Western Area Power Administration (WAPA) is preparing an Environmental Assessment (EA)* to evaluate the environmental effects of the Arizona Peaking Capacity Energy Storage Project (Project) in which the AES Energy Storage, LLC, has submitted a project proposal to WAPA for potential financing under the Transmission Infrastructure Program for the proposed Project. WAPA could provide project financing from the United States Treasury under authority granted to WAPA under Section 402 of the American Recovery and Reinvestment Act of 2009 (Recovery Act) (Public Law 111-5), which amended the Hoover Power Plant Act of 1984 (Public Law 98-381). The proposed Project would involve the construction of a 100-megawatt (MW) battery energy storage facility adjacent to the existing Arizona Public Service (APS) Westwing Substation within Maricopa County, Arizona. As a cooperating agency, the U.S. Bureau of Reclamation (Reclamation) would be responsible for approval of the proposed Project’s Large Generator Interconnection Agreement (LGIA) request which would allow interconnection to the APS Westwing Substation​.

*DISCLAIMER: WAPA’s preparation of the EA or performance of any other environmental analysis related to this Project is not a final decision or determination as to whether WAPA will provide project financing for this Project.


The proposed Project would construct a 100-MW battery storage facility in Maricopa County, Arizona. The proposed battery storage facility would utilize advanced technology batteries and control systems contained within an approximately 523-foot by 295-foot (154,300 sf or 3.5-acre) area screened by a solid 8-foot tall perimeter wall. The proposed battery storage facility would consist of battery storage containers, inverters/transformers, communications equipment, switchgear, and heating, ventilation, and air conditioning (HVAC) units. In addition, transmission poles and associated electricity transmission facilities would connect the project site to the APS Westwing Substation to the south.


September 2021: WAPA has completed its environmental review process of the proposed Project and the​ Final Environmental Assessment and the Finding of No Significant Impacts (FONSI) have been issued and can be found in the DOCUMENTS section below. ​​The next steps would be for WAPA to potentially provide Project financing under the Transmission Infrastructure Program. The completed environmental review helps inform WAPA’s consideration of any loan application under its borrowing authority from the U.S. Treasury. Since Reclamation was a cooperating agency in this environnental review, Reclamation plans to respond to AES’s application for interconnection by approving and signing a Large Generator Interconnection Agreement (LGIA) with AES. The approval of the LGIA by Reclamation and other participants would allow AES to interconnect to the Arizona Public Service (APS) Westwing Substation.

If you need further assistance related to WAPA’s environmental review, please contact Andrew Montaño via the CONTACT section below.


For more information on this proposed Project, please contact:

Mail: Western Area Power Administration, HQ
ATTN: Andrew M. Montaño, NEPA Document Manager
P.O. Box 281213
Lakewood, CO 80228-8213
Phone: (720) 962-7253


Last modified on June 26th, 2023