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Rehabilitating A New Sewer: Village of Bradley Eliminates I&I With Chemical Grouting
The specific product used was AV-100 from Avanti International, which has some unique features. It’s shipped as liquid or granules and when mixed, its viscosity is quite low, the same as water. That means it will flow anywhere water flows and find its way to the leaks being repaired. Also, its cure time can be manipulated within a wide window, anywhere from five seconds to 10 hours.
In this case, Mauzer mixed the AV-100 thicker than normal, to account for the especially large voids, and timed the solution to set in 12 seconds. Given the high rate of flow through the leaks, this turned out to be the right approach.
Solution grout sets up well in wet conditions; in fact, some flow is necessary to convey the solution to the leak. After oakum packing, and before grout injection, a tracking dye is pumped into the bedding, to verify that injection holes have been drilled in the right area -- if dye isn’t seen coming through the leaks, the drilled hole has to be relocated.
The Visu-Sewer crew worked upstream and actually made two passes; the plugging of initial leaks and some wet weather raised the water level in the trench outside the manholes, making it possible to identify and plug remaining leaks. Mauzer says that the results on this project were particularly gratifying. “You could actually see the leaks slow and stop,” he says. “The village told us that after just three days we'd already cut daily flows by 200,000 gallons -- it was dramatic.”
On average, about 140 gallons of grout were pumped per manhole, which is high compared to similar projects. Quality assurance was straightforward. Bradley inspectors did a visual inspection and the evidence of stopped leaks was quite clear. To complete the job and for “insurance,” loose mortar and visible grout were chipped away from cracks, and the area was patched with a high-strength hydraulic cement mixed on site and made of Portland cement, silica sand and Anti-Hydro, a commercial waterproofing agent.
“The Visu-Sewer crew was very informative,” says Williams. “I was on the site fairly often, and they would always explain what was going on. I appreciated learning more about grouting; it’s an interesting process.”