The California Independent System Operator (CAISO), the regional electric grid operator, selected Horizon West Transmission to build and operate an approximately 86-mile, 500-kilovolt electric transmission line to improve the reliability of the local electric grid and provide access to low-cost energy. The project will also spur job opportunities and investment in the community while generating additional opportunities for economic development.

The Ironwood Transmission Line would connect existing electric transmission infrastructure in Yuma County, AZ, with existing infrastructure in Imperial County, CA.

In September 2025, Horizon West submitted a Proponent’s Environmental Assessment (PEA) and application for a Certificate of Public Convenience and Necessity to the California Public Utilities Commission (CPUC) to request authorization to construct the Ironwood Transmission Line for the California portion of the line. Our submission includes a proposed route shaped by feedback from local landowners, communities, tribes, government agencies and other stakeholders. As the line is proposed to cross both California and Arizona, in early 2026, we will be submitting an application to the Arizona Corporation Commission (ACC) for the Arizona portion of the line.

To build the transmission lines in Arizona, Horizon West Transmission must obtain a Certificate of Environmental Compatibility (CEC) from the ACC. The ACC issues a permit based on several criteria, including project need, cost and environmental impact. The process provides opportunities for public participation and is as follows:

• Horizon West conducts environmental studies and solicits public input to identify a proposed and alternative routes

• Horizon West submits a CEC application with the proposed route

• ACC’s Power Plant and Transmission Line Siting Committee holds public hearings and reviews the application

• Siting Committee recommends the ACC approve, modify or deny the CEC

• ACC reviews Siting Committee’s recommendation during a public meeting

• ACC votes to approve, modify or deny the CEC

• If approved, the CEC is issued within 180 days of application submission