Relicensing the South Fork Tolt Hydroelectric Project
Project Description
The City of Seattle owns and operates the South Fork Tolt Hydroelectric Project (Project) under a license administered by the Federal Energy Regulatory Commission (FERC). Through Seattle City Light and Seattle Public Utilities, the City is working to relicense the Project and will be working closely with federal and state agencies, Tribes, and other licensing participants throughout the multi-year relicensing process.
The 16.8-megawatt Project is City Light’s newest hydroelectric facility. The Project was completed in 1995 to generate electricity from the existing Tolt Reservoir and Dam, which are owned and operated by Seattle Public Utilities to provide about 30-40% of the drinking water supply for 1.6 million people in the greater Seattle area.
The City's goal for the relicensing process is to obtain a new FERC license that enables City Light to continue to deliver affordable, reliable, and environmentally responsible energy services to our customers in a manner that maintains the City's long-term water supply. While the Project supplies less than 1% of City Light's power requirements, it is an important source of renewable energy for its customers. It powers the Tolt Water Treatment Facility and helps balance out the power provided by other renewable sources in the region, thus filling in gaps and increasing resiliency within the local power grid.
FERC issued the City its original license for the Project in the 1980s. This 40-year license will expire in July 2029. The City formally initiated the relicensing process with the filing of its Notice of Intent (NOI) to relicense the Project, as well as a Pre-Application Document (PAD), on April 8, 2024. The City will continue to work with Tribes, federal and state resource agencies, Licensing Participants, and other interested parties to develop and implement a study plan, which will inform the City’s application for a new license to be filed with FERC no later than July 19, 2027.
Location
The Project is located on the South Fork Tolt River, approximately 35 miles east of the city of Seattle in the foothills of the Cascade Mountains, near the towns of Carnation and Duvall. All Project facilities are located within unincorporated King County on the South Fork of the Tolt River, which merges with the North Fork Tolt River below the Project to form the Tolt River, a tributary to the Snoqualmie River.
Community Benefits
Issuance of a new FERC license will allow the City to continue producing clean, carbon-free energy from the Project for the next 30-50 years. Through the relicensing process, the City will coordinate with licensing participants and interested parties to develop proposed protection, mitigation, and enhancement measures for inclusion in the new license to benefit environmental and cultural resources impacted by the Project during the new license term.
What's Happening Now?
Project Update (March 2025): The Federal Energy Regulatory Commission (FERC) issued their formal Study Plan Determination on Feb. 13, 2025. The document is their guidance in response to the City’s proposed and revised study plans. This is a significant milestone, moving us into the next phase of work to relicense the South Fork Tolt Hydroelectric Project.
You can access FERC’s Study Plan Determination and other documents related to the relicensing process by visiting the Public Documents Library. You can find this in the “Project Documents and Resources” section below.
The City will continue to work with Tribes and other Licensing Participants during the study implementation phase to help us better understand the South Fork Tolt. The list of studies that will be completed in the coming years includes those required by the Study Plan Determination as well as additional research agreed between the City and Licensing Participants.
Visit the online library to find relicensing documents for the South Fork Tolt Project, background information about the South Fork Tolt Municipal Watershed, and additional resources as they become available.
High-Tech “Spherical” Video of the South Fork Tolt Project
This interactive spherical video provides an opportunity to view the hydroelectric project and its facilities, the Tolt Reservoir and Dam, and the South Fork Tolt River as it joins the Tolt River and enters the Snoqualmie River.