Rocky Mountain Power and Idaho Power Seek Certificates of Public Convenience and Necessity for Gateway West Segment E-8 Transmission Line
Summary
Rocky Mountain Power and Idaho Power have filed applications with the Idaho Public Utilities Commission seeking certificates of public convenience and necessity for Segment E-8 of the Gateway West project, a 500-kilovolt transmission line from the Midpoint Substation near Jerome, Idaho to the Hemingway Substation near Melba, Idaho. The segment is designed to provide 2,000 megawatts of additional transmission capacity and deliver energy to the Treasure Valley. Idaho Power will hold 99 percent ownership while PacifiCorp holds 1 percent. Construction is scheduled to begin in October 2027.
What changed
Rocky Mountain Power and Idaho Power submitted applications to the Idaho Public Utilities Commission for certificates of public convenience and necessity to construct Segment E-8 of the Gateway West project. This 500-kilovolt transmission line will span approximately 65 miles from the Midpoint Substation near Jerome to the Hemingway Substation near Melba, with an intermediate connection at the proposed Mayfield Substation.
Affected parties include the two utility companies seeking approvals, as well as property owners along the proposed route who may face eminent domain proceedings. The applications are now pending before the Idaho PUC for review and decision under Case Nos. IPC-E-26-09 and PAC-E-26-06.
Archived snapshot
Apr 21, 2026GovPing captured this document from the original source. If the source has since changed or been removed, this is the text as it existed at that time.
Case No. IPC-E-26-09 Case No. PAC-E-26-06 Order No. 37010 Contact: Adam Rush Office: (208) 334-0339 E-mail Address: adam.rush@puc.idaho.gov
NEWS RELEASE: Electric utilities file applications seeking certificates of public convenience and necessity to begin construction of transmission line segment.
BOISE (April 20, 2026) - Rocky Mountain Power and Idaho Power have filed applications with the Idaho Public Utilities Commission seeking certificates of public convenience and necessity that would allow the utilities to begin construction of a proposed transmission line segment that is designed to provide an additional 2,000 megawatts in transmission capacity.
Segment E-8 of the Gateway West project is a 500-kilovolt line that will start at the Midpoint Substation near Jerome, Idaho, and run to the Hemingway Substation near Melba, Idaho. Segment E-8 also will connect to Idaho Power's proposed 500-kilovolt Mayfield Substation.
The utilities stated that Segment E-8 will add transmission capacity and deliver energy to the Treasure Valley from Mountain Home and the Magic Valley in the Twin Falls area. Construction on Segment E-8 is scheduled to begin in October of 2027 and will be completed in three phases. Phase I and II will connect the Hemingway Substation to the Mayfield Substation while phase III will extend the Mayfield Substation to the Midpoint Substation. Phase III is expected to begin in
2030.
Idaho Power will hold 99 percent ownership in the segment and Rocky Mountain Power's parent company, PacifiCorp, will hold the remaining 1 percent.
Additional information is available at: puc.idaho.gov/case/Details/7741 and puc.idaho.gov/case/Details/7740.
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