Fixing sewer pipes, without digging a trench

Steam billowed from a manhole on 12th Street in Coeur d’Alene’s Garden District on a recent rainy afternoon, as the Coeur d’Alene Wastewater Department worked to rehabilitate sewer pipelines.

The cured-in-place pipes, or CIPP, are updated without digging trenches. Instead the city contracted with JUB engineering and Insituform to insert a felt liner into the pre-existing pipes, essentially manufacturing a seamless fiberglass pipe onsite. Insituform uses a boiler to fill the existing pipe with steam, activating a chemical resin called styrene within the liner.

“Once fully cured, the lining acts as a new, repaired pipeline,” Mike Becker, city of Coeur d’Alene Utility Project Manager, said.

Jake Vanbibber, the project foreman, said cities use cameras to grade sewer lines every year. When hydrogen sulfide has eaten away at enough of the pipe, the line will receive a low grade and need to be repaired.

Becker estimated that the 24-inch diameter interceptor pipe being rehabilitated on 12th Street from Mullan Avenue to Wallace predates the 1960s.

The sewer water is bypassed while the project is underway. Any lateral connections blocked to do repair work are reinstated within the same day. The installation process takes several hours instead of weeks as with excavation projects, minimizing construction impacts to area residents and businesses.

Vanbibber keeps the steam between 6-8 psi, so it has enough force to push the liner against the wall of the original pipe.

“The steam gets to a certain temperature that makes the lining hard like a cast,” Vanbibber said.

The CIPP process was first implemented in London in the 1970s. In the United States, engineers began using it for residential application the following decade.

As one of the most widely used rehabilitation methods, CIPP has applications in sewer, water, gas, and chemical pipelines ranging in diameter from 2 to 110 inches.

While the CIPP process is largely deemed safe, in 2017 a professor at Purdue University released a report linking exposure to styrene and cancer in humans.

The National Association of Sewer Service Companies refuted the link, citing extensive research and inspection regulations that deemed the chemical safe and appropriate for use in sewer pipelines. An environmental review the following year by Purdue revealed differing installation practices across states, water contamination incidents in 10 states and Canada, and a lack of safety data for existing installation practices.

Becker confirmed the CIPP process is safe using the standardized materials, both for humans and the environment.