Three Peaks to Purgatory Flat

Project overview

PacifiCorp plans to build a new 60-mile 345 kilovolt single-circuit transmission line between the existing Three Peaks substation near Cedar City, Utah, to the existing Purgatory Flat substation near Washington, Utah. The new transmission line will provide additional capacity to help serve growing customer needs in Utah while increasing overall system reliability.  This line will deliver electricity generated from PacifiCorp’s generating resources, including renewables and thermal resources, while adding the benefits of increased reliability and capacity. 

About the project 

The purpose and need for the Three Peaks to Purgatory 345 kV line is to ensure the transmission system is reliable. The significant growth that Southern Utah has experienced has increased the demand for energy, and that demand continues to rise. There has also been an increase in solar power development in southern Utah and this new line is needed to economically meet reliability requirements and transport resources across the service area. Without a new line, if an outage is experienced, the area’s transmission system would not meet reliability planning standards. The line will strengthen resiliency and optimize the capability of the transmission network to support renewable and other energy resources.  

  • Voltage: 345 kV
  • Type of Structure: steel transmission tower, H-frames and Single poles
  • End Points: Three Peaks substation (Cedar City) and Purgatory Flat substation (Washington)
  • Length: Approximately 60 miles
  • Right of Way: 150-230 feet
  • Anticipated in-service date: August 2032

Project map

The project is in the planning stages. PacifiCorp is conducting a routing study and meeting with local agencies to gather information in efforts to identify a suitable route. Route selection takes into consideration impact on existing land uses, biological and environmental factors, known resource constraints and feasibility. Considering these factors, certain route options have been eliminated from further consideration.

Three Peaks to Purgatory Flat Project Map

Project benefits

Reliability 

  • Improve energy delivery capacity for the southern Washington County area in both normal system conditions, and in cases where outage may affect other transmission paths. 
  • Increase transmission capacity in Washington County.
  • Reduce likelihood of service interruptions due to safety.

Economic development

  • Provide for the increasing electrical usage as southern Washington County continues to experience growth. 

Increased resilience from extreme event or wildfire

  • A new 345 kV line with boost system resiliency in the St. George area. All existing major transmission lines serving the area are in a common corridor and could be impacted simultaneously by an extreme weather event or wildfire.
  • Reduced probability of a Public Safety Power Shutoff due to wildfire conditions.

Project timeline

Public outreach 2025-2026
Permitting 2027-2029
Engineering 2027-2029
Rights-of-Way 2028-2030
Construction 2030-2032
In-service August 2032