BART halted trains between San Francisco and the East Bay for about 20 minutes around noon today after the Coast Guard alerted the agency about a ship that had dropped anchor near the Transbay Tube.
The Coast Guard called BART at about 11:55 a.m. to inform the transit agency about the incident, in which a ship lost propulsion and dropped its anchor to avoid drifting in the Bay.
BART briefly halted service through the tube so it could inspect the trackway. The agency says no damage has been found, although the tube will be inspected again when the system shuts down overnight tonight.
Service resumed at 12:18 p.m., BART said.
It’s not clear yet what kind of ship was involved or how close the anchor came to the tube. The structure consists of 57 sections and sits in a trench on the floor of the Bay. Its maximum depth beneath the surface is 135 feet.
A story last year in the San Francisco Examiner describes the tube’s protection against the elements and its vulnerability to anchor strikes:
To arm the tunnel’s exterior against the harmful effects of saltwater, the BART tube includes a series of “anode” that are connected by cables along the top of the structure. The electrical charge of the anodes helps convert the steel shell of the tube into a protective layer that doesn’t react negatively to the saltwater, preventing corrosion from eating into the structure.
However, the 30 anodes on the tube jut out nakedly into the water, and the devices are occasionally bashed by a waylaid anchor from one of the innumerable shipping tankers that arrive and depart daily in the Bay, according to BART Assistant General Manager Paul Oversier. The large ships are not supposed to drop anchor above the site, but incidents still occur occasionally.