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Biscuit Flats Project

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Voltage – 230kV
Estimated completion date – 2022
Location – Phoenix, AZ

Project need
Relocate three to four miles of an existing 500/230 kilovolt (kV) transmission line, expand the planned Avery Substation, and add additional TS22 Substation to accommodate and serve a major planned advanced semiconductor manufacturing plant.

Project description
We are proposing to relocate approximately three to four of an existing 500/230kV transmission line approximately 0.5 miles to the north of the existing alignment to accommodate development of an advanced semiconductor manufacturing plant in Phoenix.

The developer of the manufacturing plant requested and is funding the relocation of the transmission line. The developer has stated that the manufacturing process is highly sensitive to overhead transmission lines. Additionally, the manufacturing plant uses an extensive amount of electric power and requires a robust 230kV system to serve its operations. To meet these needs, we will be expanding the size of a planned substation while constructing a new substation to maintain system reliability of the surrounding transmission system.

The proposed relocated transmission line and substation work is generally located 0.5 mile west of I-17, and approximately 0.5 mile south of the Carefree Highway in Phoenix. The entirety of the project is located on Arizona State Trust Land.

Public Hearing Information
The Arizona Power Plant and Transmission Line Siting Committee held hearings July 26-28 at the Briarwood Country Club in Sun City West, Arizona. At the conclusion of the hearings, the committee voted 10-0 approving the Recommended Order and Opinion to Amend Certificates of Environmental Compatibility (CECs 131 and 120. The Recommended Order and Opinion will next be heard at an upcoming Open Meeting of the Arizona Corporation Commission, which has yet to be scheduled.

Biscuit Flat 500/230kV Line Relocation Project Supplemental CEC Amendment Application 
Prefiling Exhibit 1 - Project Vicinity Prefiling Exhibit 2 - Public Hearing Sign
Prefiling Exhibit 3 - Road Sign
Prefiling Exhibit 4 - Social Media
Notice of Hearing
Prefiling Conference Information
Prehearing Meeting Transcripts
Evidentiary Hearing Transcripts – Document 1
Evidentiary Hearing Transcripts – Document 2
Evidentiary Hearing Transcripts – Document 3


Project Planning
In January 2021, we hired AECOM, an environmental consulting firm, to assist in evaluating the project site, to assess potential environmental impacts, and to support the public outreach process. Baseline information about land use, visual, biological, cultural and recreational resources for the area has been collected. Early in the project process, we began coordination with project area stakeholders including the Arizona State Land Department and the City of Phoenix in order to share project information and to collect input from them.

Project maps
Study Area
Existing Land Use
Future Land Use

Project features
We work hard to balance the energy needs of our customers while protecting the environment and natural beauty of the area.

The rebuilt transmission line structures will be similar in height and design of the existing structures. The steel monopoles are anticipated to be up to 150 feet in height*.

*Exact structure, height, and right-of-way width may vary.


Certificate of Environmental Compatibility (CEC) Amendments required
In order to relocate the existing transmission line and perform the substation improvements required for the development of the semiconductor plant, we need to secure the amendment of two CECs that currently govern the placement of the transmission line and the construction of the substations.

The two prior CECs that must be amended to permit development of the plant are CEC 120 and CEC 131. CEC 120 authorized us to construct a double-circuit 230kV transmission line between the Westwing, Raceway, and Pinnacle Peak substations and two new substations – the Scatter Wash and Avery Substations. While the Scatter Wash Substation was completed in May 2020, construction of the Avery Substation has not yet commenced. CEC 131 authorized us to construct a double-circuit transmission line with one 500kV circuit and one 230kV circuit and two substations – Morgan and Pinnacle Peak expansion. The construction of the Morgan-Pinnacle Peak 500kV Line and the Morgan-Raceway-Pinnacle Peak 230kV Line was completed and energized in December 2010. CEC 120 must be amended to permit us to expand the size of the Avery Substation site from what was authorized by CEC 120 to ensure adequate service to the plant. CEC 131 must be amended to permit us to relocate an approximate 3-4 mile segment of the existing Morgan-Pinnacle Peak Line from its approved corridor approximately 0.5 mile north to accommodate the operations of the plant and to authorize the construction of a third substation to ensure adequate service to the plant.

The amendment process for an existing CEC will require the project to be heard in a public hearing by the Arizona Power Plant and Transmission Line Siting Committee during the week of July 26-30. The specific dates and times have not been determined. Information regarding the public hearing will be advertised through multiple ways including here on this webpage. Please check back for more information regarding instructions for attendance.


Project Input
An important component of our siting process is the receipt of input from residents, tenants, property owners, businesses, and recreational users within the study area. Members of the public and all interested parties are invited to visit our virtual open house at any time online at biscuitflatsopenhouse.com, to learn more about the purpose and need for the project and the siting process. You will be able to provide input and, if desired, request a call to speak with one of our subject matter experts. If you cannot access the site online, you can call or email a request for a hard copy of the open house materials to be mailed.

We welcome your feedback for this project. All comments must be submitted by June 28, 2021, to ensure its review and consideration in this process. Comments and questions may be submitted within the virtual open house, by clicking the comments form link on this page, or by phone or email.


Public information virtual open house
Launch Date: June 14, 2021

Attend Online: biscuitflatsopenhouse.com

Comment Period: June 14, 2021 through June 28, 2021

Contact information

Kevin Duncan

Senior Siting Consultant

Project information phone number: 602-282-8890


Related documents
Newsletter #1

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