St. Louis finds a manhole rim-raising solution that stands up to time and traffic.
With a population of about 320,000, St. Louis, Missouri, is the 60th largest city in the U.S. But due to an unusual arrangement, St. Louis, its metro area (population about 3 million), and surrounding St. Louis County (about 1 million) happens to be served by the fourth-largest sewer district in the U.S., just behind New York, Los Angeles and Chicago.
“We’re odd,” says Jonathon Sprague, director of operations for the Metropolitan St. Louis Sewer District. “We cover the city and county of St. Louis, and about 90 small municipalities. So it’s an extreme-ly large system, and we have to be efficient — ideally, we only want to do a job once, and not have to come back for a long time.”
There are 160,000 manholes in the MSLSD system. With that many manholes, and with the constant amount of street work and repaving required in any metro area, raising manholes to grade is a major task, performed thousands of times annually, according to Sprague. In accordance with his belief in doing a job once, Sprague wanted a manhole-raising solution that was durable and permanent.
The water department first tested the American Highway Products Pivoted Turnbuckle Manhole Riser in 1996, which was a major change in policy — the department had given up on the use of risers after cast iron products had proven to be ineffective and unsafe. “We could never get them to seat well,” says Vince Foggie, St. Louis Water Department superintendent, referring to the nonadjustable cast iron risers. “They’d rattle and even pop out at times, leaving the traffic and the public exposed to an open manhole — it was dangerous.”
For several years after they quit using cast iron risers, water department crews raised manholes to grade by manually exposing and lifting concrete grade rings, a process that takes several hours and compromises new paving lifts — after jackhammering and raising, the newly raised rims have to be sealed in with new concrete, creating seams in the new pavement that wear faster than undamaged concrete. It was clearly a problem, so it made sense to do a pilot test with an adjustable riser.
The American Highway Products riser relies on a pivoted turnbuckle that can be expanded with a screwdriver. “For the pilot test, we put a riser in an intersection on Kingshighway Boulevard, one of our busiest downtown roads,” Foggie explains. “It was easy to install, stayed put and didn’t cause any problems, and it didn’t rattle. It was very encouraging, especially since we were getting behind on paving at the time.”
Given the sheer scale of manhole raising in MSLSD, there was a significant opportunity to save money and time. For both those reasons, the pivoted riser has proven to be the MSLSD’s preferred solution for raising manholes.
“We’ve been using them a long time, more than 15 years,” Foggie says. “And in all that time, we’ve only had one fail — and that’s because we installed it in a worn frame that we should have replaced. When we did, we had no problems.”
Sturdy but flexible
The turnbuckle exerts thousands of pounds of mechanical force, seating the riser with absolute security even if rims are worn or out of round. The turnbuckles can also be loosened, which is useful in St. Louis.
“We looked at risers that are glued in, and decided they were no good,” Sprague explains. “Because then they’re hard to remove when we come back in a few years. It’s possible to stack the AHP risers, but I prefer not to do that. With the turnbuckle, we can just loosen the riser installed for the first paving lift, and replace it with a taller riser that will match the total height of new paving after the second lift — it’s very convenient.”
Riser heights start at 3/4 inch and increase in 1/4-inch increments. Likewise, risers can also be ordered in whatever diameters are needed, and are shipped fully assembled. Since they’re relatively lightweight and stackable, they’re easy to keep on hand. Custom-sized risers are also available.
Now, the department keeps risers on hand in several different thicknesses, and installs 200 to 300 annually, and even more in a heavy paving season. “They save us thousands of dollars,” Foggie says. “And more important, they save labor. I don’t have to assign a crew to spend hours following a paving truck, and that means they can be doing water department business.” The city also specifies that the risers be used on state paving projects within city limits.
In addition to repaving projects, St. Louis also uses the AHP risers anywhere a manhole is below grade, creating a pothole. They make maintenance easier, and since virtually all of the city’s manholes are at grade, snowplows don’t catch rims and cause damage.
For many reasons, the AHP risers are also safer; they’re lighter, which reduces pinch and strain injuries; they don’t rattle loose and expose drivers to open manholes; and they’re quicker to install, which reduces crew exposure to traffic.
“They only take 10 to 15 minutes to install, and we don’t have to remove any material or fill in with mix,” Sprague says. “Usually, we only have to close traffic down for a half-hour or less. So they keep my crews and the public safer.”