Rust had nearly destroyed much of the invert. Eroded voids were filled with sand and grout, and a new grout invert was poured. |
Prep work is basic, but can't be skipped. In this case, the work was done during a dry time of year and a simple cofferdam was enough diversion for potential stormwater. The pipe invert must be flat enough to allow the spincaster to be withdrawn smoothly, without jerking that would cause uneven grout application. In the case of the Otay Landfill storm sewer, that required filling of the eroded voids with sand and grout, and the pouring of a new grout invert.
PL-8000, made by AP/M Permaform, was used for the invert and the spincasting. The product is a cementitious, fiber-reinforced mortar with excellent properties for CCCP including high strength, quick curing, adherence in moist conditions, and resistance to rust and corrosion.
The pipe above the invert was also repaired as needed to serve as a reasonably firm substrate for the new grout layers, and the corrugated metal pipe was pressure-washed to remove tar and dirt that could affect grout adherence.
With prep work done, the Otay Landfill project became a straightforward CCCP project. The AP/M Permaform crew worked from riser to riser, with a longest pull of about 150 feet. A total of three layers were applied, for a total thickness of 1.25 inches. When working with CMP, as on this project, special effort is made on the first layers to "flatten" the corrugations; this way, the final layer is uniform and smooth.
To guarantee quality and correct application, AP/M Permaform crews check layer thickness with a gauge during the run, and video the entire pipe before and after application.
With prep work and three passes, total time on site was eight days. The result was a clean, strong, rustproof pipe that only reduced the sewer's inner diameter by 2.5 inches.
"This was cost effective, especially compared to trenching," Overton said, "And the quality of the rehabilitation exceeded our expectations."
About the Author: Angus W. Stocking, L.S. is a land surveyor and freelance infrastructure writer. He can be reached at www.InfrastructureWriting.com.