The flooding that shut down an important highway tunnel in Boston Wednesday night was a dramatic but rare occurrence, Massachusetts' top highway official said in an update on what happened.
About 130,000 gallons of water filled three feet of the tunnel, the connector between interstates 90 and 93, starting about 7 p.m. Wednesday, Massachusetts Highway Administrator Jonathan Gulliver said Thursday. The water came from storm runoff as the area received about four inches of rain, much of it falling just at the start of rush hour.
"This was a huge storm that hit us very intense," Gulliver said.
Viral videos had showed cars driving through a flooded tunnel, and state police confirmed that night that the Congress Street I-93 on-ramp was closed due to flooding. Gulliver said that more of the highway was closed because of the flooding covering 400 feet of roadway at the I-90/I-93 split, where the two major highways divide under Boston, near South Station.
When the highway started flooding to the extent it did, it was a shock — MassDOT officials said nothing like it had happened in recent memory.
"We saw it on social media -- we have cameras here too. But certainly the [video] that was making the rounds last night was pretty dramatic," Gulliver said. "It's a pretty big deal to see something like that."
While officials initially thought the flooding was caused by a pump station failure, they found that it was instead a clog in a drain, "a more extensive issue than we had initially expected," Gulliver said.
It took until 11:30 p.m. for the road to reopen, but there was no lasting damage.
Asked for a message to people who saw the video and might be worried about driving through the tunnel, Gulliver said, "That was a very dramatic video, but I want to ensure people that the tunnel systems we have are safe ... this is a very isolated incident that we don't expect to have happen again."
The intense storm that hit Boston Wednesday also knocked out power for tens of thousands.
