Biscuit Flats Project

Mother cooking with young boy


Voltage – 230kV
Estimated completion date – July 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 relocating approximately three to four miles 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 was heard at the September 8-9 Open Meeting of the Arizona Corporation Commission, where it received unanimous approval.

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
Decsion #78251

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 have secured 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 were 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 was 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 was 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.

Although the public siting process is now complete, open house material and information can still be viewed online at
biscuitflatsopenhouse.com. Comments or questions can be submitted to: 

Lupe Martinez

Siting Consultant

Related documents
Newsletter #1
Decision #78251


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