09 Nov Folsom Dam Raise Project Reaches Major Milestone With First Full Opening of Retrofitted Spillway Gate
The successful operation of a 150-ton gate marks an important step in strengthening flood protection for the greater Sacramento region.
Folsom Dam Constructors, a joint venture between CEC and Shimmick, has reached a significant milestone on the Folsom Dam Raise Project in California. Following more than a year of extensive structural and mechanical upgrades, Gate 8 successfully completed its first full opening, marking the beginning of commissioning and a major step toward returning the gate to service.
The project, being delivered for the U.S. Army Corps of Engineers, involves retrofitting eight existing spillway gates to improve the dam’s flood management capabilities. These improvements are designed to allow Folsom Lake to temporarily accommodate an additional 3.5 feet of water during major storm events, providing greater flexibility to manage reservoir levels and release water downstream in a controlled manner. This additional floodwater storage capacity will help reduce flood risks for Sacramento and surrounding communities.
A Critical First Step
Gate 8 is the first of the eight gates undergoing retrofit and serves as the project’s proof of concept, allowing the team to demonstrate the engineering design and construction processes before advancing the remaining gates.
Measuring 42 feet wide and weighing approximately 150 tons, the gate has undergone extensive modifications since work began in March 2025. The retrofit includes replacement of structural steel members, gate trunnions, and the mechanical hoisting systems responsible for lifting the massive structure. Throughout construction, the gate was taken completely out of service and temporarily supported to accommodate the work.
The recent successful operation marked the first time the reconstructed gate traveled through its full operating range, rotating upward through 42 vertical feet of lift. This achievement represents a significant step in the commissioning process and brings the team closer to returning Gate 8 to full service.
Collaborative Engineering and Problem-Solving
Retrofitting critical infrastructure within an existing dam presents complex engineering challenges, particularly when construction must accommodate stringent design requirements. Throughout the Gate 8 retrofit, the project team has worked closely with the U.S. Army Corps of Engineers to evaluate technical issues, develop solutions, and coordinate their implementation.
A key part of this effort has been a weekly technical task force bringing together engineering representatives from Folsom Dam Constructors and the Army Corps. These collaborative meetings have provided a dedicated forum for addressing engineering challenges and advancing the work through the various stages of construction.
The successful full opening reflects the extensive planning, technical expertise, and coordination required to retrofit a structure of this size and complexity. With Gate 8 now entering commissioning, the project team is moving toward returning the gate to service and applying lessons learned from the proof-of-concept work to the remaining seven gates.
As the Folsom Dam Raise Project progresses, these improvements will contribute to the dam’s long-term flood management capabilities, helping strengthen critical infrastructure and protect communities throughout the greater Sacramento region.