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When ‘Old School’ is the Right School: Combined Grout, CIPP Effective Solution For Illinois City
Why the reversion to an ‘old school’ technology? Osborn says it has everything to do with cost-effectiveness; “For large diameter pipes that are structurally sound, grouting is just as viable a solution, and it’s considerably more economical,” he says, “Especially for pipe bigger than 54-inches, the cost of handling and installing large liners gets expensive.”
Where CIPP is used to reline entire sections of pipe, from manhole to manhole, chemical grout is used to repair leaks and gaps where they actually occur, at joints. Since segments of large diameter concrete sewer pipe are only three to 8-feet long, several thousand joints needed to be sealed. This work is done with large, collar-like devices called packers.
Packers are quite versatile. In addition to pumping chemical grout into joint openings, they can also be used to air test joints. The basic work procedure was to lower the packer sections through the manhole and reassemble the packer at the bottom of the manhole. Once assembled, the packer could be moved between joints as needed for the test and seal operations. Each joint was air tested for soundness. Less than 1 percent of Granite City’s sewer joints passed.
For the joints that did not pass air testing, the packer was then used to pump solution grout until the soil could no longer absorb additional grout, known as refusal. After allowing the grout to set (or gel) for an additional 90 seconds, the packer was deflated, reinflated on the joint and used again for air testing to confirm that the joint had been sealed.
But packers do need to be sized to fit the pipe, which was a minor challenge for Walden Associated Technologies. “We had access to all sizes of packers that we needed, except for the 108-inch packer,” explains Walden’s Estimator and Project Manager James Bohn, “We had to have that one custom-fabricated for this project.” The custom, 108-inch packer was built by Logiball Inc. “We’ve already used that packer on several hundred joints,” says Bohn.