Proving Ground Solar and Storage 500kV Interconnect

Father holding toddler outside


Voltage: 500kV
Estimated Siting completion date: 1st quarter 2023
Location: North of Dateland, AZ

Project need
A new 500 kilovolt (500kV) transmission line is required to interconnect a portion of the Proving Ground Solar and Storage Project north of Dateland, from a new step-up substation to the Hoodoo Wash Substation.

Project description
The project involves a 250-megawatt (250MW) solar photovoltaic generating facility with battery storage, an approximately 6-mile-long double circuit 69-kilovolt (69kV) generation intertie transmission line (gen-tie), a step-up substation, and a 500-kilovolt (500kV) interconnection transmission line (interconnection line) from the step-up substation to the Hoodoo Wash Switchyard. The interconnection line will be an approximately 3,000-foot-long, 500kV transmission line. The solar + storage facility will be located on approximately 2,050 acres of privately owned land, the gen-tie will be located on right-of-way (ROW) from the Arizona State Land Department and Bureau of Land Management (BLM), and the step-up substation and interconnection line will be on ROW from the BLM and across privately owned land. The project and interconnection facilities will be located north of Palomas Road, approximately 10 miles north of Dateland, in unincorporated Yuma County.

Project Map 1
Project Map 2

Project Planning
In 2018, the Yuma County Board of Supervisors approved a special use permit to allow construction and operation of the project in conformance with the Yuma County Zoning Ordinance. A portion of the gen-tie, the step-up substation, and a portion of the interconnection line will be located on rights-of-way obtained from the Arizona State Land Department, across Arizona State Trust land, and from the Bureau of Land Management (BLM). We are currently working with the BLM to amend its existing right-of-way grant to match the final design of the 500kV interconnection line, step-up substation, and associated improvements on BLM-managed lands.

In November 2021 newsletters were mailed to the public to announce the project and requested attendance of an open house meeting at the Dateland Elementary School in December 2021 to present information about the project, answer questions, and receive comments.

Additional newsletters, newspaper ads, social media posts, and project webpages were used to provide project updates, information regarding the Certificate of Environmental Compatibility (CEC), the CEC hearing, and how to participate in the process. 

Project features
We are coordinating the design of the interconnection line with Strata Clean Energy, LLC (Strata) and have carefully considered the potential visual impacts in siting the proposed step-up substation and interconnection line. The 500kV portion of the new line would be co-located on existing 500kV structures. Co-locating this portion of the interconnection line will help consolidate energy infrastructure and minimize visual impacts overall. The visual simulations showing existing and proposed conditions from two perspectives on Palomas Road are depicted below.

Simulation #1
Simulation #2

We anticipate that the CEC process will be complete in early 2023, subject to the availability of the Arizona Power Plant and Line Siting Committee. Construction for the project is estimated to begin in Spring 2023.

Project updates
On Jan. 5, 2023, we filed an application for a Certificate of Environmental Compatibility (CEC) with the Arizona Corporation Commission (ACC); the Interconnection Project is docketed as L00000D-23-0011-00214. This project will be presented at a hearing before the Arizona Power Plant and Line Siting Committee (Siting Committee). If approved by the Siting Committee, the CEC will then be presented to the ACC for their consideration and final decision.

Public Hearing Information
December 20, 2022: A CEC Prefiling Conference was held with the Chairman of the Arizona Power Plant and Transmission Line Siting Committee to discuss the application, public hearing agenda, and ensure proper notifications and filing requirements will be met. PDF copies of the prefiling conference transcripts, prefiling exhibits, and notice of hearing can be viewed within the Evidentiary Hearing documents below.

January 5, 2023: An application for a Certificate of Environmental Compatibility (CEC) was filed at the ACC Docket Control. The docket number for this Project is L-00000D-23-0011-00214. A PDF copy of this CEC (CEC-214) application can be viewed within the Evidentiary Hearing documents below.

February 7, 2023: A Prehearing conference was held with the Chairman of the Arizona Power Plant and Transmission Line Siting Committee to ensure notification requirements were met and discuss evidentiary hearing protocol and expectations. A PDF copy of the prehearing conference transcripts can be viewed within the Evidentiary Hearing documents below.

February 13-14, 2023: The Arizona Power Plant and Transmission Line Siting Committee (Committee) held hearings on this project beginning at 1 PM on February 13th at the Yuma Four Points by Sheraton Hotel and Conference Center - 2030 S. Avenue 3E, Yuma, AZ 85365. A Public Comment Period was also held that same day at 5:30 pm. Notification was sent to the public before the hearings to provide information for attendance in person or on-line. The Committee completed the evidentiary hearings on February 14th 2023, and voted unanimously to grant the CEC for their Preferred Route.

February 17, 2023: The Committee Chairman submitted CEC-214 to the Arizona Corporation Commission (ACC) for their consideration. The ACC can either grant the CEC as proposed, modify, or deny the CEC at an open meeting, expected  in April 2023.

April 17, 2023: The case for CEC-214 was presented during the ACC Open Meeting and received a unanimous vote of approval.

Next Steps
With the completion of the siting efforts, and the acquisition of the CEC, the construction phase of this project is expected to begin in 2024. This includes engineering and design, acquiring the easements and rights-of-way, and finally the construction of the line.

Public input
Although the public siting process is now complete, comments or questions can be submitted by email to:

Siting Consultant


Related documents
Newsletter #1
Newsletter #2
Newsletter #3
Newsletter #4
Project Overview Boards
Prefiling Exhibits
Prefiling Transcripts
CEC-214 Application
Notice of Hearing
Hearing Agenda
Procedural Order
Prehearing Exhibits
Prehearing Transcripts
Hearing Transcripts Day 1
Hearing Transcripts Day 2
Notice of Filing CEC-214


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