Devil’s Gate Dam Sediment Project to Get Smaller

The so-called “Big Dig” won’t be as big after the Los Angeles County Board of Supervisors approved a scaled-down version of the Devil’s Gate Dam Sediment Removal project Tuesday.
Instead of the 2.4 million cubic yards previously approved for removal from the Hahamongna Watershed Park behind the Devil’s Gate Dam, now 1.7 million cubic yards will be scheduled to be removed over a three- to five-year span.
That’s still more than the 1.1 million cubic yards suggested in a plan set forth by the city of Pasadena and championed by environmentalists. Nonetheless, several speakers at Tuesday’s meeting expressed satisfaction about the compromise, which passed 5-0 after being proposed by L.A. County Supervisor Kathryn Barger at Tuesday’s board meeting.
“This amount offered by the supervisor goes a long way toward meeting the request of the City of Pasadena,” Mayor Terry Tornek said during public comments at Tuesday’s meeting. “We think the modifications go a long way toward satisfying the city of Pasadena’s request and I’m very grateful for it.”
Not everyone was quite so pleased.
“Supervisor Barger’s amendment moves in the right direction, but we’re still very concerned about the inadequacies of the mitigation program. You need to do more,” said Tim Brick managing director of the Arroyo Seco Foundation, which teamed with Pasadena Audubon to file suit and win a partial court victory in April.
That decision forced the L.A. County Public Works Department to revisit and recirculate portions of the Environmental Impact Report, the more ambitious version of which initially was approved by the Board of Supervisors in 2014.
The project was introduced about seven years ago. Following the 2009 Station Fire, storms sent 1.4 million cubic yards of dirt and rocks down the Arroyo Seco and into Devil’s Gate Reservoir, reducing its capacity to safely contain flood waters, the county said.
Four years after the state Division of Safety of Dams recommended removal of sediment behind the Dam to restore reservoir capacity and minimize flood risk downstream, the two environmental groups challenged the project in court. Superior Court Judge James Chalfant found the original EIR was deficient, but the judge did not reject the project, instead requiring the county to add some mitigation measures and reduce tailpipe emissions from trucks.
Still, La Cañada Flintridge resident Marnie Gaede took issue Tuesday with the fact that, even with the reduced amount of sediment hauled out, there will still be as many as 400 truck trips a day for as long as five years to remove it all.
“We’re constantly talking about the risk downstream,” she said. “But when you look at the other risk … the young people who are attending the nine schools down the street [from the project], there’s the diesel exhaust pollution that’s a known risk.”
She said the exhaust from the trucks — even those that are 2010 models or newer, as is required in the revised EIR — will increase cancer risks and asthma symptoms, among posing other health threats.
“I recognize this is a very difficult project for someone who lives in the area,” said Barger, who recently visited Hahamongna Park with Brick. “Unfortunately, Public Works … was not managing that dam, which is what got us into this position today.”
The modified plan also calls for coordination between the county and the city of Pasadena on stormwater capture and groundwater replenishment, as well as the development of an early warning system to notify downstream residents and businesses of any issues related to similar L.A. County Flood Control District facilities.
Supervisors also directed Public Works to coordinate with the Army Corps of Engineers on the completion of the Arroyo Seco Ecosystem Restoration Study, which is intended to identify opportunities for aquatic and riparian restoration along a 10-mile reach of the Arroyo Seco downstream from the dam.

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