Project Description
The Southwest Tucson Reliability Project will create a looped transmission system to provide greater reliability, power quality, and capacity to southwest Tucson. New transmission facilities will replace older, lower-voltage equipment that cannot keep pace with customers’ growing energy needs.
The project will include building two new 138 kilovolt (kV) circuits and a new 138-kV substation.
The first phase will involve building a new transmission line from TEP’s existing Midvale Substation, located near South Mission and West Drexel roads, to the planned Tucson Estates Substation, located near West Ajo Highway and South Tucson Estates Parkway. The substations are located about 5 miles apart.
The second phase will build a new transmission line from Tucson Estates Substation to tie into an existing 138kV transmission line located near West Valencia Road and Calle Santa Cruz. These two interconnection points are about 8 miles apart.
The planned Tucson Estates Substation will encompass about 15 acres on the southeast corner of West Ajo Highway and South Tucson Estates Parkway.
The project will help reduce the duration and frequency of power outages in the area, while also supporting options for maintenance and emergency repairs.
Typical transmission poles will stand about 75-85 feet tall and about 600-1,000 feet apart. Some poles may be taller to accommodate site-specific clearance issues. Lines will be designed to accommodate two circuits using tubular, self-weathering steel monopoles with non-reflective surfaces. Conductors (wires) will have a non-specular finish to reduce visibility.
Public Open House
Thursday, March 5, 2026 | 6-8 p.m.
Light refreshments will be provided.
Raúl M. Grijalva Elementary School
1795 W. Drexel Rd.
Tucson, AZ 85746
Project Benefits
Project Map
Required Approvals and Timeline
Under state law, TEP must secure a Certificate of Environmental Compatibility (CEC) to build the transmission lines. TEP plans to file a CEC application in late 2026 with the Arizona Power Plant and Transmission Line Siting Committee, which reviews CEC applications in a public process that allows neighbors and others to provide comments. The Arizona Corporation Commission (ACC) must review and approve the CEC before TEP can begin construction.
Construction of the first phase is expected to begin in 2028, with an in-service date in 2029. The second phase is expected to be constructed and in-service by 2030.
October 2025–September 2026
Transmission Line Siting Process
September 2026
CEC Application Filing
November 2026
Line Siting Hearing
Q1 2027
ACC Open Meeting
Outreach Materials
March 2026
Public Participation
TEP encourages residents, property owners and others to participate in the line siting process. Please submit your comments and questions by:
- Attending public open houses
- Filling out an online comment below
- Sending email comments to swtucson@tep.com
- Calling 1-520-770-7522 and leaving a voicemail message
- TEP SW Tucson Reliability Project
P.O. Box 711
Mail Stop CB200
Tucson, AZ 85701-0711