Granite Wins $50M Job to Replace PG&E Dam Spillway After Oroville-Driven Review
Granite Construction has been awarded a $50-million contract to replace the spillway at PG&E’s Tiger Creek Regulator Dam in Northern California, Engineering News-Record reports, after safety reviews triggered by the 2017 Oroville Dam failure found the existing system inadequate.
Market Impact
According to ENR, the contract follows spillway assessments PG&E conducted after federal and California dam-safety regulators required hydroelectric operators to reevaluate aging spillways using updated hydrologic modeling. At Tiger Creek, engineers found deterioration in the existing spillway chute, uncertainty over whether the dam’s three spillway siphons would activate as intended, and hydraulic capacity well short of what’s needed under probable maximum flood conditions.
The numbers tell the story: the existing spillway could safely pass about 2,750 cubic feet per second, less than half the site’s estimated 5,653-cfs probable maximum flood, per ENR. Because the 1931 dam wasn’t designed to withstand overtopping, PG&E chose a replacement spillway rated to pass up to 6,000 cfs rather than attempt a rehabilitation. Construction began in May and is scheduled for completion in May 2028. Granite previously completed a roughly $600,000 preconstruction contract covering constructability reviews and early planning, ENR reported.
What It Means for Subcontractors
- Earthwork and concrete crews should note the scale: ENR reports the job requires about 35,000 cu yd of excavation and roughly 4,000 cu yd of structural concrete, plus rock anchoring, a temporary cofferdam, and a new permanent access road, work packages likely to draw specialty subs through 2028.
- Firms with cofferdam and dewatering experience have a clear opening here: construction will happen behind a temporary cofferdam during a planned reservoir drawdown, letting crews build in dry conditions while the reservoir keeps operating.
- Excavation haulers and site logistics contractors should track the Doakes Ridge staging and spoils site named in state-certified project documents as the destination for excavated material during the project.
- Hydroelectric operators statewide are running the same post-Oroville hydrologic reevaluations that flagged Tiger Creek’s deficiencies, so engineering firms and contractors with spillway modeling, chute construction, and abutment excavation experience should expect similar replacement contracts to surface at other aging California dams.
- General contractors bidding future dam-safety work can point to the Tiger Creek model, a new spillway built along the right abutment with a 40-ft-wide chute, flip bucket, and plunge pool, as a template PG&E and regulators have already accepted over rehabilitating the original structure.
