Yuba Water Agency has awarded a $13.9m contract to Hat Creek Construction & Materials for hillslope and soil stabilisation around the penstock and New Colgate Powerhouse in Yuba County, California. The work forms part of the agency’s ongoing recovery programme following the major rupture of the New Colgate penstock on 13 February 2026.
Under the contract, Hat Creek will place slope and soil stabilisation materials, construct a rock buttress on the east side of the penstock to reduce the risk of further hillside damage, and build detention basins to manage rainfall runoff. Construction is scheduled to begin in September and will continue for as long as weather conditions permit.
“This project is an important step in stabilising the soil and slopes around our penstock and protecting our facilities and the river from additional sediment and runoff ahead of the rainy season,” said Yuba Water Senior Engineer Matt Murray.
The stabilisation work is one element of a wider, multi-year programme to restore the New Colgate facilities following the February incident.
The 14ft-diameter penstock ruptured shortly before 3pm on 13 February above New Colgate Powerhouse on the North Yuba River at Dobbins. Yuba Water estimates that approximately 400 acre-feet of water was released from the tunnel and penstock system, flowing down the hillside towards the powerhouse.
The incident caused extensive erosion and significant damage to New Colgate Powerhouse, two switchyards shared with Pacific Gas & Electric and sections of Lake Francis Road. Transmission and power lines were also damaged, while sediment and debris were carried into the Yuba River above Englebright Dam.
Around 60,000 cubic yards of sediment were deposited in the Yuba River below the powerhouse, according to Yuba Water. Sediment removal began in May as part of work to restore the river channel and support the eventual return of the powerhouse to operation.
New Colgate Powerhouse and the penstock remain out of service, with Yuba Water warning that electricity generation at the facility could be suspended for several years while restoration work is completed.
Recovery work has also included repairs to Lake Francis Road, removal of mud and debris from New Colgate Powerhouse and assessment and restoration of electrical and other systems inside the facility. Yuba Water said sediment on the powerhouse deck was more than 13ft deep in places, amounting to approximately 11,000 cubic yards.
The agency is meanwhile working with forensic engineers to establish the cause of the rupture. The investigation remains ongoing, with results expected in autumn 2026. GFT has also been contracted to carry out a condition assessment of the penstock, alternatives analysis and detailed engineering design to support its eventual reconstruction.
Yuba Water said the overall recovery will take place in phases over several years, with the timing and cost of the penstock repairs dependent in part on the findings of the condition assessment and forensic investigation.
The agency is currently funding response and recovery work from its financial reserves while evaluating longer-term cost recovery and funding options.
