Long before Caltrans announced Tuesday night it was planning to close the Caldecott Tunnel due to planned PG&E outages, there were already signs a major power outage could cripple the tunnel.
State inspectors, using guidelines established by the U.S. Department of Transportation, found significant issues last year with the Caldecott Tunnel’s emergency power distribution systems, which are designed to provide uninterrupted power in the event of an outage.
The inspection was part of 2015 Department of Transportation initiative to evaluate the safety of the country’s tunnels. As part of that program, inspectors looked at dozens of tunnels in California, scrutinizing structural safety and system functions.
The Caldecott Tunnel was one of only three tunnels in the state to receive a rating of severe for its ‘Emergency Distribution Systems,’ the lowest possible score inspectors can give, according to data on the Department of Transportation's website. The systems include backup generators and other equipment that would supply emergency power in the event of an outage.
Detailed reports are unavailable online, so it’s unclear exactly what inspectors found to be so problematic. A spokesperson with Caltrans said they were aware of the low ratings for the emergency distribution systems, but could not provide additional details at this time.
However, the Department of Transportation's Tunnel Operations, Maintenance, Inspection, and Evaluation Manual explains how emergency power distribution systems are typically tested. The procedures call for inspectors to disable the normal power supply to the tunnel and evaluate how the emergency system performs.
The low scores for the Caldecott indicate many of the tunnel's emergency power systems performed poorly during that test, to the point where the tunnel may not be functional if it were to lose power from the grid.
While the tunnel is equipped with backup generators, a Caltrans spokesperson said those generators are only able to power the lights and security cameras in the event of an outage, but it's not designed to keep the ventilation systems working. As a result, Caltrans announced Tuesday night that it might have to close the tunnel if PG&E cut power to the area.
That scenario was averted Wednesday morning as Caltrans managed to install temporary generators overnight that could power the ventilation systems if the substations on both sides of the tunnel were shut down. A spokesperson for Caltrans acknowledged the system isn’t perfect, but said they are working on a permanent solution in the form of a new generator that they plan to install by 2020.