Devil’s Gate Sediment Removal to Begin in Spring

Residents can expect fewer truck trips over a longer time frame than initially planned, but the Los Angeles County’s Devil’s Gate Sediment Removal Project is expected to commence in earnest next April, according to Principal Engineer Keith Lilley, who spoke at Tuesday’s La Cañada Flintridge City Council meeting.
When the project was introduced in 2013, local residents expressed concerns about increased truck traffic, pollution and the potential harm to wildlife in Hahamongna Watershed Park.
Officials have attempted to adjust the proposal to mitigate some of those worries before sending it to the County Board of Supervisors for approval in August, Lilley said. If approved, 2.4 million cubic yards of sediment will be removed over a span of three to five years, with trucks making as many as 400 trips per day along La Cañada Flintridge streets near the worksite. The sediment will be hauled to landfills in Irwindale and Los Angeles.
“This is a project about protecting downstream communities from increased flood risk,” Lilley explained, adding that 1.3 million cubic yards of sediment entered the Devil’s Gate Reservoir following the Station Fire in 2009.
“The reservoir does not have adequate capacity for a major storm event,” he added, telling council members that the region “dodged a bullet” this year by avoiding the heavy El Niño rains that were predicted.
Three public informational meetings are being planned, Lilley said, including one in LCF that is tentatively scheduled for July 16.
Lilley said measures have been incorporated to lessen the local impact. Workdays will be limited to weekdays and will begin at 7 a.m. and end at 3:30, instead of at 7 p.m. The hauling also will be limited to the “dry months,” which could extend into November but will not include December.
Also, Lilley said, trucks will not stage on the surrounding streets and will proceed with covered beds. Trucks also will use new ramps into and out of the reservoir to pick up sediment, and will split time on routes leading either via the Pasadena side of the dam or on Berkshire Place, depending on the bell schedule of La Cañada High School across the street.
He also reported that only low-emission trucks will be used to haul sediment. What that means, Lilley told LCF Mayor Jonathan Curtis, is that they will meet 2007 emission standards.
“That sounds like the really old trucks, but over time, you get different standards,” Lilley said. “I think there’s a 2010 [standard] that’s starting to come into play, but those are not available for off-road dirt-hauling. And the difference in emissions is very similar.”
Lilley also said that plan has been altered to reduce the impact on wildlife in the area, characterizing some of the work that’s to be done as “habitat enhancement.”
“We’re going to remove the invasive species and do a lot of restoration,” he said. “We’re also going to focus on habitat restoration for birds, especially the least Bell’s vireo, an endangered species.”
All told, about 70 acres of habitat will be restored, and about 50 acres of that is to be perpetually maintained, Lilley said.
Furthermore, he said, the DPW never intends to conduct such a large-scale sediment removal project at Devil’s Gate again. “After the project, every year we’re going to come in and remove that sediment,” he said. “We won’t be in this position again, where we’re put over the edge by a large sediment inflow. This will allow us to manage annual smaller amounts of sediment and not go through another major sediment project like this in the future.”

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