Santa Anita Dam Spillway Modification


County of Los Angeles Department of Public Works

Project Location

Monrovia, CA

Project Cost



  • Construction Project Management


  • New Ogee Flood Spillway
  • New Emergency Generator and Power Upgrade
  • New Valves and Valve
  • Control System
  • New Shotcrete Armoring of Canyon Walls
  • 159 Acre-Feet Water Conservation Capacity
  • 500 Acre-Feet Groundwater Recharge
  • Probable Maximum Flood Capacity 

In order to meet the DSOD safety requirements, the Dam’s existing spillways were modified to accommodate a capacity to pass the Probable Maximum Flood estimation of 26,100 cubic feet per second in order to reduce the risk of dam failure from uncontrolled over-topping during major storm events. The new spillway allows floods to safely pass over the top of the Dam during an extreme storm event. Scope included upgrading the hoist system; replacing the Dam valves; strengthening the canyon walls near the spillway; replacing the garage/storage with a new garage and back-up generator; replacing the potable water system and electrical system; removing the Dam Operator’s house; constructing a helipad for emergency access; and installing new control systems and power lines to connect to a new electric entrance gate from Chantry Flats Road.

The project is partially funded by a California State Proposition 1E grant as well as funds from local agencies including the City of Arcadia, the City of Sierra Madre, and the Raymond Basin Management Board.

2021 ENR California Best Projects
Best Water/Environmental Project Southern California