By ANGUS W. STOCKING, L.S.
Manholes are durable infrastructure; however, they need to be kept at grade — level with top of pavement — to prevent inflow and infiltration and to avoid roadway degradation and traffic hazards. This can be a real struggle for road crews, particularly if faced with a large system of pipes and manholes. To meet this challenge, cities are turning to American Highway Products’ pivoted turnbuckle manhole risers.
These are sturdy galvanized steel risers, precisely sized to order, that feature a turnbuckle. Using a screwdriver as a lever, the turnbuckle transmits thousands of pounds of force to the flexible rim, seating the riser into original utility rim securely — installation typically takes five minutes or less. And unlike risers that depend on set screws or other mechanisms for adjustment, the pivoted turnbuckle riser connects tightly around its entire circumference, like a pressed in bearing.
Both Milwaukee, Wis., and Jefferson County, Ala., have used the pivoted turnbuckle manhole risers to great success.
Big upside, little downside
“We were having problems in the city with cast-iron manhole risers,” said Milwaukee’s, engineer in charge Samir Amin, P.E. “They’re usually fine, but on occasion they would slip or rattle out, and that led to car damage and claims — there was definitely room for improvement.”
Several years ago, Amin was approached by a representative from American Highway Products, who demonstrated the company’s adjustable riser, the pivoted turnbuckle manhole riser.
It seemed like a good idea to Amin, so he organized a pilot project. “We picked a street that’s near our municipal yards, a street that sees a lot of heavy truck traffic,” he explained. “We set several of the adjustable risers there and just watched over time. They handled heavy loads, and there were no failures or slips, so we were convinced that they would work better than the nonadjustable risers that were being used.”
The city couldn’t specify a particular brand of riser. Instead, Milwaukee wrote specifications for riser use that required adjustable risers with a mechanism similar to the pivoted turnbuckle. That was about four years ago, and the results have been good.
“At the very beginning we faced some resistance from contractors, who were used to the readily available cast-iron risers,” Amin said. “But really, that went away quickly, and now nobody mentions it.”
City crews also install American Highway Products’ risers, including the firm’s catch basin risers, and keep about a hundred risers in inventory for use as needed.
Costs didn’t go up. “Risers aren’t really a big item in most of our mill and fill bids, and I didn’t notice any significant increase in costs due to the required use of adjustable risers,” said Amin.
By now, close to a 1,000 are installed. Milwaukee has emphasized milling and repaving in recent years, and Amin estimated that between two to 300 risers are installed annually. And in all that time, none have rattled out, or failed in any way.
“They’re a successful product, and we’re very happy with them,” said Amin. “They cost a bit more compared to cast-iron risers, but now we have no worries about them coming loose, and that means a lot.”
“We maintain sewers for the whole county, including all the municipalities,” said Jefferson County Commission sewer construction maintenance supervisor Brian Champion, explaining the role of the commission’s environmental services department. “It’s a big job.”
Indeed it is. Home to Birmingham and more than 660,000 residents, Jefferson County is Alabama’s most populous county, and the sewer network Champion maintains includes 3,600 miles of pipe … and 80,000 manholes. That last figure represents a sizable amount of annual maintenance. So whenever Jefferson County roads are paved or repaved, manholes usually need to be raised to match the new roadway thickness. And that responsibility falls to the environmental services department.
“We’re responsible for raising our manholes to grade whenever a road is being repaved,” Champion explained. “The municipalities let us know whenever they have road work scheduled, and we work with contractors to raise the manholes just before paving.”
The amount of manholes raised annually depends on the amount of paving done by municipalities and is unpredictable. Some years the department raises as few as 50 manholes, but fairly often, that number rises to 300 manholes or more. This much variability in annual manhole maintenance costs can be a budget buster, especially if the manholes are raised conventionally by digging out utility frames and building them up with brick and mortar. That process can be a day’s labor for a crew, plus the expense and sustainability costs of hauling waste.
Fortunately, Jefferson County rarely needs to raise manholes the traditional way. “Now and then we still reset manually, but only when the paving lift is about four inches — and that’s unusual,” Champion said. “Most of the time we use the risers.”
The risers are quick and easy to install. “Five to six minutes,” said Champion, adding they are safer for crews due to their relatively light weight while also being very cost effective compared to jackhammering and manual lifting.
And they have a good track record. “We’ve looked at a lot of other options, and nothing else is made or designed as well as these risers — and quality matters,” Champion said. “We keep these in stock and have been using them at least 18 years — the whole time I’ve been here — and I only know of two that have failed. And those weren’t the fault of the riser. One was a freak accident, and one was a rushed installation. Really, we have no complaints.”
Angus W. Stocking, L.S., is a licensed land surveyor who has been writing about infrastructure since 2002.