Los Angeles County Public Works has begun the 2026 annual maintenance program at Devil’s Gate Reservoir, with contractor mobilization underway and truck hauling operations scheduled to continue through October, generating as many as 300 truck trips each weekday.
“The purpose of the annual maintenance activities is to reduce buildup of sediment in the reservoir maintenance area and substantially reduce the need for future, periodic large-scale sediment removal projects,” according to Los Angeles County Public Works.
Contractor staging began in late July. Truck hauling operations are scheduled Monday through Friday from 7 a.m. to 4:30 p.m., excluding holidays.
Trucks will travel west on Interstate 210 before continuing along Foothill Boulevard, Osborne Street, Glenoaks Boulevard and Sheldon Street to the Sheldon Pit in Sun Valley.
Trucks will return to the reservoir using the same route.
County officials said traffic volumes could reach as many as 300 truck trips per day during the hauling period. Public Works also said no changes have been made to the project’s Best Management Practices for 2026, with all safety and environmental protection measures remaining in effect throughout the maintenance activities.
Those measures include requirements to control dust, minimize noise where possible, maintain safe truck operations and protect surrounding habitat while work is underway.
The annual maintenance program follows one of the largest flood-control restoration projects ever undertaken in the Pasadena area.
In 2018, Los Angeles County launched a planned four-year effort to remove approximately 1.7 million cubic yards of sediment that had accumulated behind Devil’s Gate Dam over decades, much of it carried into the reservoir after the 2009 Station Fire stripped vegetation from the San Gabriel Mountains and increased erosion during subsequent storms.
The restoration project was designed to restore the reservoir’s flood-control capacity, which had been significantly reduced by decades of sediment buildup.
The work also included habitat restoration and improvements to long-term sediment management. Construction was substantially completed in 2021, about a year ahead of schedule.
Devil’s Gate Reservoir serves as a critical component of Los Angeles County’s flood-control system, capturing stormwater, mud and debris flowing down the Arroyo Seco before it reaches neighborhoods in Pasadena, South Pasadena and other downstream communities. Maintaining the reservoir’s storage capacity is considered essential to reducing flood risks during major winter storms.
County officials have said the current maintenance program is intended to prevent sediment from accumulating to levels that would once again require a massive excavation effort. By removing sediment and vegetation each year, Public Works aims to preserve the reservoir’s capacity while avoiding future large-scale removal projects that would require years of construction, extensive truck hauling and significantly higher costs.
Additional information, including project updates, hauling routes and maintenance schedules, is available through the Los Angeles County Public Works Devil’s Gate Reservoir project website.
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