Merrill to Coolidge 69kV Transmission Line Project

Family on the couch using a tablet


Voltage – 69kV
Estimated completion date – Q1 2027
Location – Arizona, Pinal County, Coolidge – Florence area 

Project Need

The project is needed to meet the expanding energy needs of more people and businesses throughout APS territory in the Pinal County area.  

This project will connect the Merrill and Coolidge substations to create a looped system, improving reliability in the region.

Project Description and Features

The project involves constructing, operating and maintaining a 69 kilovolt (kV) transmission line between the existing Merrill and Coolidge substations. The line will be approximately 8.5 miles long.

Below is an example of the type of structure we are proposing. The proposed line will be constructed as a double-circuit configuration on steel monopoles with a 12kV line built underneath on the same structure, referred to as underbuild. They will be approximately 65 feet in height depending on terrain and engineering requirements like crossing roads and other power lines. The transmission line will require a right of way or easement approximately 30 feet on each side of the line to safely construct, operate and maintain the line.

Typical pole structure for 69kV

Project Planning

In early 2023, we started a siting study to identify and evaluate alternative routes for the proposed transmission line, assess potential environmental impacts and support the public outreach process.

When developing alternative routes, we evaluated criteria like environmental impacts, engineering and construction feasibility, land acquisition timing and costs, regulatory approvals, potential impacts on existing and planned neighborhoods and input from agencies and the community.

Route Selected

After evaluating the route alternatives and considering input from the public, a route was selected to move forward with permitting. The selected route crosses the least number of properties, is located near the fewest homes and minimizes effects on environmental resources when compared to the other routes. The proposed route connects the Merrill Substation (south side of Merrill Ranch Pkwy. and east of North Felix Rd. in Florence) and the Coolidge Substation (north of Hwy. 87 and west of Arizona Blvd. in Coolidge) by following Hunt Highway, North Christenson Rd., and North Arizona Blvd.

With the completion of the siting efforts, we will begin the permitting process this year. Construction of this project is expected to begin in fall 2026. The construction phase includes engineering and design, acquiring easements and rights of way, and construction of the transmission line.

Preferred route for the Merrill-Coolidge line

Public Input

An important component of this siting process was gathering input from the public in the project siting area. We established a project-dedicated phone line and email, sent newsletters to provide updates and encouraged participation in public open house meetings. On September 14, 2023, we hosted a public open house to introduce the project and encourage public input on the project and several route alternatives. The input we received contributed to our siting study and resulted in the identification of three preliminary alternative routes. On December 7, 2023, we hosted a public open house to update the public on the status of the siting study and encouraged input on the route alternatives. Further evaluation and public input resulted in the selected route.

Anticipated Project Schedule

Project Planning 2023-2024 | Permitting 2024 | Construction Q4 2026 | In Service Q1 2027


Open Houses Newsletters Project Maps Fact Sheet
FAQ Page
Comment Form (Opens in new window)  
For more information: Project information phone line: 1-602-812-5829 or toll free at 1-888-687-2144
Project email: MerrilltoCoolidge@aps.com
  Lupe Martinez, Siting Consultant
Arizona Public Service
2121 West Cheryl Drive
Mail Station 3293
Phoenix, AZ 85021
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