Cal/OSHA Cites Two Employers $212,500 After Fatal Canyon Tunnel Collapse Near Knights Ferry
SACRAMENTO — Cal/OSHA has cited two employers a combined $212,500 in proposed penalties following an April 14, 2026 tunnel collapse near Knights Ferry that killed one worker and seriously injured another, the California Department of Industrial Relations announced on October 15. The collapse occurred 200 feet inside the Canyon Tunnel construction project, trapping two employees. Twyla Capurro, a 35-year-old geologist, suffered fatal injuries, while another worker was seriously injured.
The more than 12,000-foot-long irrigation water diversion tunnel was designed by Provost & Pritchard Engineering Group, Inc. of Clovis and was being built by Drill Tech Drilling & Shoring, Inc. of Antioch 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, and 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 citations. Drill Tech 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 was cited $117,500 for one serious training violation, one serious accident-related ground control violation and one willful-serious accident-related tunnel support violation. Provost & Pritchard has appealed the citations. Cal/OSHA's Bureau of Investigations is conducting a separate investigation, which remains ongoing.
"Deaths and serious injuries from tunnel collapses are entirely preventable," said Cal/OSHA Chief Debra Lee. "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."
According to the project owners, the roughly $84 million Canyon Tunnel, jointly built by the South San Joaquin and Oakdale irrigation districts, runs about 12,106 feet and will bypass a vulnerable reach of the Joint Supply Canal carrying water from Goodwin Dam on the Stanislaus River. The construction contract was awarded to Drill Tech in July 2025, and work began that August.
Published by GSM · USA (original Chinese edition)
Photo: 图：骑士渡廊桥横跨斯坦尼斯劳斯河，峡谷隧道工程即位于骑士渡附近（资料图，Wikimedia Commons，公共领域）。Knights Ferry covered bridge over the Stanislaus River, near the Canyon Tunnel project site (file photo, Wikimedia Commons, public domain).
