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Corps, public talk about Whittier Narrows Dam modifications

Public Affairs
Published Sept. 13, 2013

PICO RIVERA, Calif. – The U.S. Army Corps of Engineers Los Angeles District held a public scoping meeting to comply with the National Environmental policy Act here Sept. 11 to describe potential structural modifications to Whittier Narrows Dam and to seek comments from the public on issues and concerns they wish to have considered during the preparation of its supporting Environmental Impact Statement.

Of particular interest were the impacts on environmental resources that might be significant without the implementation of mitigation measures. These resources include water quality, noise and vibration, air quality, socioeconomics and environmental justice, land use, recreation, visual and aesthetic resources, traffic and transportation, historical and cultural resources, vegetation and wildlife, and special status species.

The study and the EIS will identify and evaluate an array of remediation alternatives that include modifications to the downstream toe of the dam, raising the crest elevation of the dam, replacing a section of the embankment, modifying or replacing the spillway, and increasing the upstream storage capacity.

Following a presentation by project manager Kathy Anderson, project engineer Doug Chitwood and project environmental coordinator Debbie Lamb, attendees expressed interest in ensuring the Corps investigated potential impacts of higher water levels on the Whittier Narrows Nature Center, upstream residents, nearby industrial assets and local infrastructure. They also asked the Corps to consider how any proposed work would impact recreational facilities and whether environmental restrictions would adversely impact the schedule.

The Corps completed construction of Whittier Narrows Dam in 1957. It is an integral component of the Los Angeles County Drainage Area system of dams and channelized rivers, authorized by Congress in the Flood Control Act of 1936.

Whittier Narrows Dam is one of nearly 700 dams throughout the nation that are managed by the Corps. All were evaluated during a risk assessment program that began in 2005. Due to potential for overtopping and seepage-related failure modes, the Corps determined the dam could expose the downstream communities to unacceptable levels of risk in an extreme storm event. Corps officials stressed, however, that the level of concern is based primarily on the density of the population downstream there, and that there is no immediate danger of the dam breaching.