2013-17489. Notice of Intent To Prepare a Draft Environmental Impact Statement for the Whittier Narrows Dam Safety Modification Study Report

AGENCY:

Department of the Army, U.S. Army Corps of Engineers, DOD.

ACTION:

Notice of Intent.

SUMMARY:

Pursuant to the National Environmental Policy Act (NEPA), the U.S. Army Corps of Engineers, Los Angeles District (Corps) intends to prepare an Environmental Impact Statement (EIS) for the Whittier Narrows Dam Safety Modification Study (DSMS). Whittier Narrows Dam is located approximately 12 miles east of downtown Los Angeles, Los Angeles County, CA. The DSMS will evaluate alternatives to remediate safety concerns such as dam settling, seismic damages, and seepage. The DSMS will identify risk reduction measures that would be implemented to reduce life loss and property damage downstream in the event of a dam failure.

SUPPLEMENTARY INFORMATION:

1. Background Information. Construction of Whittier Narrows Dam was completed in 1957 as 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. After almost 60 years of settlement and damage from seismic events, the Corps has determined that the Whittier Narrows Dam has a high risk of failure due to significant seismic, seepage, and hydrologic issues. The DSMS and EIS would identify and evaluate alternatives to remedy these deficiencies. In the interim, the Corps has implemented several measures including: emergency management preparedness, remote monitoring, increased inspections, pre-positioning of materials for flood fighting, and updated flood mapping.

2. Preliminary Alternatives. The DSMS and EIS will identify and evaluate an array of remediation alternatives including: (1) Raising the crest elevation of the dam by 5 feet with a 5 foot high parapet wall on top of the crest; (2) constructing a weir in the embankment to allow smaller flood events to flow over the weir; (3) placing a fuseplug by taking out a section of the embankment and filling it with a concrete wall that would break at a lower elevation of water; and (4) removing sediment and deepening Santa Fe Dam Basin which is located upstream of the Whittier Narrows Dam to increase upstream holding capacity.

3. Preliminary NEPA Scope of Analysis. The EIS will also evaluate the impacts of alternatives on environmental resources. Resources initially identified in the NEPA scope of analysis as potentially significant without implementation of mitigation measures include, but are not limited to: 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.

4. NEPA Scoping Meeting: A public scoping meeting is preliminarily scheduled to be held in September 2013. The Corps will notify the public through local newspapers in advance of the meeting.

For Additional Information Contact: Questions or comments regarding the Whittier Narrows Dam DSMS, including requests to be placed on the mailing list may be submitted by mail to Ms. Deborah Lamb, U.S. Army Corps of Engineers, Los Angeles District, CESPL-PD-RL, 915 Wilshire Blvd., Los Angeles, CA 90017-3401; or by email to [e-mail].

DATES:

Submit NEPA scoping comments on or before 31 August 2013.

Dated: July 3, 2013.

R. Mark Toy,

Colonel, US Army, Commander and District Engineer, Los Angeles District.