Manholes precisely at grade make better streets in St. Charles, Mo.

April 05, 2019
St. Charles, Missouri; adjustable manhole risers

With a population of 66,000, St. Charles is Missouri’s ninth-largest city, and was the state’s capital from 1821 to 1826.

“We have old and new areas, which means we have a lot of odd-sized sewer structures,” the city's Lead Equipment Operator Cory Rackley said. “Adjustable risers make it much easier to raise all these differently sized manholes to grade.”

Rackley maintains the city’s sanitary and storm sewer networks, and is responsible for keeping about 10,000 manholes precisely at grade. If they are too low, citizens and council members complain. But if they are too high, even by as little as a quarter inch, snowplows will catch and tear them out.

For years, his crews raised manholes to grade after new paving with traditional methods that required excavation and the use of concrete rings or bricks. But since 2008, he has been using Pivoted Turnbuckle Adjustable Manhole Risers, made by American Highway Products (AHP), to raise manholes precisely to grade without excavation, without significant traffic closures, and without the need for equipment to lift and set heavy concrete rings. “When we have a manhole to raise now, we can do it in half an hour or less, depending on traffic, without stopping traffic or digging up pavement,” Rackley said. “Compared to that, the concrete rings were a nightmare—they’d take one to two days, and usually required detours.”

The AHP adjustable riser is a flexible, galvanized ring made with American steel that uses a turnbuckle to adjust riser diameter. For the installation process, one man sets the riser in original utility rims and uses a screwdriver as a lever to expand it to fit. Since the turnbuckle leverage applies thousands of pounds of force, the riser seats in the rim tightly, providing a new rim for the manhole with no rattling or looseness.

City crews set 40 or more of the AHP risers annually, and contractors set about the same amount. Sometimes, the city has to redo contractor work. “They’re responsible for getting manholes to grade, but sometimes we can’t have an engineer or inspector on hand, and they aren’t as close as we’d like. And sometimes compaction is bad, and settling causes manholes to sink a bit,” Rackley explained. “When that happens, we’re able to replace the riser with one that’s slightly taller, and bill the contractor. And we’re usually able to reuse the riser that comes out.”

The city also keeps risers on hand, in multiple sizes, for their own use, and occasionally for contractors. In the last year, Rackley also has started using inclined risers, a newer product from American Highway Products. These help make an even closer match to the final road surface.

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