New Technology Saves a Sewer Interceptor—and $1.5 Million!

By Angus W. Stocking, L.S. | January 2011 Vol. 66 No. 1

Centri-Pipe (centrifugally-cast concrete pipe) lining technology is offered by AP/M Permaform. In essence, Centri-Pipe is a way to centrifugally apply a layer or multiple layers of high-strength structural grout onto deteriorated pipe interiors at diameters ranging from 30-inches to 120-inches. The grout products developed by AP/M Permaform are designed specifically for structural reinforcement, long pumping distances, rapid curing for quick return to service and high-build of pipe crowns. Centri-Pipe is not new—AP/M's patented variation called Permacast has been used in manhole rehabilitation since 1985, but the Westlake interceptor was one of the first applications of this magnitude in horizontal pipe.

Using Centri-Pipe technology to apply ConmicShield-treated cementitious grout looked like a good way to overcome the challenges Westlake was facing. Centri-Pipe is a truly trenchless rehabilitation technology, and since the equipment can be introduced to pipe interiors via manholes, excavation is avoided. More importantly, the SpinCaster can be started and stopped at any point in the pipe, and adjusted as needed for changes in diameter. It looked like a perfect way to focus on the interceptor’s problem areas, and realize the savings city officials were looking for.

“We thought it would work, so we put it to bid,” says Kelly. “There were not a lot of contractors who could do this, but we found one and the total costs came in at $1.6 million. We saved at least $1.5 million by avoiding rehabilitation of the undamaged pipe.”

A job done right
Contractors diverted flows around individual trunk line entry points by using 12-inch pumps to move waste overland. The pipe area that was subject to rehabilitation was cleaned and scoured with a high-pressure spin washer to remove loose material. As a final step before applying new grout, Westlake designers requested a ConmicShield rinse of the cleaned interior to be certain MIC could not develop behind the new liner.

After analyzing the interceptor’s interior diameter, water load, extent of damage and other factors, engineers determined that a 1/2-inch liner of PL-8000 grout with ConmicShield would be optimum. This would repair and strengthen the interceptor, and prevent corrosion while preserving flow characteristics.

In all, Westlake rehabilitated just 3,961 lineal feet of the interceptor, as opposed to the 7,200 lineal feet that would have been required by manhole-to-manhole rehabilitation. The work began in 2009 and was completed nearly one year later; this meant that seasonal adjustments had to be made as the work progressed.

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