ASF Logo

Arroyo Seco Foundation

News of the Arroyo


FCD and environmentalists face off over “Big Dig” at Devil's Gate


Case to be heard in January




<b>January 15, 2017</b> - Bill Christian provides an incisive overview of the battle over sediment management behind Devil's Gate Dam in Hahamongna Watershed Park.


Bill Christian, Director, WPRA


West Pasadena Residents Association Newsletter


Having virtually neglected sediment accumulation in the basin behind Devil’s Gate dam over the past two decades, the LA County Flood Control District (FCD) expects to move forward — absent an unfavorable court decision or pre-trial settlement — with what it believes is an urgent and necessary sediment removal program. The Arroyo Seco Foundation and Pasadena Audubon challenged that vision in December 2015 by jointly filing a suit to force the FCD to modify its plan. The case is slated to be heard in January.

Looking back

Devil’s Gate Dam was built in 1920 as a part of a massive County flood control
program following major destructive floods in 1914 and 1916. Named for a nearby rock outcropping that, say some, resembled the face of a devil, Devil’s Gate was the first debris dam in Los Angeles County.

Twenty years ago, Pasadena established the Hahamongna Watershed Park
as a commitment to protect our rich environmental and water resources for future generations. Pasadena also encouraged the County to rehabilitate Devil’s Gate Dam, which had been condemned after the 1971 Sylmar earthquake, and to operate it in a way that would be compatible with preservation and restoration of habitat, wildlife and recreational opportunity in the basin.

A key to achieving those lofty goals, however, was implementation of a continuous sediment management program to provide flood protection, but avoid massive disruptive events, such as the “Big Dig,” every few decades. Sadly, the FCD has not removed any significant quantities of sediment since 1994.

The “Big Dig”

The current massive FCD plan would extract and ship out over local roads and freeways about 2.4 million cubic yards of sediment over four years and require 400 diesel-truck round trips be made each day. Opponents insist this plan would degrade our air quality, raise noise levels for nearby schools and neighborhoods, choke traffic on the 210 freeway and other streets, cripple recreation in the Hahamongna watershed area, and permanently destroy important and rare riparian habitat behind the dam, which shelters sensitive and listed species.

City and others oppose FCD plan

The City of Pasadena also expressed its opposition to the FCD plan by establishing the Sediment Working Group (SDG), chaired by Dr. Seema Shah-Fairbank of Cal Poly Pomona, to review the County’s plan and its effects. The SDG recommended a smaller, slower and more careful approach. For
example, instead of more than 400 truck trips per day, the SDG recommended only
120. The SDG also recommended reducing the size of the County’s permanent footprint in the basin and including a seasonal lake. City Council unanimously endorsed the SDG recommendations. And despite timely entreaties by the City, the FCD has to-date ignored Pasadena’s proposal. The WPRA has also twice expressed opposition to the current FCD plan, firm in its belief that the Arroyo Seco and the Hahamongna watershed areas are Pasadena treasures — irreplaceable players in the continual recharging of our aquifers.

Big Dig could complicate relook, restoration

Pasadena Mayor Terry Tornek recently proposed the City take an integrated
relook at the Arroyo Seco to develop a new vision for how the Arroyo is used, managed and governed. That relook would include an assessment of the Arroyo’s current and future values to the community. The LA County Flood Control District approach to sediment removal at Devil’s Gate Dam would necessarily and significantly short-circuit Mayor Tornek’s plan and, quite likely, interrupt other governmental planning efforts, including a comprehensive Arroyo Seco restoration plan currently led by the US Army Corps of Engineers.

Bill Christian

For more information about the alternative sediment removal plan, visit the City’s and the Arroyo Seco Foundation’s website.




Arroyo Seco Foundation, PO Box 91622, Pasadena, CA 91109-1622 (323) 405-7326