level of flood protection
Earned 2 awards from ASCE
5 miles of up to 75 ft. deep cutoff wall
Feather River Setback levee cutoff wall excavation | GEI
Cutoff wall excavation
big puddle of water in middle of dirt
trucks around a tall hill of dirt
trucks hauling dirt
rocky road
pumps around water surrounded by rocks

Key Challenges

The project posed a significant design challenge as the setback levee had to be constructed on a foundation composed of highly-variable, soft and pervious streambed deposits, and required various methods of seepage control to maintain integrity. The project team performed extensive geological and geotechnical investigations, which were used to refine the alignment of the new levee and locate it on an older, more consolidated soil formation wherever possible. Ultimately, to control underseepage, about five miles of soil-bentonite slurry trench cutoff wall (up to 75 ft. deep) was constructed integral with the levee structure, and 26 relief wells were installed in areas where deep, recent, alluvial soils could not be avoided.

The project team demonstrated resourcefulness in planning and solving design challenges throughout the project. During the course of construction, numerous obstacles were encountered, sometimes requiring the team to modify the levee alignment. This was the case in the unexpected discovery of an ancient Native American burial ground. The project team worked with state and local officials to develop a modified design that would preserve these cultural remains, maintain the integrity of the original design, and not impact the completion schedule.

Another challenge the team encountered during construction was the increased requirements for federal permitting. Due to the devastation by Hurricane Katrina, the Corps changed the federal authorization process, and the updated process required preparation of an environmental impact statement (EIS) that wasn’t in the original plan. The project schedule could not accommodate the several-year process that a typical EIS takes, so the team worked with the Corps to streamline the permitting process such that it was completed within ten months. In order to partially offset the delays in obtaining the federal permits, the team worked cooperatively with federal and state regulators to begin working on 80 percent of the setback levee that was not impacted by the federal permits. This construction occurred in parallel with the federal permitting process.

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We’ve always said that we have the best professionals in the business working on this project. As a result, we also have the strongest flood protection in Northern California.

- Mary Jane Griego, Former Yuba County Supervisor, Former Chair of the TRLIA Board