Uptown washout leaves 8-foot-deep sinkhole in Minneapolis intersection
Updated: 1:45 p.m.
A car-sized chunk of pavement collapsed around a manhole on a street in Minneapolis’ Uptown neighborhood over the weekend, leaving a gaping sinkhole.
The city blocked off the intersection of 27th Street and Girard Avenue South to pedestrians and vehicles after the sinkhole appeared on Sunday, although gawkers were walking up to peer into the hole in the pavement.
Crews were digging up the area Monday, in the initial steps of a repair for the sinkhole that city officials said was caused by a collapsed sewer main that runs underneath the street.
“It’s a busy intersection,” said Sean Oberg, supervisor for the City of Minneapolis sewer maintenance group.
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Oberg said there is a 54-inch storm water drain in the area, as well as a 60-inch Metropolitan Council sanitary sewer pipe.
“It’s one of their main interceptors running through the city,” he said.
There are also natural gas lines in the area.
Oberg said such sinkholes aren’t uncommon, and usually happen when a defect opens in a drain pipe of some kind. Infiltrating water at first slowly, then more quickly, washes surrounding fill into the drain pipe and away, sometimes invisibly underground. Warming temperatures can accelerate the process.
Eventually the fill supporting the surface is gone, and a hole opens up.
“We’ve run our camera in our storm sewer. And now we’re going into the sanitary sewer to see if we can see any material, which we haven’t been able to find yet,” Oberg said Monday morning, before the city said a collapsed sewer main was the cause.
Oberg said crews needed to figure out where the defect is first, so that any repairs don’t eventually wash away. The infrastructure will get fixed first, then the area prepared for permanent fill and replacement pavement.
Oberg said it will likely take a number of days to make repairs and make the intersection safe to travel through again.
The damage and repair work isn’t expected to affect drainage or sewer service for businesses or homes in the immediate vicinity.