Sinkhole restricts traffic on inbound lanes of Glenn Highway in East Anchorage

Update, 3 p.m. Friday: Crews are working to put down temporary pavement at the site of a large sinkhole caused by an old, wooden septic system underneath the Glenn Highway in East Anchorage, a Department of Transportation official said.

“As soon as rush hour traffic died down right around 9 a.m., we went back out there, closed off the two lanes again and excavated the hole,” DOT spokesperson Shannon McCarthy said.

Crews went down 16 feet and found that the septic system, otherwise known as a “crib,” was collapsing, according to McCarthy.

A contractor will pave early next week, she said.

Update, 7:45 a.m.: Crews temporarily patched a sinkhole that appeared in the Glenn Highway by 5 p.m. Thursday, according to state Department of Transportation spokeswoman Shannon McCarthy. They plan to return to the site Friday morning after rush hour and dig it out, fill it in, and compact it.

It’s possible work may continue on Monday, with paving, but that decision depends on how much excavating is necessary.

It appears the hole was caused by an old, wooden septic system -- known as a “crib” -- beneath the road surface, McCarthy said. “They were buried deep and hard to detect.”

Original story: A large sinkhole closed two inbound lanes of the Glenn Highway on Thursday in East Anchorage, a transportation official said.

A depression in the pavement was noticed around 10:30 a.m. in the middle inbound lane of the highway west of the McCarrey Street overpass, said Shannon McCarthy, a spokeswoman for the state Department of Transportation.

“We tested it out real quick and discovered there was a sinkhole underneath it,” McCarthy said.

In order for crews to work safely in the area, both the middle and far right inbound lanes of the highway were closed, she said. Crews were working Thursday to create a temporary repair, and McCarthy said the goal is to have the lanes reopen by Friday morning.

It was not immediately clear what caused the sinkhole, but McCarthy said the situation may similar to what happened with a sinkhole that formed in May on Fifth Avenue near Merrill Field. That sinkhole was caused by a decades-old wooden septic system associated with homes that once existed in the area.

“It’s obviously an area that had been settled some 50, 60, 70 years ago, so there’s bound to be some stuff that’s far underneath the road that we weren’t aware of,” she said.

Maintenance crews will have to go back to the sinkhole at a separate time to figure out what caused it and make a permanent repair, but McCarthy said they hope to find a way to do the work when it will cause less of an impact to traffic.

Only one inbound lane of the Glenn Highway was set to remain open Thursday night, likely causing traffic delays. McCarthy advised drivers to seek out alternate routes if possible.