The Colusa-Sutter Transmission Line, or CoSu Line Project, was a proposed 500-kilovolt (kV) transmission line project that was recently being studied by the Western Area Power Administration (WAPA) and Sacramento Municipal Utility District (SMUD). The CoSu Line Project would have provided a new link between the California-Oregon Transmission Project (COTP) and SMUD and WAPA’s facilities on the east side of the Sacramento Valley. The proposed project was expected to enhance the reliability of the electrical grid in Northern California and increase SMUD’s ability to import power from the Pacific Northwest and export power from the Sacramento area.

This new link between the COTP and the Sacramento Valley was proposed as:

  • improve local and regional energy reliability;
  • help the region meet required reductions in greenhouse gas emissions
  • help the region meet required renewable energy content goals
  • ensure the continued safe and reliable operation of the regional transmission system to deliver clean power to homes and businesses in the region;
  • assist SMUD in planning for anticipated growth and energy demand; and​
  • improve the transmission infrastructure network and the Sacramento area’s import/export capabilities


Project Update – March 1, 2019

The proposed Colusa-Sutter (CoSu) 500-kilovolt transmission line project is canceled effective immediately. Accordingly, the release of the Draft Environmental Impact Statement/ Environmental Impact Report, planned for public release in mid-2019, is also canceled.

Since 2015, the Sacramento Municipal District (SMUD) and the Western Area Power Administration (WAPA) have been working on CoSu, evaluating potentially significant environmental impacts to decide whether to proceed with final design and construction.  The proposed 500-kilovolt transmission line would have connected the California–Oregon Transmission Project (COTP) to SMUD’s or WAPA’s transmission facilities on the west side of the Sacramento Valley.

During the project planning phase, the cost estimate increased, and the value and the need of the proposed line diminished for SMUD; therefore, SMUD made the decision to cancel the project and focus its resources on the suite of local, regional and in-state renewable and reliability projects, as well as incremental transmission infrastructure


If you need information regarding the proposed CoSu Line Project, you can make contact though the following methods:


Mr. Andrew M. Montaño
National Environmental Policy Act (NEPA) Document Manager
Western Area Power Administration, Headquarters
P.O. Box 281213
Lakewood, Colorado 80228-8213​




Last modified on August 3rd, 2023