It’s Not “The Big Dig,” But Devil’s Gate Dam Sediment Removal is Underway

The annual removal of sediment from the Devil’s Gate Dam in Pasadena began last week on an interim basis as the county makes preparations for storm season.

Los Angeles County will be hauling the sediment temporarily to Johnson Field while green waste will be taken to Scholl Canyon Landfill at a rate of no more than 10 trucks per day, officials said.

According to a statement, about 3,000 cubic yards of sediment will be removed over the span of four weeks, a measure similar to previous projects on the basin completed in the summer/fall of 2015.

Keith Lilley, the Senior Civil Engineer at the Water Resources Division of L.A. County Public Works, said this removal is simply a yearly touch up and does not signal the start of the so-called “Big Dig” project — which is a plan to excavate 2.4 million cubic yards for flood management purposes, a plan that has been met with resistance from local activists.

The multi-year plan would eliminate certain native habitat areas, but replace and rejuvenate them by removing non-native plants that are already clogging and affecting the natural areas around the dam, and re-growing native plant species.

“Every year, we remove what comes and settles in front the valves,” Lilley said. “We do that to keep the valves clear. What you’re seeing is annual minor maintenance before this storm season.”

The original plan by the L.A. County Flood Control District was met with opposition by the Pasadena Audubon Society, among others who believe the project would endanger the natural habitats of wildlife in the area and disturb neighborhoods. In 2014, they filed a lawsuit against the county along with the Arroyo Seco Foundation.

“The county has applied for an incidental take permit on the Least Bell’s Vireo, a federally protected an endangered bird. We now don’t understand why they need to take out 2.4 million cubic yards of dirt when before 1.67 million cubic yards of dirt was fine,” said Laura Garrett, the audubon society’s chair.

However, according to a presentation made earlier this July by Lilley, the plan needs to move forward because the Devil’s Gate basin is naturally vulnerable to flooding.

Lilley said the reservoir does not have adequate capacity for a major storm event. If such a storm were to come about, Public Works estimates that flooding would occur in many places — including Pasadena, South Pasadena and Los Angeles — and would require the 110 and 5 Freeways to shut down.

Lori Paul, a local biologist and Pasadena resident who is opposed to the project, said the possibility of a major storm causing widespread flooding is due to decades of band land management

“Mother Nature has been in quality control and product development for millions of years longer than we have. We’re paying millions of dollars to take out accumulated sediment here, when we are also paying millions of dollars to truck in sediment down at our beaches….this is absurd, Paul said. “The system of the mountains is supposed to work by bringing sediments down and sluicing them in various sizes to form stream sites and riparian habitats all the way down to the beach.”

For continuing updates on the status of these projects, please click the headline or contact Steve Sheridan of Public Works’ Flood Maintenance Division East Area Office at (626) 445-7630.