A civil lawsuit has been filed over the investigation of a major pipe breach at a Yuba County powerhouse earlier this year that caused significant environmental damage.
Drill Tech-Obayashi Joint Venture (DTOJV) filed suit on June 24 in Yuba County Superior Court, seeking clarification from the court on the responsibility of parties involved and the impartiality of an ongoing third-party investigation.
The company was awarded a $76.8 million contract by the Yuba Water Agency in January 2025 for upgrades to the penstock and Colgate Tunnel at New Colgate Powerhouse.
The penstock, a 14-foot-diameter pipe carrying water to the facility from New Bullards Bar Reservoir, had been drained and taken out of service from September 2025 to February 2026 for the work. It suffered a catastrophic failure on Feb. 13, flooding the powerhouse and forcing workers to evacuate.
The disaster also triggered a major mudslide that swept sediment and debris into the North Yuba River. It also led to the death of hundreds or thousands of juvenile salmon after water levels temporarily dropped.
The lawsuit’s claims
DTOJV’s suit notes the company agreed to perform certain repair work on the penstock. This included construction of certain improvements, removal of a section of the pipe to install new foundations, and installing new vents, among other items.
But DTOJV says it was not directed to reconstruct a shutoff valve which was part of the penstock’s emergency closure system. The complaint says a notice filed by the California Department of Water Resources said the valve was “currently non-operational” and that reconstruction was necessary “so it may be used to reduce discharge in case of a penstock rupture.”
Drill Tech-Obayashi contends that if the valve had been operational and closed in time, significantly less water might have been released during the incident.
The lawsuit says Yuba Water was explicitly responsible for filling, or “rewatering,” the penstock in February 2026, which began days before the catastrophic rupture. DTOJV says it was excluded from “all meetings related to planning and implementation of the rewatering procedure.” The company says its work was suspended immediately after the breach, and its access to the penstock was suspended until May.
DTOJV argues Yuba Water made “operational errors” during the rewatering process including pushing a “high volume” of water through the penstock too quickly, not filling in a segmented process, and using inadequate personnel and resources.
The company alleges the failure happened in a segment Yuba Water chose not to replace. DTOJV says while it welded new air vents and other items on the ruptured segment, “none of these welds exhibited any signs of failure” when inspected in May 2026.
Drill Tech-Obayashi also pointed to a June 4 letter from a Yuba Water attorney as alleged evidence of “Yuba Water’s foregone conclusion to blame the Incident on DTO.”
A portion of the letter cited in the complaint states that while the investigation is ongoing, “it is evident the failure was caused by DTOJV and their subcontractors’ performance, operations or activities,” claiming the company’s welds and installations weakened the penstock.
A Yuba Water spokesperson told CapRadio the agency denies the lawsuit’s claims.
The California Division of Occupational Safety and Health has also launched its own investigation into the Yuba County Water District over the breach.
Independent investigation concerns
Other concerns raised in the lawsuit revolve around an investigation launched in the wake of the disaster.
According to the lawsuit, days after the penstock burst federal officials told Yuba Water to launch an “independent, comprehensive investigation” into the cause of the incident. Yuba Water then hired the third-party consultant SOCOTEC to conduct the investigation.
But Drill Tech-Obayashi alleges Yuba Water is intruding on that impartiality. The company claims a May testing plan from SOCOTEC did not consider several potential failure points, including those DOTJV “alleges were likely caused by Yuba Water.”
The suit also alleges Yuba Water did not disclose any documents in response to a public records act filing from Drill Tech-Obayashi related to the rewatering process, but did provide those documents to SOCOTEC.
“Yuba Water is improperly diverting SOCOTEC’s focus away from the investigation of causes for which Yuba Water is responsible, without providing DTO with access to the records that Yuba Water furnished to SOCOTEC,” the company writes.
It adds that Yuba Water is doing so “in an effort to influence SOCOTEC to render findings adverse to DTO, without considering Yuba Water’s responsibility, while keeping DTO in the dark with respect to many of the facts surrounding the Incident.”
The complaint seeks court action to declare the rights and responsibilities of Drill Tech-Obayashi and Yuba Water regarding the cause of the incident. It also asks for Yuba Water to expand or modify the scope of its testing plan “to address the potential causes for which Yuba Water is responsible.” It does not ask for monetary damages.
A Yuba Water spokesperson said in a written statement the agency will “respect the process of the Independent Forensics Team investigating the incident and will defend it against interference, especially from private parties with an interest in the outcome.”
“We remain committed to an independent, thorough and comprehensive investigation into the root cause of the penstock incident,” the statement adds.
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