KNIGHTS FERRY NEWS | STANISLAUS COUNTY | October 18, 2026. California workplace safety officials say unsafe underground conditions contributed to a fatal tunnel collapse near Knights Ferry earlier this year. Cal/OSHA announced October 15 a total of $212,500 in proposed penalties against two employers associated with the Canyon Tunnel construction project. One worker died and a second was seriously injured in the April 14 incident.
The agency’s findings and citations are significant, but the distinction between proposed regulatory penalties and a final unappealable judgment matters. One company has already appealed, and a separate investigation by Cal/OSHA’s Bureau of Investigations remains ongoing.
What happened inside the tunnel?
The regulator says the April 14, 2026 collapse took place roughly 200 feet inside the Canyon Tunnel, a water-diversion project more than 12,000 feet long intended for the South San Joaquin Irrigation District. Two workers were trapped. Twyla Capurro, a 35-year-old geologist, was killed, and another employee suffered serious injuries. The agency’s findings concern the jobsite’s ground-support systems and workers’ exposure to dangerous rock and soil conditions.
State officials identified Drill Tech Drilling & Shoring Inc. as the construction contractor and Provost & Pritchard Engineering Group Inc. as the project’s designer. Cal/OSHA alleges that the employers permitted underground work without removing or adequately supporting identified dangerous ground and failed to secure a section where employees were working.
What penalties were announced?
- Drill Tech Drilling & Shoring, Antioch: $95,000 in proposed penalties for a serious accident-related ground-control violation and a willful-serious accident-related support violation, according to Cal/OSHA.
- Provost & Pritchard Engineering Group, Clovis: $117,500 in proposed penalties involving a serious training violation, a serious accident-related ground-control violation and a willful-serious accident-related support violation.
These two amounts total $212,500. They should not be described as money already paid, damages awarded to the victim’s family, or funds earmarked for affected workers. Citations can be contested, and enforcement outcomes may change through the administrative process.
What is the status of the case?
Cal/OSHA reports that its Mining and Tunneling Unit issued citations September 30. Provost & Pritchard has appealed its citations, according to the October 15 announcement. Employers generally have 15 working days from receipt of a notice to appeal to the Occupational Safety and Health Appeals Board. A separate Bureau of Investigations inquiry remains active. California58 has not received independently verified final decisions resolving every citation.
Why tunnel support is critical
Underground construction is particularly sensitive to conditions that can change as excavation advances. California’s tunneling standards require dangerous ground to be removed or supported; work areas and supports must be inspected by competent personnel upon initial entry and regularly afterward. Employers also must assess workers’ experience and train them to recognize ground hazards.
This story concerns an industrial workplace incident at the Canyon Tunnel. It is not a report that the tourist area, historic Knights Ferry Covered Bridge or the general community is under a collapse warning. Residents looking for separate recreation updates can read our existing report on the covered bridge and Stanislaus River Parks.
How workers can obtain help
Cal/OSHA says workers may seek information or file a workplace safety complaint regardless of immigration status. Its bilingual information line is 833-579-0927, staffed Monday–Friday, 9 a.m.–7 p.m., according to the state. To verify the case and its findings, read DIR Release 2026-83 and follow the relevant administrative proceedings.
Source: California Department of Industrial Relations, Cal/OSHA news release dated October 15, 2026. This article attributes its findings to the regulator, names the appeal and ongoing investigation, and does not represent allegations as a final court verdict.
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