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.