Cal/OSHA Cites Two Employers $212,500 After Fatal Tunnel Collapse

Highlights

• California regulators proposed a combined $212,500 in penalties against two employers following a fatal tunnel collapse.
• The April 14, 2026, incident killed a 35-year-old geologist and seriously injured another worker.
• Investigators found deficiencies in ground control and tunnel support.
• One of the cited companies, Provost & Pritchard Engineering Group, has appealed its citations.

Investigation Identifies Tunnel Safety Violations

California’s Division of Occupational Safety and Health (Cal/OSHA) has cited Drill Tech Drilling & Shoring Inc. and Provost & Pritchard Engineering Group Inc. for a combined $212,500 in proposed penalties following a tunnel collapse near Knights Ferry that killed one worker and seriously injured another.

The collapse occurred on April 14, 2026, about 200 feet inside the Canyon Tunnel construction project. The victim, Twyla Capurro, a 35-year-old geologist, suffered fatal injuries, while a second employee was seriously injured.

The project involves a more than 12,000-foot irrigation water diversion tunnel designed by Provost & Pritchard Engineering Group and being constructed by Drill Tech for the South San Joaquin Irrigation District.

Cal/OSHA’s Mining and Tunneling Unit issued the citations on Sept. 30, 2026. The investigation found that work continued without dangerous ground being removed or adequately supported and that the tunnel section where employees were working was not securely supported.

Proposed Penalties Address Ground Control and Training

Drill Tech, based in Antioch, received proposed penalties totalling $95,000 for one serious accident-related ground control violation and one willful-serious accident-related tunnel support violation.

Provost & Pritchard, based in Clovis, received proposed penalties of $117,500 for one serious training violation, one serious accident-related ground control violation and one willful-serious accident-related tunnel support violation.

California tunnel safety standards require underground work areas and ground support systems to be inspected by a competent person. Employers must remove or adequately support dangerous ground before other work proceeds, secure underground workplaces and train employees to recognise hazards and appropriate protective measures.

Provost & Pritchard has appealed its citations. Employers may appeal citations and penalty notifications to the Occupational Safety and Health Appeals Board within 15 working days of receiving the notification. A separate investigation by Cal/OSHA’s Bureau of Investigations remains ongoing.

Source: DIR State Of California.