DWR enters first phase of hoist replacements at Oroville Dam

Jul 13, 2023

OROVILLE — The California Department of Water Resources has begun its nine-year project to replace the spillway gate hoists at the Oroville Dam.

Workers began the process of reverse-engineering the hoists Tuesday to open the door for replacing one per year in a project expected to be complete in 2031.

Scott Turnquist, DWR’s engineering branch manager for the Oroville field division, said the project is the result of years worth of planning in an effort to have large-scale maintenance on the dam. The construction window for reverse-engineering and eventually replacing the hoists can happen between May and October when Lake Oroville is typically at a lower water level.

The project is expected to cost $5 million.

Over the course of the project, hoists will be created and put in seasonally. DWR has enlisted outside company Unico to help in the building and replacement process.

“This winter, this coming flood season, they will fabricate the first gate hoist assembly replacement unit,” Turnquist said. “And then next year during the dry season, in the summertime when it’s safe to take the gates out of operation, and then Unico will swap out the old one and put on the new one.”

There are eight gates at the main Oroville Dam spillway, often referred to as the Flood Control Outlet, or FCO, and each is controlled by a hoist that can pull the gates up to release water. Turnquist said this can happen as a way to avoid flooding. For example, the Army Corps of Engineers put requirements in place that the lake can only rise to a certain level to account for large storms and snow melt. If the lake goes above that level, gates must be opened and the water relieved.

Turnquist said construction will involve concrete grading as well as mechanical work on the hoists above the spillway throughout the summers as the project goes forward.

“This is just routine, ongoing maintenance,” Turnquist said. “It’s something that a normal dam owner is going to be doing. A hoist assembly are something that wears out and you replace over time, and there’s a lot of maintenance that goes on outside of replacement and now we’re to the stage where we’re ready to do a larger scale refurbishment.”

Maintenance and replacements come into play based on a series of reviews done by outside agencies such as the Federal Energy Regulatory Commission as well as DWR’s internal dam safety branch. The spillway gates themselves, Turnquist said, were not considered damaged and therefore don’t require replacements yet, however, the hoists, based on yearly usage, were pointed out as a spot in need of assistance.

Turnquist said the review and background work occurs to maintain dam safety.

“So in all of that work is an effort to ensure that when we need to operate the gates, they operate,” Turnquist said. “They’ll go up and down. So the biggest components are paramount for the operations of the FCO.”

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