On October 15, 2026, the California Department of Industrial Relations announced that Cal/OSHA cited two employers a combined $212,500 in proposed penalties following a fatal tunnel collapse near Knights Ferry. The citations were issued September 30, 2026, by Cal/OSHA's Mining and Tunneling Unit after its investigation of the April 14, 2026 collapse about 200 feet inside the Canyon Tunnel construction project, which killed Twyla Capurro, a 35-year-old geologist, and seriously injured another worker. The more than 12,000-foot-long irrigation water diversion tunnel was designed by Provost & Pritchard Engineering Group, Inc. of Clovis and was being constructed by Drill Tech Drilling & Shoring, Inc. of Antioch for the South San Joaquin Irrigation District. Cal/OSHA found both employers allowed work to proceed without removing or adequately supporting identified dangerous ground. 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 plus the same ground control and tunnel support violations. Proposed penalties are not final orders, and citation counts describe what inspectors alleged, not adjudicated facts. Provost & Pritchard has appealed its citations to the Occupational Safety and Health Appeals Board, and Cal/OSHA's Bureau of Investigations is conducting a separate investigation that remains ongoing. For tunneling and heavy-civil crews, the case enforces existing competent-person inspection and ground-support standards rather than creating new ones; employers reviewing their own programs should not treat any appeal outcome as settled until the board rules.