Thornton/Brady Storm Drain Project

Rainy season in the Thornton/Brady neighborhood of West Anaheim used to be downright dangerous due to deficiencies in the existing drainage system. Roads would flood. Residents would be trapped in their homes. Houses would get damaged. Trash cans would overturn and float away, leaving an unsanitary wake.

Those problems, like the flood waters, have receded. With the new Thornton/Brady Storm Drain Project, neighbors are protected against the devastation of 10- and even 25-year storm events.

Harris & Associates provided innovative engineering for this project, which included:

• Constructing the new storm drain system in the footprint of the existing "Thornton/Brady" concrete drainage ditch to minimize impacts to the neighborhood and the environment
• Design of a reinforced concrete box (RCB) storm drain in tight access conditions, i.e. between a 9-ft wide concrete drainage ditch, with a "V" invert at the surface to serve as a secondary/emergency overflow system to convey a 25-year storm event
• Design of a 28-foot long catch basin at the upstream end of the new system to collect approximately 50 cu ft per second where extreme ponding occurred

Core Elements

The preliminary drainage alignment was based on a previous study that recommended vacating the existing 9-ft wide concrete ditch and constructing new underground storm drain pipes in Thornton Avenue and in Brady Avenue, which would have cost the city approximately $2.9 million and required the acquisition of new rights of way. The Harris plan was different. It maintained, rather than abandoned, the existing drainage ditch and included:

• Design and construction of a 2,500-linear foot "customized" reinforced concrete box directly under the original ditch
• Provide flood protection levels for 25-year storm event (approx. 66,000 gal per minute) and 100-year storm event (approx. 82,000 gal per minute)
• Topographic survey 
• Utility-detection survey
• Geotechnical investigation
• Detailed traffic control plans

Harris' design of the new storm drain system not only protected residents from flooding, but also saved the city approximately $1.2 million.

Beyond the Blueprints

The creative approach eliminated acquisition costs for rights of way and reduced the city’s liability of flooding private properties by maintaining the historical flood path. But the most important payoff revealed itself with the arrival of the first big rains. "The new drain drank it all in," said one resident. "In the past we would have been completely overwhelmed and flooded out by such a heavy storm."