Missouri’s St. Louis County is adjacent to the St. Louis Metro area, and for most of its history the county was relatively rural and underpopulated, compared to the densely populated city. That changed in the 1960s when the county’s population first exceeded that of the city of St. Louis, and as of 2019 area voters are considering a proposal to merge the two entities.
So it is no surprise that St. Louis County infrastructure management is high-pressure, and the county’s paving maintenance department is always looking for ways to be more efficient and cost-effective. One of those ways is the consistent use of flexible, adjustable manhole risers when raising manholes to grade after paving operations. “We’ve been using them for at least 15 years, and now install anywhere from 150 to 200 annually,” says Paving Maintenance Supervisor Bryan Donovan. “Really, they’re better in every way than our previous riser solution.”
The risers used previously in St. Louis County did have the virtue of being adjustable, but that factor alone was not enough to make them effective. “They were basically older-style four-part cast-iron risers, with sections joined by turnbuckles. But, that meant that each of the four turnbuckles had to be turned with crescent wrenches and the whole riser assembly itself was extremely heavy and slow to install—just a beast to work with.” The cast-iron risers were also not a high-quality solution, according to Donovan. “The old risers would never fit quite right, and we had to use sealant to make them stick. Even then they would sometimes rattle out, especially when they rusted.”
By contrast, the American Highway Products (AHP) Pivoted Turnbuckle Manhole Riser, now in use for 15 years in St. Louis County, is a much lighter, simpler, and more secure solution for raising manholes to grade. Made in Bolivar, Ohio by highly trained staff using advanced robotic welding equipment, they’re a flexible ring made of galvanized U.S. steel joined by just one pivoted turnbuckle. Importantly, this turnbuckle can be tightened with a screwdriver, used as a lever, which is not only more convenient, compared to a crescent wrench, but makes it possible for installers to easily apply several thousand pounds of mechanical force when expanding risers. This guarantees a snug, permanent fit even in old rims that may be worn or out of round—Donovan says that in 15 years his department has never experienced a failure with a properly installed AHP riser. “They’re a lot lighter, easier to work with and store, much quicker to install, and they last longer. We now try to keep about 300 on hand at all times, in two diameters and several thicknesses, so we’re always ready to raise manholes during paving seasons or in emergencies.”
In St. Louis County, many of the older roads have very high crowns; this leads to problems when raising manholes to match steep cambers. In the past, the county has tried to smooth out the transition from level manhole to sloped surface by building in asphalt humps, but this was never really satisfactory. In 2014, the maintenance department ordered six of AHP’s Inclined Manhole Risers to see if a better match was possible. The inclined risers use the same pivoted turnbuckle technology to achieve a secure fit and are also custom-built with inclines—1/4-in. increments from side to side—that make it easy to match sloped surfaces precisely.
“They’ve been in three or four years now, and have held up well while really smoothing out our newly paved roadways,” says Donovan. “And they’re as efficient to install as the risers we’ve been installing for 15 years. So, we’ll be ordering more to have on hand for these situations.”