BNSF Gateway Sub Tunnel #4 is a 480-foot-long (146 m) tunnel on an active BNSF rail line near Quincy, California. The tunnel liner consisted of timber sets and lagging, concrete panels, and steel sets with steel lagging. As a result of the Dixie Fire that ravaged this area in July 2021, the tunnel collapsed and blocked the rail line after the 188 feet (57 m) of timber liner at the tunnel center burned.
Delve Underground provided a conceptual repair design and bid documents within five days of the collapse. BNSF set up a command center to oversee this project, as well as other fire-related projects in the area. The contractor and Delve Underground inspectors worked around the clock, 7 days a week until the tunnel was reopened.
Construction began on the project before the fire was contained in the area, complicating access to the site because of road closures. The site was evacuated twice because of the threat of fire coming back into the area.
Despite the remote location, harsh working conditions in an active fire zone, and supply chain issues encountered nationwide, the tunnel reopened with no reportable injuries in October 2021, a little over 10 weeks after repairs began.
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