SMUD cancels 500-kV transmission line project

SMUD is canceling the proposed Colusa-Sutter Transmission Line Project (CoSu) effective immediately. 

During CoSu’s initial phase—which was to evaluate potentially significant environmental impacts and conduct permitting and preliminary engineering to decide whether to proceed with final design and construction—it was determined that the project is too costly. The initial estimated $245 million cost of CoSu has increased by more than $100 million and could have ended up being higher.

Additional cost increases were also expected to address flood risk at the O’Banion Substation study area, an issue uncovered during the environmental review process. The decision to exit the project now comes early enough that SMUD will save approximately $4 million in this planning phase.

SMUD and the Western Area Power Administration (WAPA) have been working on CoSu since the SMUD Board of Directors approved the Project Development Agreement in December 2014. The proposed 500-kilovolt transmission line would have connected the California–Oregon Transmission Project to SMUD’s or WAPA’s transmission facilities on the west side of the Sacramento Valley.

Since SMUD started planning the project, the development of SMUD’s long-term Integrated Resource Plan (IRP) has greatly reduced the value and need of the proposed line. The IRP analysis indicates SMUD would better focus its resources on the suite of local, regional and in-state renewable and reliability projects, as well as incremental transmission infrastructure.  Canceling CoSu also reduces pressure on SMUD rates during the early critical phase of IRP implementation.  

Additionally, joining the California Independent System Operator (CAISO) Energy Imbalance Market, in which SMUD will start participating in April 2019, will provide lower cost access to a broader regional market.

Since the SMUD Board made the initial approval, SMUD and WAPA staffs focused on developing a robust environmental review process, with numerous public meetings throughout four counties and studies to help ensure an appropriate mitigation strategy to minimize or avoid impacts on various resources.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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