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Collierville, Tennessee has a quaint downtown district, so when underground sewer pipelines showed signs of weakness, tearing up streets to replace the pipe would have been a civic nightmare.
The trenchless solution designed by consulting engineers Jordan, Jones & Goulding. (JJG) had new seamless cured-in-place-pipe (CIPP) built inside the old pipe. Insituform Technologies (ITI) installed the CIPP using a felt tube saturated with Vipel corrosion-resistant resin from AOC. Adding a dimension of community pride to the project, AOC world headquarters are about five minutes away from the Collierville downtown.
“If this project had been standard open-cut construction, it would have taken six months, instead of the four-and-a-half weeks it took,” said ITI Senior Project Engineer Randy Hansbrough. “By not having to dig trenches, the environment and town ambiance were preserved. Businesses did not have to face shutdowns, and roads stayed open to traffic.”
The Collierville project rehabilitated 12,800 feet (3,900 m) of 8-in (20.3-cm) vitrified clay and concrete sanitary sewer pipe installed at various stages in the 1960s. “This was a major infrastructure management undertaking,” said Murray Beard, Project Manager for the Public Service Department of the Town of Collierville. “There were a variety of issues in different areas. In some places, soil settlement was causing depressions in the roadway. There were leaking joints. Root intrusions were causing backup. And we had inflow/infiltration of storm waters during heavy rains.”
Steve Lindsey, Senior Pipelines Rehabilitation Specialist for the Memphis office of JJG, Inc., developed the plan to fix the problem by having the host pipe cleaned out then relined with Insituform CIPP.
The Insituform process starts with a non-woven polyester felt liner custom-made for the host pipe and in predetermined lengths for on-site insertions. Prior to insertion, the felt is impregnated with wet resin at Insituform’s facility in Jacksonville, Florida, then shipped to the job site under controlled conditions to prevent premature resin cure. To speed installation, minimize disruption and eliminate digging, access to the Collierville sewer pipe was made through existing manholes. As the wet-out tube was inserted, internal water pressure or air pressure was used to invert the tube and move it forward and against the pipe’s inner wall. Depending on the pipe conditions and location for a specific inversion, the water was heated or steam was introduced to raise the temperature of the resin to its curing point. Temperature was then maintained for a specific time to ensure a complete cure. When fully cured, the resin became a crosslinked solid which resulted in a new seamless liner inside the old pipe.
The Vipel resin for the job is a high molecular weight isophthalic polyester engineered for CIPP use and proven in applications throughout North America. Lindsey pointed out the significance of CIPP resin specification. “As important as the felt tube is, it is just the vehicle for getting the resin inside the host pipe,” he said. “The resin is the new pipe.”
ITI Field Engineer Bill Crockett observed, “Collierville shares a common thread with many other small towns we’ve been to across America,” said. “Their sewer infrastructure was aging, and digging up Main Street would be incredibly disruptive.”
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