Powerhouse pipe burst may take ‘years’ to fix as Yuba County declares emergency

The Yuba Water Agency faces “months to years” of recovery and millions of dollars in lost revenue after last week’s penstock rupture from a mountainous tunnel connecting New Bullards Bar Dam to New Colgate Powerhouse. That has now prompted Yuba County officials to proclaim a local emergency to step up environmental monitoring and coordination in its wake.

The emergency declaration, issued by County Administrator and Director of Emergency Services Kevin Mallen, cited hazardous materials and debris that entered the Yuba River after the Feb. 13 penstock failure and resulting mudslide damaged power generation and distribution equipment.

Water agency and environmental crews have a couple of days of clear weather to continue clearing debris and residue that washed into the Yuba River before another series of storms arrives next week. This week’s storms have complicated cleanup efforts and access to the damaged pipeline and powerhouse.

In proclaiming the emergency, Yuba County leaders said there was no immediate danger to the public and no identified downstream flood risk. The decision made Thursday in Marysville will allow the county to better coordinate with the agency and state and federal partners as cleanup continues. It’s expected to be ratified at Tuesday’s Yuba County Board of Supervisors meeting.

“This is a proactive, coordination-focused step,” a spokesperson for Yuba County said Friday. “The proclamation helps Yuba County more effectively coordinate with Yuba Water Agency and state and federal partners.”

Damage could take ‘months to years’ to fix

The declaration, in effect, accelerates the county’s ability to request additional resources as the agency tackles a restoration process that won’t come overnight.

Officials and engineers have not yet entered the powerhouse because of safety concerns about the stability of the site and the eroded hillside above it. But aerial images of the wreckage and the clean-up efforts taking place downstream at Englebright Dam suggest repairs could take years.

“It’s somewhere between months to years,” Willie Whittlesey, Yuba Water general manager, said of the recovery timeline.

The break occurred as agency workers and contractors were preparing the tunnel and connected pipes for testing. The agency shut down the powerhouse in the fall to replace the 14-foot-wide penstock pipe, a project planned for years and awarded nearly $77 million, leaving the station offline for about four months.

The infrastructure conveys water from the reservoir behind New Bullards Bar Dam to the New Colgate Powerhouse, about 5 miles downstream, where it generates electricity before entering the Yuba River.

Since 2016, the agency has operated the hydroelectric station, which produces power as water moves through the tunnel and penstock to spin turbines at the riverside powerhouse. Pacific Gas & Electric ran the facility for decades and maintains nearby transmission and distribution equipment — which Whittlesey said also appeared damaged.

Revenue from power generation fluctuates with market conditions and hydrology but remains the agency’s largest source of income.

The agency collected about $196 million from electricity sales in the 2024-25 fiscal year, according to a recent budget presentation, with most of that revenue coming from the New Colgate Powerhouse.

What happened in penstock rupture?

The rupture occurred near where the tunnel connects to the 15-foot-diameter penstock, sending a gully of water down both sides of the 1-mile pipeline leading to the powerhouse. The surge washed earth and debris into the river and tore away large sections of hillside.

According to the Federal Energy Regulatory Commission and the water agency, the failure involved a 15-foot-diameter section of penstock pipe between a butterfly valve and a concrete thrust block before the pipe extended down a steep hillside to the powerhouse. The release drained a nearly full, 5-mile tunnel of water stretching back to New Bullards Bar Dam.

The erosion triggered an additional breach and deformation of the pipe and damaged the access road to the powerhouse, cutting off land access, Yuba Water and FERC officials said. Sediment and debris flowed into the Yuba River and continued downstream to Englebright Reservoir, where officials reported working with the U.S. Army Corps of Engineers to manage debris and an oil sheen.

FERC said sediment reached the first floor of the powerhouse and caused substantial damage to the switchyard. The failure also resulted in the loss of power generation and the project’s primary low-level reservoir discharge capacity.

Five workers stationed near the powerhouse were rescued by helicopter from both the New Colgate facility and a nearby Pacific Gas & Electric site after the access road was severed. One worker initially reported missing was later found and taken to a local hospital with serious injuries. The agency reported that he remained hospitalized in stable condition.

Access to the site remains limited

While operations remain unaffected upstream at Bullards Bar, engineers and workers have had limited access to the rupture site, near the tunnel connection uphill from the powerhouse, and have begun a forensic engineering investigation that could take months to complete, Whittlesey said.

The water release is believed to have caused erosion that destabilized pipeline supports, apparently causing some pipe sections to separate. But the initial rupture appears to have occurred closer to where the tunnel and pipe connect at the top of the hill.

Water in the tunnel came from the reservoir behind New Bullards Bar Dam, but was introduced through a series of valves that allowed the tunnel to fill without opening the full reservoir, which was not damaged.

“The tunnel was nearly full, but there was no way for the water to leave the reservoir and get into the tunnel during the incident,” Whittlesey said.

In its Feb. 17 letter, FERC gave Yuba Water Agency 10 days — until Feb. 27 — to submit plans detailing how it will operate New Bullards Bar Dam without the penstock and to begin an independent forensic investigation into the failure.

FERC, an independent federal agency that regulates hydroelectric projects and energy markets, also ordered the agency to convene an independent board of consultants to oversee design and reconstruction of the damaged penstock, tunnel and powerhouse.

Fixing a penstock pipe?

Part of the penstock improvement project included installing a new protective valve where the tunnel meets the penstock system, officials said when the project was announced. The agency has planned the replacement since 2017 and worked with contractors and manufacturers to build specialized equipment for the dam and powerhouse.

“Every hydroelectric generating project is unique, they were built at different times with different technologies,” Whittlesey said. “… I think one of the biggest issues we have is, we don’t know what our long lead items will be because we don’t know the condition of them.”

Had the new infrastructure been installed and tested, the powerhouse could have resumed operations within weeks.

Now the agency is developing an adjusted conveyance plan to manage water releases from the reservoir without the 5-mile tunnel and pipeline network that fed the powerhouse — its primary method of regulating Yuba River flows, particularly during the dry season.

“Right now we’re releasing water through the spillway and there will be limitations on how we convey water through the dam later in the season once the water decreases to below the crest of the spillway,” Whittlesey said.

This story was originally published February 20, 2026 at 11:36 AM.