The Los Angeles County Board of Supervisors voted July 7 to approve a settlement between LA County, the Arroyo Seco Foundation (ASF) and Pasadena Audubon Society (PAS) in a long-standing dispute over the sediment removal project at Devil’s Gate Dam in Pasadena’s Hahamongna Watershed Park. The settlement will reduce the negative impacts of the project and enable a more environmentally conscious approach that will protect endangered bird species that have been sighted within the area.

“We were never opposed to a sediment management program,” said Tim Brick, managing director of ASF. “The right approach was to have a slow, ongoing program of sediment management. We’ve been negotiating for the past year in order to get to a place that is mutually agreeable. Thanks to the wisdom of our attorney Mitchell Tsai, today’s result represents a major improvement in the county and provides greater flood protection with fewer negative impacts on the neighborhoods. We’re very pleased with the settlement because it has accomplished a lot that is very significant.”

PAS president Laura Solomon added, “We kept trying to explain to the county that we wanted to partner with them, not fight them. But they just ignored us, so we had to sue them. By working closely with natural resources and cycles of nature rather than treating the area like a big debris basin, we all feel this is a much better project than it was in 2014.”

Built in 1920, the Devil’s Gate Dam and Reservoir are in the Arroyo Seco Watershed, a 47-mile area that includes the cities of Pasadena, South Pasadena, La Cañada, unincorporated community of Altadena, as well as the Los Angeles communities of Hermon, Highland Park, Lincoln Heights, Montecito Heights, and Mount Washington.

Throughout the years, sediment has accumulated in the dam. The Station Fire in 2009, along with subsequent floods that occurred the same year and the following year, added more than a million additional cubic yards of sediment to the 2.7 million cubic yards that had previously built up over the years. Local residents opposed a controversial project known as the “Big Dig,” which was released by the Flood Control District and approved by county supervisors in 2014.

The project would have removed 2.4 million cubic yards of sand and sediment from the reservoir behind the dam over a three to five-year period. The county claimed the program would use low-emission trucks, but they intended to use 425 diesel trucks—the same ones that emit deadly black carbon. Since December 2014, two successful lawsuits have been filed by ASF and PAS to reduce the negative impacts caused by the Flood Control District’s $100 million mining and trucking program in the basin behind the dam.

“While the first lawsuit was settled in our favor in 2017, we weren’t content with all of the conditions, so we filed a second lawsuit with a tentative favorable ruling in June of last year,” Brick said. “At the time when county officials saw the tentative ruling, they decided it was better to settle with us than continue through another trial.”

The settlement will lead to shrinking the permanent footprint of the project by 20 acres, as well as restoration and establishment of additional riparian habitat in the Hahamongna Basin at the foot of the San Gabriel Mountains. The county and its habitat restoration contractor will also be required to purchase native plants and seeds from ASF as part of the settlement. Air quality emissions caused by the project will be reduced through the use of electric and compressed natural gas trucks to remove sediment.

“Other benefits have come out of this process that go beyond the excavation program,” Brick said. “We reduced a lot of the negative impacts of the project, in addition to providing for a more environmentally sensitive approach to the future. The settlement agreement will also result in an improvement in recreational values at the site. The county is going to partner with PAS to create a place where birders can enjoy watching rare species in their habitats that you normally don’t see in other parts of Southern California. The county will also urge the U.S. Army Corps of Engineers to complete an Arroyo Seco Watershed Ecosystem Restoration Study and request the U.S. Forest Service to complete a seismic and structural study of Brown Mountain Dam in the Arroyo Seco Canyon by April 2021. We’re pleased that this kind of cooperation and leadership are coming together.”


For more information, visit arroyoseco.org and pasadenaaudubon.org.