Editor’s note: This story has been updated to reflect that the Department of Transportation advises motorists to drive slowly over potholes if they aren’t avoidable.
Work on a stretch of the Kenai Spur Highway began earlier than anticipated thanks to a sinkhole that surfaced Tuesday night.
Alaska Department of Transportation and Public Facilities employees spent Wednesday excavating a pothole and underlying sinkhole that formed around mile 12 of the highway between Spruce Street and North Forest Drive in Kenai.
“Basically (Tuesday) night a motorist noticed it, and it’s about 2-3 feet across,” said Shannon McCarthy, public information officer for DOT’s central region.
Lt. Dave Ross with the Kenai Police Department said several calls from drivers began coming in at about 5:49 p.m. Tuesday. Kenai Police responded to the area and helped direct traffic away from the hole while DOT took a look, he said.
Department of Transportation Station Manager Brian Gabriel described the underlying sinkhole as 6 feet deep at its lowest point sloping toward the center of the road and about 15 feet long. McCarthy said that although the sinkhole was cause for concern, there was no way to really know if it would have collapsed in on itself if police had taken longer to clear the two northbound lanes of the road. Sometimes, the road structure itself can help hold the pavement together, she said.
Police on the night shift continued to monitor the hole until Wednesday morning, Ross said.
The culprit for the sinkhole appears to be linked to water, McCarthy said, explaining that it “looks like a pipe had failed” and that water wasn’t flowing through it, creating a void. The hole manifested near a manhole on the road, so DOT employees used that and excavation to investigate. They will fill the hole by laying down fabric, over which they’ll place compacted gravel and a cover, Gabriel said. DOT employees will finish the temporary patch with recycled asphalt, McCarthy said.
It is common for potholes to form in the wake of freeze-thaw conditions, and McCarthy said pothole formation has been pretty active in the state’s central region this winter, though it’s hard to know where they are forming. When it comes to sinkholes, motorists can look for telltale signs other than potholes for clues that something is wrong, she said.
“If you see any kind of deformation of the pavement … like a large soft spot,” she said.
The affected portion of road was already scheduled to be repaved this summer, and will be addressed sometime this construction season, McCarthy said.
She said it is important for motorists to drive slowly over potholes if they can’t be avoided, and to always report both potholes and sinkholes to DOT at 262-2199 and to law enforcement.