Cal/OSHA cites two employers $212,500 following fatal tunnel collapse
Sacramento— Cal/OSHA has cited two employers $212,500 in penalties following a tunnel collapse near Knights Ferry that killed one worker and seriously injured another. The investigation found that both employers failed to provide adequate ground support to protect employees working in the tunnel.
What Happened: On April 14, 2026, a collapse 200 feet inside the Canyon Tunnel construction project trapped two employees. Twyla Capurro, a 35-year-old geologist, suffered fatal injuries, while another worker was seriously injured.
What Cal/OSHA Chief Debra Lee said: “Deaths and serious injuries from tunnel collapses are entirely preventable. Cal/OSHA consistently reminds employers of the need to provide adequate support and safety measures to protect workers from being buried or crushed in a sudden collapse. There is absolutely no justification for putting a worker’s life at risk.”
The more than 12,000-foot-long irrigation water diversion tunnel was designed by Provost & Pritchard Engineering Group, Inc. and was being constructed by Drill Tech Drilling & Shoring, Inc. for the South San Joaquin Irrigation District.
Cal/OSHA found that both employers allowed work to proceed without removing or adequately supporting identified dangerous ground. They also failed to securely support the tunnel section where employees were working, resulting in the collapse.
On September 30, 2026, Cal/OSHA’s Mining and Tunneling Unit issued the following citations and proposed penalties:
- Drill Tech Drilling & Shoring, Inc., based in Antioch, was cited $95,000 in proposed penalties for one serious accident-related ground control violation and one willful-serious accident-related tunnel support violation.
- Provost & Pritchard Engineering Group, Inc., based in Clovis, was cited $117,500 in proposed penalties for one serious training violation, one serious accident-related ground control violation and one willful-serious accident-related tunnel support violation.
California’s tunnel safety standards require underground work areas and ground support systems to be inspected by a competent person upon initial entry and frequently afterward. Dangerous ground must be removed or adequately supported before other activities proceed, and underground workplaces must be securely supported. Employers must also assess employees’ experience and provide instruction on recognizing hazards and the protective measures needed to address them.
Employers have the right to appeal any Cal/OSHA citation and notification of penalty by filing an appeal with the Occupational Safety and Health Appeals Board within 15 working days from the receipt of notification.
In this case Provost & Pritchard Engineering Group, Inc. has appealed the citations.
Cal/OSHA’s Bureau of Investigations is conducting a separate investigation, which remains ongoing.
About Cal/OSHA
Within the Department of Industrial Relations, Cal/OSHA helps protect workers from health and safety hazards on the job in almost every workplace in California.
Workers in California are protected regardless of immigration status. Workers who have questions about safety and health in the workplace can call 833-579-0927 to speak with a live bilingual Cal/OSHA representative between the hours of 9:00 a.m. and 7:00 p.m. Monday through Friday. Complaints about workplace safety and health hazards can be filed confidentially with Cal/OSHA district offices.
Employers who have questions or need assistance with workplace health and safety programs can call Cal/OSHA’s Consultation Services Branch at 800-963-9424 or their local Cal/OSHA Consultation Office, or email InfoCons@dir.ca.gov.
Media Contact: Communications@dir.ca.gov, (510) 286-1161