“It all comes down to the fact that if manholes are just a little too low or a little too high, the traveling public hates them—everyone wants smooth roads!” So says Lee Anderson, public works supervisor in Fargo, North Dakota. He adds, “But of course, we live in the snow belt, and the freezing and the snowplowing are hard on manholes and streets—it took us a while to find a manhole riser solution that stands up to conditions here.”
In Fargo, the Public Works Department doesn’t take on major road rehabilitation projects—that’s the role of the Engineering Department. “Our role is more maintenance and ‘cosmetic’,” Anderson explains, “Basically, we do the light paving and patching that’s needed to keep streets going for a few years before major work is done.” Accordingly, it doesn’t make economic sense to tear out utility frames and rebuild manholes for most projects. But, manholes do need to be flush with new asphalt surfaces. If they’re just a bit low, water collects in the depressed area, and freeze/thaw cycles can do a lot of damage to new pavement in just one winter. And if manhole lids end up raised above the roadway surface, even a little bit, snowplow blades can catch their edges and actually rip them out. It’s a problem.
Fargo experimented with a few different styles of manhole risers. Most had some issues, usually related to the cold. Cast iron risers, for example, weren’t sturdy enough. “We tried cast iron risers, and they’re quite easy to use—you can just set them in place,” says Anderson. “But if they’re just a little bit high, snowplows will catch the edge and flip them out, which usually destroyed the whole manhole.” Fargo also tried rubber risers and adjustment rings, about which Anderson says, “They sure looked nice in June, although they’re a little labor-intensive to install. But in winter, they really fail. They don’t seal well in cold weather, and they stuck to manhole lids; pulling a lid in winter involved sledges and a lot of work. In my opinion, the rubber rings are not a cold weather solution.”
