Settlement in Hahamongna Sediment Removal Case Could Come Today

The Los Angeles County Board of Supervisors will consider a settlement in the dispute between environmental groups and the county over the County Flood Control District’s Big Dig sediment excavation program at Devil’s Gate Dam in Pasadena’s Hahamongna Watershed Park.

The supervisors will review the settlement at its meeting on at 9:30 a.m. on Tuesday, July 7.

Beginning in 2014 the Arroyo Seco Foundation and Pasadena Audubon Society have filed two successful lawsuits since 2014 to reduce the negative impacts of the Flood Control District’s $100 million mining and trucking program in the basin behind Devil’s Gate Dam. Both of the lawsuits have led to favorable rulings by Judge James C. Chalfant.

The Devil’s Gate Reservoir Restoration Project is a four-year effort to increase flood protection for communities downstream of Devil’s Gate Dam and restore habitat within a popular section of the Arroyo Seco Watershed.

Los Angeles County Public Works plans to remove up to 1.7 million cubic yards of sediment from the reservoir that’s immediately behind the nearly 100-year-old dam.

The controversial project could last four years and eventually lead to hundreds of truck trips in and out of the Arroyo Seco daily. Known as the Big Dig, the project has come under fire by residents of Pasadena and nearby La Cañada Flintridge.

A large amount of sediment has not been removed from Devil’s Gate since 1994, when workers hauled out 160,000 cubic yards of soil and debris. An additional 1 million cubic yards of soil and debris were dumped into the basin by the Station fire in 2009, which burned more than 160,000 acres in Altadena, Pasadena, La Cañada Flintridge and Acton.

Devil’s Gate is the oldest dam constructed by the LA County Flood Control District, providing flood protection for the cities of Pasadena, South Pasadena and Los Angeles.

In addition to providing flood relief to communities that have endured nearly a decade of elevated flood risk along the Arroyo Seco, the project will also establish a permanent stormwater maintenance area that allows for the creation of 70 acres of enhanced habitat for wildlife and recreational opportunities for local communities.

The settlement that the Supervisors will consider on Tuesday is the result of legal rulings and long negotiations between the parties and will lead to shrinking the permanent footprint size of the project, verifying the use of the cleanest trucks possible moving the sediment, and restoring additional habitat in the Hahamongna basin at the foot of the San Gabriel Mountains.

Supervisor Kathryn Barger has recommended that the Supervisors approve the settlement agreement.