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

 

Increasing floodwater release capacity
Currently, the dam does not have sufficient outlet capability to make effective releases in preparation for one of these large storms. Releases through the existing eight outlets combined with releases through the powerhouse are limited to approximately 35,000 cubic feet per second (cfs). This is less than one-third of the capacity of the American River levees to pass floodwater. The levees can safely contain 145,000 cfs during flood operations. In order to make these large flood releases, the reservoir must be nearly 75 percent full and the water in the reservoir high enough to pass through the spillway gates near the top of the dam. By that time, the flood control space behind the dam is approximately 40 percent filled.

Folsom Dam Outlet Modifications

Enlarging the existing outlet gates and adding two new outlets will allow for larger releases of up to 115,000 cfs earlier during a flood event. This will create additional floodwater storage space behind the dam, which will, in turn, reduce the peak amounts of floodwater sent down the American River. The result is greater flood protection.

The existing eight outlet gates consist of an upper row of four gates and a lower row of four gates. The Corps and its partners began work in 2004. They plan to begin to enlarge the upper row of gates and to add two new gates to this row in the summer of 2005. The work will take approximately 6 years to complete and will be scheduled to allow Folsom Dam to continue at its current level of flood operation, water supply, and power service during construction.

In 2009, operations will begin to enlarge at least two of the lower outlet gates.

All Folsom Dam modifications are scheduled for completion in 2013.


 
   
   
n Reducing the Flood Risk
n Pre-Storm Flood Releases
n Folsom Dam Project Map
   
Releases through the existing eight outlets combined with releases through the powerhouse are limited to approximately 35,000 cubic feet per second (cfs). This is less than one-third of the capacity of the American River levees to pass floodwater.