2010-2510. Notice of Intent To Prepare a Draft Environmental Impact Statement and Dam Safety Assurance Program Modification Report for the Isabella Dam Project, Kern County, CA

AGENCY:

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

ACTION:

Notice of intent.

SUMMARY:

Pursuant to the National Environmental Policy Act of 1969, as amended, the U.S. Army Corps of Engineers, Sacramento District (Corps), in cooperation with the U.S. Forest Service, Sequoia National Forest, intends to prepare a draft Environmental Impact Statement (EIS) for the Federal action to remediate seismic, seepage, and hydrologic dam safety concerns at the Isabella Lake main and auxiliary dams. Isabella Lake is located on the Kern River approximately 45 miles northeast of Bakersfield, Kern County, California. The proposed action is being conducted through the Corps' Dam Safety Assurance Program (DSAP) for the evaluation of existing dams.

ADDRESSES:

Current and archival information regarding the Isabella Lake DSAP Project can be obtained from the following Web site address: http://www.spk.usace.army.mil/​projects/​civil/​Lake_​Isabella_​Dam/​Index.html. Questions or comments regarding the Isabella Lake DSAP Project may be submitted through this Web site, or written questions or comments can be submitted by mail to Mr. Mitch Stewart, U.S. Army Corps of Engineers, Sacramento District, Attn: Planning Division (CESPK-PD-R), 1325 J Street, Sacramento, CA 95814. Requests to be placed on a mailing list may also be submitted through the Web site or to the address provided above.

FOR FURTHER INFORMATION CONTACT:

Mr. Mitch Stewart at [phone], e-mail [e-mail], or by mail to (see ADDRESSES).

SUPPLEMENTARY INFORMATION:

1. Background Information. Based on current engineering knowledge, the Corps has determined that the Isabella Lake main and auxiliary dams have a high risk of failure due to significant seismic, seepage, and hydrologic issues that exist. An external peer review panel, commissioned by the Corps, has recently confirmed that the Corps' Class I designation “Urgent and Compelling” is appropriate for the Isabella Lake dams for several reasons:

a. A possibility of piping along the outlet conduit of its auxiliary dam (piping may be defined as fissures or openings through which water can travel inside the dam);

b. Evidence that the auxiliary dam's drain blanket is not performing as intended;

c. Studies find that the Kern Canyon Fault, under the auxiliary dam's right abutment, is active;

d. Evidence that the upper 20 feet of the auxiliary dam's foundation is loose and might be subject to loss of shear strength during seismic loading;

e. Hydrologic studies indicate that the spillway is inadequate; and

f. Extremely high consequences of failure.

The panel recommended short-term risk reduction measures such as maintaining the current reservoir pool restriction elevation of 2,585.5 feet, 20 feet below normal pool. The panel also recommended long-term risk reduction measures including completion of on-going studies of major rehabilitation of the auxiliary dam and evaluation of the main dam's overall earthquake performance.

2. Remediation Alternatives. The draft EIS will address an array of remediation alternatives that are necessary to prevent loss of life, extensive downstream damage, functional loss of the project, and the loss of all project benefits. The exact nature and extent of the remediation alternatives will be determined based on the results of on-going geotechnical and engineering studies, public and agency input during the scoping period, and preparation of the draft EIS.

3. Issues To Be Addressed. The draft EIS will address environmental issues concerning the remediation alternatives proposed. Issues will be identified based on public input during the scoping process and during the preparation of the draft EIS. Issues initially identified as potentially significant include, but are not limited to: Soils and seismicity, hydrology and water quality, noise and vibration, air quality, socioeconomics, water supply, land use, recreation, visual and aesthetic resources, traffic and transportation, historical and cultural resources, vegetation and wildlife, special status species, and fisheries.

4. Public Involvement. Public scoping meetings will be held in May 2010 at specific locations to be announced within the local Isabella Lake DSAP Project area and in Bakersfield, California. The purpose of the public scoping meetings will be to present information to the public regarding the array of remediation alternatives proposed that may be addressed in the draft EIS, receive public comments, and solicit input regarding environmental issues of concern to the public. These meetings are intended to initiate the process to involve concerned individuals, and local, State, and Federal agencies. The public scoping meeting place, date, and time will be advertised in advance in local newspapers, and meeting announcement letters will be sent to interested parties. Written comments may also be submitted via Web site or mail to (see ADDRESSES).

5. Availability of the Draft EIS. The Corps intends to issue the draft EIS in May 2011. The Corps will announce availability of the draft EIS in the Federal Register and other media, and will provide the public, organizations, and agencies with an opportunity to submit comments to be addressed in the final EIS.

Dated: January 26, 2010.

Thomas Chapman,

Commander, Sacramento District, U.S. Army Corps of Engineers.