Greater Augusta Utilities District workers clean up after repairing a sinkhole Tuesday on Western Avenue in Augusta. Joe Phelan/Kennebec Journal

AUGUSTA — A small sinkhole identified on Western Avenue was repaired Tuesday after it was reported to the Greater Augusta Utility District.

“Normally, we’d make a repair like this at night, but given the size of the hole, it was an emergency fix,” Brian Tarbuck, Greater Augusta Utility District general manager, said Tuesday, noting it was fortunate no one had driven over the damaged area.

The hole developed in the paving of the left turn lane into the Augusta Plaza near the former Friendly’s on the east end of Western Avenue, a heavily traveled retail and business artery that connects downtown Augusta with Interstate 95.

The sinkhole that formed on Western Avenue in Augusta on Tuesday appeared small on the surface, but was 28 feet deep. It was caused by a failing brick manhole that leaked sewer water. Courtesy of Greater Augusta Utilities District

This is the second sinkhole to form near the utility district’s infrastructure in Augusta in the last two weeks, but the cause of Western Avenue sinkhole is different from the deep sinkhole that recently opened up in a parking lot off Arsenal Street. In that case, water flowed through a corroded storm water pipe, washing away the gravel and sand surrounding it, opening up a hole that was 28 feet deep at its deepest point.

Tarbuck said the top of the hole on Western Avenue was relatively small on initial inspection, about 4 inches in diameter. But when the pavement was removed, workers uncovered a much larger hole, about 2 feet across and 6 feet deep. It was caused by the failure of a an old brick manhole, which is essentially a chimney in the ground.

Over time, he said, the manhole lost a few bricks, causing water from the sewer to flow around the manhole instead of down the pipe, washing away the sand and creating the void.

“In my experience, I’ve don’t think I’ve ever heard of this happening before,” he said. “Normally, we’d backfill with gravel or something, not just sand. A bunch of weird things happened there.”

Tarbuck said manholes today are made of engineered precast concrete that are stacked up on a reinforced concrete base, but decades ago, they were made from brick. He said he’s not sure how old the brick manhole is or how many exist in Augusta.

“There are a number of old manholes on Western Avenue, so this is something we’ll be investigating systematically to see if other manholes are starting to deteriorate like this one,” he said.

Sometimes, the only indication of a problem underground is the appearance of a sinkhole on the surface, he said. And aside from visual inspection, there’s no way to know whether a manhole has failed.

The utility district will continue to monitor the manhole to determine whether it will need to be replaced. A new manhole can cost between $5,000 and $10,000, depending on how deep it is.