A 35-year-old geologist and mother of two was killed Tuesday afternoon, April 14, 2026, when part of a tunnel collapsed at a massive water infrastructure project in California’s Sierra foothills. Twyla Capurro of Coulterville was working roughly 200 feet inside the tunnel when rock came loose, trapping her beneath the debris near the Stanislaus-Calaveras county line.
Capurro was pronounced dead at the scene. Her body was recovered from the tunnel around 10 p.m. after hours of painstaking work by more than 30 firefighters from multiple agencies. A second worker escaped before crews arrived and was transported to a local hospital with minor to moderate injuries. A third person caught in the collapse evacuated unharmed.
What Happened at the Canyon Tunnel Project
The collapse was reported at approximately 3:42 p.m. Tuesday at the Canyon Tunnel Project site near the intersection of Schell Road and Sonora Road, northeast of Knights Ferry. The Modesto Fire Department initially dispatched units for a rescue, but the call was quickly upgraded to a technical rescue, bringing additional engines, trucks, squads, and medics from across the region.
A spokesperson for Drill Tech Drilling & Shoring, the primary contractor on the project, said the incident involved “a portion of the tunnel that came loose” and characterized it as something short of a full cave-in. Firefighters had to take precautions against secondary collapses while working in confined, unstable conditions to reach Capurro. The Stanislaus County Sheriff’s Office assisted with drone operations inside the tunnel to provide situational awareness during the recovery effort.
Who Was Twyla Capurro
The Calaveras County Coroner’s Office officially identified the victim on Wednesday as Twyla Capurro, 35, a resident of Coulterville. She worked as a geologist for Provost & Pritchard Consulting Group, the Clovis-based engineering and design firm serving as an advisory group on the Canyon Tunnel Project.
Capurro was a mother to two children, Bodi and Levi, and was engaged to Kyle Lovelady. Friends described her as driven, thoughtful, and deeply committed to both her career and her family. A fundraising page set up by a longtime friend of Lovelady’s had raised roughly $30,000 of its $55,000 goal as of reporting. The organizer said all funds would go directly to Lovelady to help with funeral expenses and immediate living costs.
The $84 Million Project Behind the Tragedy
The Canyon Tunnel Project is a joint effort between the South San Joaquin Irrigation District and the Oakdale Irrigation District. The $84 million project broke ground in August 2025 with the aim of building a 12,106-foot water tunnel to bypass a vulnerable stretch of the century-old Joint Supply Canal near Goodwin Dam. That section of the canal has been repeatedly threatened by rockfalls and landslides, including a 2013 incident that nearly cut off early-season water deliveries to the region.
SSJID is covering 72 percent of the cost, with OID funding the remaining 28 percent. The tunnel was expected to be completed by April 2028. Tunnel work began in January 2026. All work on the project has been suspended following the fatal incident.
Contractor Faces Scrutiny Over Past Incidents
The deadly collapse has drawn attention to the safety record of Drill Tech Drilling & Shoring, the Antioch-based contractor that was awarded the construction contract in July 2025. This was the second fatal incident in five years involving a Drill Tech construction site.
In 2025, a contractor was killed at the New Colgate Powerhouse project in Dobbins when construction equipment fell down an embankment. Drill Tech faces an $18,000 Cal/OSHA fine for that incident and is contesting it. A separate 2021 accident on a Laguna Beach project resulted in a fine that was reduced from $5,000 to $3,500 after the company challenged it before an Administrative Law Judge.
Drill Tech and two of its subsidiaries — Dixon Marine Services and Apex Rockfall Mitigation Work — are all involved in the Canyon Tunnel Project for tunneling, marine construction at Goodwin Reservoir, and rockfall mitigation work.
Investigation Underway
Cal/OSHA investigators were on site Tuesday and were expected to return Wednesday to continue examining what caused the collapse. The two irrigation districts said they would also conduct their own review.
In a joint statement, SSJID and OID said they are “actively participating with all responding and regulatory authorities in their investigation of this matter” and extended condolences to the family and loved ones of those involved. The cause of the collapse has not been determined.