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As the superintendent of the City of Minot’s Water and Sewer Department, John Reynolds is very familiar with the problems caused by North Dakota’s constant freezing and thawing cycles.
If drivers notice what appear to be sunken manholes in various locations in Minot, thank Mother Nature.
But do the manholes actually sink? No.
“Because of the freeze/thaw cycles in North Dakota, the frost will heave the subgrade and asphalt up as the materials expand,” Reynolds said. “The actual manhole doesn’t move. Some of the voids can be three or four inches deep. If the actual manhole sank that far, we would have serious water drainage issues down in the manhole.”
The solution? Well, actually there are a couple of ways to fix the problem.
For a temporary repair, crews will install as many rubber spacers as necessary to fill the void. The spacers are one inch thick, and help eliminate the void until a more permanent fix is possible. They may also place sand or gravel on top of the manhole covers, as a temporary measure until the ground around the manholes settles.
“For permanent repairs, we’ll adjust the actual casting of the manhole, which is what the manhole cover sits on,” Reynolds said. “We’ll remove some of the asphalt around the manhole, install spacers underneath the casting and then put it all back together, including new asphalt around the manhole cover.”
Reynolds said if drivers notice sunken manholes, they can report the location to the Public Works Department at 857-4140 or the Water and Sewer Department at 857-4150
“It varies from year to year, depending on how severe the temperature changes are that year,” Reynolds said. “Some of the smaller ones will settle back down when temperatures rise, but for most of them, once the pavement is compromised, we need to repair them.”