Prado Flood Control Basin Upgrades

Riverside County, California

General Contractor: Yeager-Skanska
Contract Value: $5.4M
Year Completed: 2005
Scope of Work: Plumbing
Services: Design Engineering, Fab, Install
Delivery: General Contracting


The U.S. Army Corps of Engineers and the Orange County Flood Control District awarded the $67-million contract to Yeager Skanska, Inc. in lieu of the Santa Ana Mainstem Project to raise the height of the dam 28.4 ft, construct a new intake tower, and improve the structure’s outlet works. The work constitutes the first of three stages overall of modifications planned for Prado Dam. Two subsequent phases involved constructing dikes within the dam’s basin to protect property from flooding and raising the dam’s spillway by 20 ft. The dam’s reservoir increased from 6,695 to 10,300 acres, boosting its capacity at the spillway’s crest from 217,000 to 362,000 acre-ft. At the same time, the dam’s crest was lengthened from 2,280 to 3,050 ft, and its outlet capacity increased from 9,000 to 30,000 cfs. When completed, it will handle what is called a 200-year flood.

The outlet works comprise an approach channel, a regulating intake structure, a transition structure, a stilling basin, and a downstream channel. The regulating intake, a concrete structure 144 ft wide by 90 ft long, will have a trash rack, six intake passages, and a 36 in. diameter bypass pipe on each side for low flows. An 82 ft high control tower houses controls for remotely operating the gates and also monitors instrumentation, a mechanical room, and an elevator for access to the gate room. Water entering the six intake passages passes through a 213 ft long transition structure that directs flows into two conduits before emptying into a stilling basin and finally into the downstream channel. 

Some info courtesy of