PICO RIVERA, Calif. — More than 400 participants gathered Aug. 29 at the Pico Rivera Golf Club for the U.S. Army Corps of Engineers’ Whittier Narrows “Walk the Dam” event, trekking to the top of the San Gabriel Spillway amid hot summer conditions.
Along the route, which followed the San Gabriel River bike path, USACE employees handed out water, snacks and informational materials about upcoming dam construction, flood-resilience resources and facts about the dam. Children also received stickers, coloring books and trinkets.
The event gave participants a chance to ask questions and voice concerns directly with project staff as USACE expands outreach ahead of construction. The outreach is intended to inform residents about expected impacts along the dam’s three-mile span, including traffic changes, trail and park closures, and heavy construction. Work is scheduled for completion in 2033.
“It’s necessary; it’s vital that we do it,” said California state Sen. Bob Archuleta, who attended the event. “I’m just hoping everybody can take the noise, the dust and so on.”
“(USACE) has got it down,” Archuleta said. “They know what they’re doing, so we’re going to let them do their job and cheer them on because this is a great project for the Southern California region.”
Construction will strengthen features along the downstream slope of the dam, placing concrete steps along the slope and a berm at its base. The upgrades are designed to prepare the structure for worst-case conditions should it hold water far above its intended capacity for an extended period of time or even overtops.
The concrete steps serve as a contingency if the dam overtops, preventing water from eroding the earthen structure from the top down. Along the base, the berm protects against seepage if the reservoir remains at or near capacity for an extended period, keeping water from undermining the foundation.
Both measures aim to prepare the dam for unprecedented rainfall levels now identified as possible through modern forecasting methods that were not available when the dam was designed and completed in 1957. The Whittier Narrows Dam Modification Project team has identified worst-case scenarios that, while unlikely, can be addressed through proactive construction to help protect downstream communities like Pico Rivera.
As the most urban dam in the U.S. Army Corps of Engineers’ portfolio, the project requires careful coordination to ensure the modifications continue to protect the safety of downstream communities as it plays a key role in the Los Angeles County Drainage Area flood-risk mitigation system.
“Downstream of this dam we have 25 of the 88 cities in Los Angeles County,” said Aaron Smith, U.S. Army Corps of Engineers senior dam safety adviser. “They’re relying on this dam … about 1.25 million people between (here) and the Pacific Ocean.
“We want it to be here for hundreds of years to come, so the construction project that’s coming here today is going to help ensure that the dam is in place for future generations downstream,” he continued.
Community members were generally supportive of construction and the event itself, wanting to learn more about the project. Some voiced concerns about upcoming trail and park closures, while others wanted to learn more about possible detours. Projects like Whittier Narrows Dam provide opportunities for USACE to sublet federal lands to local cities and counties for recreational use, making community outreach a vital part of the project. USACE continues to involve local city governments and county officials in planning for construction impacts and the eventual return of leasing opportunities once construction is completed.
To learn more about Whittier Narrows Dam, the modification project and construction updates, visit https://wndsafetyproject.sec.usace.army.mil