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American River Common Features Folsom Dam Modifications Folsom Dam Raise Folsom Dam Bridge

Slurry Wall
A slurry wall is constructed by excavating a 3-foot-wide trench up to 80 feet deep along the length of the levee and filling the trench with slurry, which is a mixture of soil, cement, clay and water. Once hardened, the slurry mixture creates a watertight barrier to prevent seepage through and under the levees during a high flood event.

The 19 miles of slurry wall constructed so far on the American River are much deeper than originally designed. Seepage through the levees was the main concern following the record flood of 1986, and engineers planned slurry walls up to 30 feet deep to control this through-levee seepage. High river flows in the near-record storms of 1997 caused floodwater to seep under the levees and pointed to the need for deeper slurry walls to control this under-levee seepage. As a result, slurry walls are now as deep as 80 feet.

After the floods of January 1997, the Corps and its partners reassessed the levee strengthening design because of damage to levees previously believed to be strong. As a result, they revised the levee designs to include deeper slurry walls and to completely cut off the gaps near bridges and deep utility line crossings. This work will ensure that the levees can safely pass flood events much higher than the record 1986 flood.

General Site Conditions along the American River


n Levee work
n Jet grouting
n Common Features Project Map
High-Pressure Drill
A high-pressure drill injects slurry mix into the levee.