American River History
Folscom Dam Modificiations
Folsdom Dam Raise
Folsdom Dam Bridge
In the News
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.