When ‘Old School’ is the Right School: Combined Grout, CIPP Effective Solution For Illinois City

January 2013, Vol. 68, No. 1

On average, about 21 gallons of grout were used on each 108-inch joint, depending on how much grout was accepted under high-pressure pumping. The acrylamide grout was pumped through joint leaks, under pressure, so that it completely filled voids in the soil outside the pipe. It then set permanently into a solid but flexible exterior band that seals the leaks, stabilizes the pipe, and permanently fills voids to minimize groundwater flow around the joints. A small grout band was left on the inside of the pipe and could easily be removed.

Quality assurance was provided by continuous onsite inspection, continuous video recording and the air testing which preceded and followed all joint rehabilitation. Osborn says the only real hitch happened during summer months when “the trailer got a little warm!”

One of the biggest dangers of sewer work is the air quality hazards of confined spaces. Walden Associated Technologies has gone to extraordinary lengths to ensure a safe working environment. Each crewmember is certified in confined space rescue and carries an air monitor at all times. Air is also monitored remotely during work. Ten-minute escape tanks and 30-minute breathing apparatuses are attached to custom brackets right on the packers. Audio and visual monitoring from the grout trailer was hardwired and continuous.

Weather was also monitored to guard against sudden storm water rises in pipes. “We actually had a surprise rainstorm come through one day,” says Bohn, “We immediately pulled our crews and the packer and other equipment out. Fortunately, what we found was that it takes an hour or so for the water level to rise significantly, even in a heavy rainstorm -- still, there was some intense scrambling and we’re glad we had the policy in place.”

More to do
Project B is completed, with all joints successfully passing air testing. But in the course of work, a surprise was uncovered -- about 2,000 lineal feet of 112-inch cast-in-place pipe. This pipe has no circular joints. Instead, it has long seams that run along the pipe sections at 3 and 9 o’clock. “They would pour the bottom half, and let it set,” Bohn explains, “Then frame up the top half, and pour that.”

Like the rest of the system, this pipe is also about 100-years old, with lots of leaks and gaps along the seams. Osborn says it will also be grouted; “We’re looking at our options,” he says, “But it’s in generally good condition, for 100-year old pipe, and we feel grouting will work well.”

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