Cal/OSHA Proposes $212,500 in Penalties Following Fatal Tunnel Collapse -- Occupational Health & Safety

Cal/OSHA Proposes $212,500 in Penalties Following Fatal Tunnel Collapse

Two employers were cited for alleged ground support and safety violations after a tunnel collapse killed one worker and seriously injured another.

By Stasia DeMarco
Oct 15, 2026

Cal/OSHA has proposed $212,500 in penalties against two employers following a tunnel collapse near Knights Ferry, California, that killed one worker and seriously injured another.

The April 14, 2026, collapse occurred approximately 200 feet inside the Canyon Tunnel construction project, trapping two workers. Twyla Capurro, a 35-year-old geologist, suffered fatal injuries, while another worker was seriously injured.

According to Cal/OSHA, the employers failed to provide adequate ground support in areas where dangerous ground conditions had been identified.

Provost & Pritchard Engineering Group Inc. designed the more than 12,000-foot-long irrigation water diversion tunnel, and Drill Tech Drilling & Shoring Inc. was constructing it for the South San Joaquin Irrigation District.

Cal/OSHA's Mining and Tunneling Unit issued citations Sept. 30 following an investigation into the collapse.

Drill Tech Drilling & Shoring, based in Antioch, faces $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, based in Clovis, faces $117,500 in proposed penalties for three violations involving employee training, ground control and tunnel support. The citations include one serious training violation, one serious accident-related violation and one willful-serious accident-related violation.

California's tunnel safety standards require a competent person to inspect underground work areas and ground support systems upon initial entry and frequently afterward. Employers must remove or adequately support dangerous ground before allowing work to proceed and ensure workers receive appropriate hazard recognition training.

Cal/OSHA Chief Debra Lee emphasized the importance of proper tunnel support and safety measures to prevent workers from being buried or crushed during a collapse.

Provost & Pritchard has appealed its citations. Cal/OSHA's Bureau of Investigations is conducting a separate, ongoing investigation.

About the Author

Stasia DeMarco is the content editor of Occupational Health & Safety.

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