Making the grade

Roads & Bridges / May 14, 2008

“My history with adjustable risers is that they’ve been very successful,” said Chuck Swan, construction engineer for Norfolk, Va. “As long as the installer cleans out the rim properly, we’ve had no problems with them.”

Swan oversees the repaving of about 30 lane-miles annually, and estimates that 200-300 manholes have to be raised to grade as a result. “Over the years, we’ve tried a bunch of different insert rings, with various degrees of success,” he said.

“The best results have been with adjustable risers, and we’ve been spec’ing them for nine years.” Swan said adjustable risers save money and are durable, and “they’re safer, mainly because they’re so quick to install. If we still had to physically adjust the structures, we’d have to close lanes for two to three days waiting on the concrete to cure. Now, we just pave and go.”

At least one Norfolk-area contractor was already using adjustable risers. Ed Norfleet, operations manager of Virginia-based paving contractor Branscome Inc., said, “I’ve been working with them for 25 years. This is the product we’ve stuck with.” Norfleet’s crews repave up to 500 municipal lane-miles annually and set about 1,500 risers to lift manholes to grade.

The American Highway Products riser is a heavy-duty, galvanized rim that fits into existing utility frames and raises them as needed to match new paving. They’re adjusted up to ½ in. in or out by a “pivoted turnbuckle.” Installers use a screwdriver to crank the turnbuckle and force a snug fit, even when existing frames have worn unevenly or are out of round. “[Adjustable risers] are obviously cheaper than doing this manually. We save cities about $600 per manhole, compared to other methods,” said Norfleet. “They take about five minutes to install and the things that cause delays have nothing to do with the riser. You might have to do some prep work on a casting, clean out buildup with a screwdriver and a hand broom, but that’s it.”

To keep inventory down, Norfleet orders quarterly. “They’re quick on delivery, so I only order what I need. Sometimes they do custom things for me. They always understand what I need and are open to requests.” In Norfolk, according to Swan, the majority of risers used are 24 and 30 in., and an occasional 36 in. The sizing options and adjustability make it easy for contractors to exactly match finished grade; manholes don’t protrude, irritating drivers, and they’re not below grade, causing infiltration problems.

Norfleet agreed that durability is not an issue: “They’re a high-quality product. When they’re sticking up before paving, in high-traffic situations, they’re a little vulnerable to really enormous loads, but by and large damaged risers are negligible.” He also agreed that installing risers is safer for crews and added, “They’re lighter than other alternatives and much less strain to lift.”

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