Folsom Dam Auxiliary Overflow Structure – Folsom, CA

folsom-overflow-1The Folsom Dam Auxiliary Overflow project is a 110 acre site located at the Folsom Dam in Folsom, CA. ATS has set up a 3,115 GPM Chitosan Enhanced Sand Filtration stormwater treatment  system. Due to the limited  amount of working area this site has some storage problems. To solve these problems ATS had to build 3 basins, which have a total capacity of 11.5 million gallons of water. This allows for pre-treatment and recirculation of the water when necessary. ATS utilized the spillway as a basin by placing a 24’ berm 300’ in length to give a 2.5 million gallon pre treatment area.


This is a four year project with the ability to treat up to 73 million gallons per year. The challenge of this project is, per spec, ATS cannot discharge to the American River which is downhill of the treatment system. ATS has to discharge treated water to Folsom Lake which is approximately 100 vertical feet up from the treatment system. This vertical rise took ATS over 2,500 feet of 16 inch pipe to reach the lake for discharge. This is an ongoing and active project and updates will follow.