Tehachapi East Afterbay Project

CEQA Documents

The Tehachpi East Afterbay

The California Department of Water Resources (CDWR) proposes to construct a reservoir east of the bifurcation of the East Branch and West Branch of the California Aqueduct in southern Kern County; nine miles east of Gorman, California. The Tehachapi East Afterbay project (proposed project) would provide additional storage to the existing Tehachapi Afterbay (Pool 42). This additional storage would allow downstream facilities on the East Branch, and to a lesser extent, the West Branch, to operate for short periods without relying on the pumping operations of the Valley String Pumping Plants (Dos Amigos, Buena Vista, Teerink, Chrisman, and A.D. Edmonston), thereby reducing pumping during peak electrical demand periods and providing increased operational flexibility. Pumping could then be shifted from expensive, peak periods of power demand to off-peak periods when power rates are lower, resulting in cost savings and the statewide benefit of more efficient and stable energy consumption. The ability to shift to off-peak pumping is, however, often limited by a lack of regulatory storage and the need to maintain flow rates in the East Branch of the California Aqueduct.

Construction activities for the Tehachapi East Afterbay (East Afterbay) would occur over a 17-month period as estimated from the most recent project design information, and is tentatively scheduled for February 2005 to June 2006. The proposed project would consist of a reservoir (afterbay) with a water surface area that would cover approximately 71 acres, based on the normal maximum water surface elevation (of 3,100 feet), and have a gross storage capacity of approximately 1,159 acre-feet (AF). Virtually the entire reservoir pool would be constructed in excavation.

As a result of the proposed project, flow to the West Branch would remain relatively unchanged. Flow to the East Branch, which currently is routed through the existing Tehachapi Afterbay to Cottonwood Chutes or Alamo Powerplant, would diverge from the existing Tehachapi Afterbay into the East Afterbay via a new inlet channel designed to convey flows up to approximately 3,150 cubic feet per second (cfs). Water would then discharge from the East Afterbay into the Alamo headworks and/or Cottonwood Chutes (see Figure 2-3 in Section 2 – Project Description) via a new outlet channel. A new bypass around Alamo Powerplant and Cottonwood Chutes, which connects to Cottonwood Canal, would provide a third conveyance to the East Branch.

The CDWR has prepared a Draft Environmental Impact Report (DEIR) describing the project and its potential environmental effects. The DEIR specifically focuses on the proposed project's potential impacts to air quality and biological resources. Based on this document, it has been determined that the proposed project would have a significant unavoidable impact on air quality and biological resources during construction. A Statement of Overriding Considerations will be filed by the CDWR to proceed with the proposed project.

The Tehachapi East Afterbay Project Environmental Impact Report (EIR) may be found below (Adobe Acrobat Reader is needed) and consists of the Draft Environmental Impact Report dated September 2004 and the Final Environmental Impact Report dated December 2004.

Tehachapi East Afterbay Draft Environmental Impact Report

For further information, contact:

Mary Miller
E-mail: marym@water.ca.gov
Phone: 818 500-1645 x253

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Last modified: August 1, 2005
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