Rock Slough Intake and Fish Screens

Contra Costa Water District provides most of the municipal and industrial water supply to the East Bay area of Northern California. Its three large-surface water intakes in the Sacramento-San Joaquin Delta have a combined raw water capacity of 1,200 cfs. The largest, Rock Slough, was completely rebuilt in 2010–2011 by the U.S. Bureau of Reclamation using funding from the American Recovery and Reinvestment Act of 2009.

During commissioning of the intake and fish screens, the U.S. Bureau of Reclamation (USBR) and Contra Costa Water District discovered that the four fish screen cleaners would not effectively clean the screens of the heavy debris loading. The screen cleaners wouldn’t properly collect and dump debris, causing the system to trip alarms and go offline. This was especially problematic since the project was near completion and out of budget, and liquidation damages would be assessed to the general contractor within three weeks.

In a period of 10 days, Schnabel visited the site, designed, fabricated, delivered, installed, and tested a new prototype screen cleaner that has been in operation since November 2011. Since then, we have provided on-call engineering services to support Contra Costa Water District with a variety of tasks. Work has included designing new screen cleaners for the 320-ft-long by 20-ft-high fish screens; troubleshooting hydraulic power system issues and designing an offline style oil-to-air heat exchanger system; designing two access boat ramps; participating in a USBR value engineering study; designing mooring anchors and lines for the relocation of an existing debris boom; and retrofitting existing ultrasonic level sensors with stilling wells.