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When ‘Old School’ is the Right School: Combined Grout, CIPP Effective Solution For Illinois City
A different technique will be used for this sewer pipe. Instead of setting up packers, holes will be drilled along the seams and acrylamide grout will be injected with hand-held injection guns connected by hoses to the grouting trailer. But as with the packing technique, grout will still set up outside the pipe, filling the soil voids that exacerbate sewer leaks.
The Granite City Sewer Lining and Rehabilitation Project combines two types of rehabilitation techniques, CIPP and chemical grouting, as a means to maximize the footage rehabilitated within the available dollars. This approach makes perfect sense and is becoming more frequent; CIPP is fast and cost-effective in smaller pipes, but can become expensive for larger diameter pipe. “We talked to suppliers and found that CIPP would have worked for the larger diameters,” says Osborn, “But sewer grouting was just as effective in this situation, and much more economical at larger sizes. It was fast, we could test it for quality assurance immediately after application, and it will seal the joints effectively for a long time.”
Looking just at the 108-inch pipe, costs for joint testing, sealing labor and materials, taken from the project's official bid tab, totaled $610 per joint. There were minor changes in the actual final contract price due to changes in field conditions. There was a total of 3,600 lineal feet of 108-inch pipe, which contained 600 joints for a cost of $366,000.
In terms of 'feet per dollar,' it's clear that grout sealing joints when possible comes out ahead of total pipe replacement for the large diameter pipe. This isn't the whole story of course, because it isn't really an 'apples to apples' comparison; after all, a sewer rehabilitated with CIPP is essentially new pipe from start to end. But Granite City engineers had determined that the pipe itself was structurally sound and that leaking was confined to joints. That being true, there was a compelling case for simply sealing the joints with solution grouting, which salvaged the existing pipe by using grout to stop infiltration and stabilize the 108-inch sewer pipe bedding soil.