Ship dropped anchor, concerns might have damaged BART's underwater tunnel
Posted by
Gold_12th
on Sat Feb 1 14:20:21 2014
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A strange mishap on the San Francisco Bay Friday morning had a dramatic impact on people deep under the surface riding BART through the Transbay Tube.
A ship suddenly lost power, dropped anchor, and prompted worries it might have damaged the underwater tunnel. The whole thing raised some worrisome questions, but we've found out that the answers are more reassuring.
Just about everything at the bottom of the San Francisco Bay is very clearly charted. On those nautical charts, it is very clearly marked so mariners known not to drop anchors anywhere near the tube.
The Coast Guard says the large container ship was on its way to Berth 35, which is operated by Evergreen Shipping. It lost power, so the pilot aboard dropped anchor to make sure it didn't drift out of control.
According to the San Francisco Bar Pilots, the anchor was dropped 1,200 feet from the Transbay Tube. But even if the tube had been hit, it shouldn't have posed a problem.
"The original criteria called for protection of the underwater portion for exactly those kinds of accidents," engineering consultant Peter Yanev said. "In a port area you could have a boat sink any day so you have to protect against it."
Yanev is an engineer who consulted with seismic retrofitting of the Transbay Tube. It's covered with a 3-foot thick concrete liner.
Trains did stop during the mid-day commute, causing a bit of a stir for passengers.
A BART spokesperson says they inspected the tube during the break and didn't spot any problems so they quickly restarted service.
But they have not released much more information in part because of security concerns.
"You would like to assure the public of what has been done and the details, on the other hand you have people who could take advantage of that," Yanev said.
Crews will inspect the tube again at the end of Friday night's service.
Just like 63rd St. tunnel its an Immersed Tube tunnel, meaning it merely resting on the cleared seabed path, and covered from the top to protect against the incidents such as one mentioned above.
