No shovel required: Upgrading underground pipes

Trenchless technology is being used to extend the life of a pipe with reduced impacts to the community.

April 16, 2018 | By: Jose Salas
Crews lower a 40-foot PVC pipe into a small trench as part of a pipe rehabilitation project on 29th Avenue.

 

In late March and early April, 29th Avenue was partially closed between Sheridan Boulevard and Fenton Street for a rehabilitation project on a 36-inch steel pipe originally installed in the 1920s as one of the final phases of the Ashland Reservoir Tank Replacement project.

This portion of the project was supposed to last about three weeks.

Instead, crews installed 1,200 feet of pipe in just one week, giving the neighborhood and local businesses their streets back more quickly than anticipated. But how?

Crews prep the first section of PVC pipe to be pulled through the existing underground iron pipe.

The answer: Trenchless technology.

For 1,200 of the total 1,900 feet being replaced on the stretch, the crew only needed to expose two sections at the ends of the old pipe instead of having to dig up the entire section of road and dirt to install the new pipe.

This is where the new technology comes into play.

Forty-foot segments of 30-inch PVC are lowered one at a time into one of the openings of the old pipe. Each new section inserted into the pipe goes through special machinery that fuses the ends of the new pipes together before they are pulled through the old pipe.

“While not necessary, a third trench in the middle was also dug for inspection and cleaning of the existing pipe,” said Martin Garcia, senior engineer at Denver Water. “Getting the pipe clean after more than 90 years of corrosion on the inside had built up was important to the success of pulling the PVC pipe through.”

Special machinery thermally fuses two sections of PVC pipe before being pulled through the existing iron pipe.

According to David Wilson, engineering project manager for Denver Water, this method has taken half the amount of time that would have been needed on 29th Avenue if the same length of pipe was replaced the traditional way.

“The goal of this project was to extend the life of the main for up to another 80 to 100 years with an affordable, low maintenance solution,” he said. “Trenchless technologies are a cost effective and efficient way to extend the life of the pipe while reducing construction impacts to the community.”

Although new to Denver Water, this method originated in the oil industry and has now moved to water utilities across the country.

The materials provide significant savings in labor and equipment costs as the pipe is more durable, requires fewer fittings, has greater corrosion resistance and fewer joints — providing a leak-tight seal.

A third trench made in the middle of the project for inspection and cleaning purposes.

And, even though smaller in diameter, there is no loss in water distribution, as its smooth lining allows water to flow through the pipe more easily than in other types of pipe.

So, why doesn’t Denver Water use this material and technology for all pipe upgrade projects?

Because the pipes can’t be pulled around tight corners due to its limited flexibility, these pipes can only be installed in straight sections, said Wilson.

“This is only the second time Denver Water has used this technology,” he said. “But we plan to continue applying it to pipe upgrade projects in the future.

For more information on this technology, visit PlasticPipe.org.

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