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American River Common Features Project
The American River Common Features Project involves significant levee improvements on the American River and Sacramento River, as well as in the Natomas area. When completed in late 2004, the work on the American River levees will reduce a portion of the Sacramento area’s flood risk to 1 chance in 100 in any given year. Additional work has been completed on Sacramento River levees and in the Natomas Basin, and more levee work is in the planning stages for these areas.

The American River Common Features Project is part of the integrated Watershed Project to reduce the risk of flooding in the Sacramento area to a 1-in-213 chance in any one year. This overall effort also includes modifications to the outlet gates at Folsom Dam and the Folsom Dam Raise.

Soon after the record storm of 1986, the Army Corps of Engineers (Corps), California Reclamation Board (Reclamation Board) and the Sacramento Area Flood Control Agency (SAFCA) formed a partnership to find ways to reduce Sacramento’s flood risk.

At one time the Corps, Reclamation Board, and SAFCA proposed a flood control dam near Auburn along with the levee improvements downstream of Folsom Dam. There was no community consensus for the dam, and Congress told the Corps to focus instead on the downstream flood control system, and to combine a number of features common to three different flood management proposals into one plan to reduce the flood risk to Sacramento.

The result is the American River Common Features Project, a comprehensive effort that includes levee work on the Lower American River, levee work on the east bank of the Sacramento River adjacent to downtown, levee work in the Natomas Basin, additional upstream river flow gages, and an improved flood warning system along the lower American River.

These common features are an interim measure to reduce the flood risk. Future measures include modifying the outlet gates at Folsom Dam and raising Folsom Dam so that it can hold back additional floodwater.

Authorized elements
The main element of the originally authorized common features project was to install an impervious barrier along almost 20 miles of American River levees. The barrier consists of a mixture of soil, clay, cement, and water, called a slurry cut-off wall. Other elements include:

  • Installing additional stream flow gauges along the upper American River to more accurately assess flows into Folsom Reservoir.

  • Improving the network of sirens used to warn people of potential flooding along the lower American River.

  • Raising the left bank of the non- Federal levee upstream of the Mayhew Drain by an average of 2.5 feet for a distance of 4,500 feet.

  • Raising the right bank of the American River levee by an aver- age of one foot from 1,500 feet upstream to 4,000 feet down stream of the Howe Avenue Bridge.

  • Modifying the south levee of the Natomas Cross Canal for a distance of 5 miles to ensure that the south levee level of protection is consistent with that provided by the authorized levee along the east bank of the Sacramento River.

  • Modifying the north levee of the Natomas Cross canal for a distance of 5 miles to ensure that its height is equivalent to the height of the south levee.

  • Installing gates to the existing Mayhew Drain culvert and pumps to prevent backup of floodwater on the Folsom Boulevard side of the gates.

  • Installing a slurry wall in the north levee of the American River from the east levee of the Natomas East Main Drain upstream for a distance of approximately 1.2 miles.

  • Installing a slurry wall in the north levee of the American River from 300 feet west of Jacob Lane north for a distance of approximately one mile to the end of the existing levee.



Levee work

Slurry wall

Jet grouting



US Army Corps of Engineers Sacramento District

The Reclamation Board
State of California

Sacramento Area
Flood Control Agency

A city dealing with its flood risk

After more than 150 years of struggling to keep the American and Sacramento Rivers out of their homes and businesses, the people of Sacramento now have comprehensive plans in the American River Common Features, Folsom Dam Modification, and Folsom Dam Raise projects to reach the level
of flood protection an important city such as Sacramento must have.

Project costs

Since the record floods of 1986, engineers have developed more sophisticated tools for collecting information on storms and on the effects of high flows on levees, as well as methods to analyze this information. Flood control engineers today know much more about the conditions of the American and Sacramento River levees and how to strengthen them than when they started their efforts to reduce Sacramento’s flood threat several years ago. The benefit of these advances is better flood protection. The most significant of these advances is deeper slurry walls, jet grouting, and stronger levees. As the engineers learned more about the flood control system so critical to protecting the people of Sacramento, they also saw the amount and cost of the work to protect the community increase.

Costs for the project changed mainly as a result of improvements in technology, newer methodologies, and due to an increase in the amount of work. When Congress authorized the levee improvement work in 1996, the Corps estimated the cost at $56.9 million. In 1999, Congress authorized additional work increasing the estimated cost to $91.9 million. The Corps and its flood control partners now estimate that it will cost $205 million to accomplish the levee work needed to reduce Sacramento’s flood risk.