The Manhattan city government is repairing a 40-foot-wide sinkhole in the Walmart parking lot near Hayes Drive and Bluemont Avenue.
The hole developed over the last couple of weeks above a 36-inch sewer interceptor main carrying sanitary sewer and wastewater flows for more than a third of the city, according to Randy DeWitt, assistant director of public works.
“It’s a pretty important piece of infrastructure,” DeWitt said.
Walmart owns the property where the sinkhole is. The sewer system is still functioning.
“We’re not 100% certain what the exact cause is, but we’re fairly certain there’s a failure in the sanitary sewer system in the area,” DeWitt said.
DeWitt said the sinkhole drops is 3 feet deep in some areas. He estimates it is 40 feet wide.
The majority of the work begins next week, DeWitt said, and city workers plan to dig into the pavement later this week.
“Basically, we’re going into kind of an exploratory phase where we’re going to start pulling up the pavement that’s failed and try to get down to the sanitary sewer that we think has failed, and expose it,” he said. “And then from there, it’s really about fact-finding right now at this point, investigating what’s underground.”
DeWitt estimated the project cost at about $100,000.
“It could potentially be much more,” he said. “No way really to know at this point.”
The Manhattan city government pays for the repairs.
“We’ll accrue the cost through our wastewater fund,” he said.
The area was designated as a FEMA disaster area with potential flooding, DeWitt said, which could provide reimbursements through FEMA assistance.
“At this point, nobody knows if we’ll get a lot of assistance for that because even though we’re in this disaster area, we didn’t actually have any flooding here, so it’s not certain if we’ll get any assistance with that or not,” he said.
DeWitt estimates a time period of 30-60 days to restore the site.
“We don’t anticipate it’s going to be a fast process,” he said.
A local contractor is assisting with the project, DeWitt said. DeWitt did not specify the contractor.
The sinkhole is only affecting the Walmart parking lot area, but DeWitt said the city wants to prevent it affecting other lots.
“What we’re basically trying to do is make sure it doesn’t impact the property south, which would be the Staples and the Hobby Lobby property,” he said.
DeWitt learned about the sinkhole at the end of July.
“It got brought to our attention, and some street department staff went out and put some cones and barriers around it,” he said.