Update, Tour Give Corps’ South Pacific Division Better Picture of Whittier Narrows Dam Safety Modification Project

The commander of the U.S. Army Corps of Engineers South Pacific Division received an up-close look Jan. 18 at Whittier Narrows Dam and an in-depth update on the safety modification project designed to increase its capacity to handle extreme storms.

Col. James Handura, who assumed command of the division in November, was accompanied on the tour by Col. Andrew Baker, Los Angeles District commander; Col. Timothy Hudson, Tulsa District commander; David Hibner, SPD regional program director, and a range of subject-matter experts from both districts.

“We have a great team here on a project to reduce risk for community members,” Handura said.

The three-mile-long earthen embankment dam was constructed in 1957 and serves as a flood-risk management project that impounds stormwater from the Rio Hondo and San Gabriel rivers. Sitting about 11 miles from downtown Los Angeles in central LA County, the dam straddles the cities of Montebello and Pico Rivera. More than 1.25 million people in 25 municipalities live and work between the dam and the Pacific Ocean.

“The project has operated for 60-plus years as intended and has allowed those communities to develop in a way they would not have been able to otherwise,” said Aaron Smith, senior dam safety adviser with the Corps’ Huntington District, during a recent video interview. “In other words, they would have experienced flooding on an annual basis without that project.

The downstream side of the Rio Hondo portion of Whittier Narrows Dam is pictured Jan. 18 in Montebello, California. USACE PHOTO BY STEPHEN BAACK

“The project today is in good condition; however, the Corps of Engineers, through modern science and forecasting, has discovered a couple of deficiencies that are going to take significant modifications to make sure that it provides the same benefit it has for the past 60 years, for the next generation,” Smith said.

The Whittier Narrows Dam Safety Modification Study was completed in June 2019, and work has begun to address those deficiencies. Issues with the San Gabriel River spillway gates have already been addressed, which was one of the biggest factors driving the dam’s risk to the public, Smith said.

Remaining work includes placing soil cement on the crest and downstream slope of the embankment to protect against erosion and failure if overtopped and installing graded filter/drainage blankets and trench drains to control seepage. Minor construction started in 2021, with larger construction contracts to be awarded in 2025 after completion of design work. Major work is expected to take between four and five years to complete.

Unlike many dams in the Corps’ inventory, Whittier Narrows Dam is in a densely populated area, with thousands of people living, working and recreating nearby. According to Smith, the construction will not need to take up more space than they have right now, which he calls “a small miracle.”

The briefing and tour for Handura were led by Smith and his colleagues George Sunny, project manager, and Douglas Chitwood, lead project engineer for the SPD Dam Safety Production Center.

During the tour itself, Chitwood provided the lion’s share of the overview to Handura, describing the process of hardening the dam, installing filters at the toe of the dam, and working with local partners on road and utility modifications.

“I was extremely impressed with Col. Handura,” Chitwood said. “I’ve never talked to a commander who picks things up so quickly.”

Handura’s site visit was part of a larger trip to the LA District area of operations, during which he toured Prado Dam near Corona, California, to get updates on the Santa Ana River Mainstem project.