The Importance of Trenchless Technology for Pipe Rehabilitation

Pipe rehabilitation

Many experts agree that that the greatest technological advancement is the last 200 years has been sewer and water infrastructure. A functioning sewer and water system is the foundation of a healthy and prosperous society. Good sanitation leads to good health, which leads to greater productivity and prosperity.

Founded in January 2000, PW Trenchless is a leader in the trenchless underground utilities construction sector in British Columbia, Canada. They were the first to employ pipe bursting in that province.

“The city of Vancouver, British Columbia, with a population of two million or so, is similar in size to many cities in North America. A city that size has approximately 30 billion dollars worth of sewer and water infrastructure. Let’s assume the lifespan for that infrastructure to be 100 years, which a lot of it is, although it varies greatly by product. That means municipalities are replacing 300 million dollars of sewer and water infrastructure each year,” David O’Sullivan, President, PW Trenchless.

Pipe updating and maintenance 

A lot of the sewer and water infrastructure in North America was installed between the 1920s and the 1950s and we are a lot busier now. “Today, there are so many more cars. A two-lane highway back then is six lanes today. You can’t dig up streets and interfere with people’s lives. That’s why trenchless technologies are so important,” says O’Sullivan. “Plus, the act of digging down to replace a utility is a laborious and time-consuming event. To remove a pipe two inches in diameter located three meters (10 feet) below the surface, requires a lot of digging. Plus, to do it safely, you need to dig 1.5 meters (five feet) wide to fit a trench box in there, so you end up removing 4.5 cubic meters of earth to remove only 0.01 cubic meters of pipe.

That calculates to be the removal of 100 units of earth for every one unit of pipe to be removed/replaced. “Plus you have to factor in the cost of trucking out that material and filling the cut,” says O’Sullivan, “And, when these projects require cutting into asphalt, you devalue the value of the asphalt. A road with three cuts loses $500,000 in value; trenchless technology saves municipalities from bearing those costs.”

According to O’Sullivan, one key to minimizing sewer and water maintenance costs is to manage the assets in a similar way to fleet management. “Back in the ‘90s, the WRC (Water Research Center) started getting into asset management, which allows people to proactively manage underground infrastructure. Prior to asset management, there was only reactive management. If something broke, you fixed it. Otherwise, you didn’t touch it. But, asset management allows us to get a better handle of the assets and manage them in a more cost-efficient and less disruptive manner.”

Europe, he says, is wasting 40-percent of their water through cracks and leaks in the pipes, because they never put the money into fixing the problems. And, the southwest US has water shortages and they also lose a significant amount of water through cracks and leaks in their pipes.

Popular trenchless technology types

There are several methods of Trenchless technology:

  • Sliplining - This is one of the oldest trenchless pipe rehabilitation It involves inserting a new, smaller diameter pipe into an existing larger pipe. This method takes less time compared to other trenchless methods and long runs of pipe with minimum connections can be installed. On the downside, in many sliplining projects, manholes don’t provide adequate access to allow for sliplining, so insertion pits are created for each pipeline segment. Although the amount of earth excavated for these pits is less than the amount required by conventional excavate and replace methods, it may still result in disruptions to surface activities.
  • Pipe bursting - Also known as in-line expansion, this method demolishes the existing pipe with the use of a bursting tool that pushes the existing pipe radially outward until it shatters into fragments, while simultaneously pulling the new pipe behind, thereby installing it. This method is preferred when the existing pipe has suffered significant damage. This is one of the fastest trenchless pipe rehabilitation techniques, but it includes two possible negatives: a disruption to the surrounding soil and the need to install temporary rerouting infrastructure as the rehabilitated pipe is taken out of service.
  • Cured-In-Place-Pipe Liner (CIPP) - This is a renewal process that involves inserting a flexible liner filled with a resin into a host pipe—the pre-existing pipe—using a liner inverter. The inverter expands until the liner presses against the outer walls of the existing pipe. When the resin in the liner cures (hardens, in a way similar to concrete), it reinforces the host pipe. Its one drawback is its inability to correct any distortions to the existing pipe.

“Methods of trenchless pipe rehabilitation are like circles in a Venn diagram; they have some commonality but also stand on their own as well,” says O’Sullivan. “The two main criteria for determining which method will work best are suitability and cost-effectiveness.

For instance, CIPP is suitable for sewer lines up to 24 inches (600 mm), although other factors come into play as well. Siplining is good for pipes from 18-30 inches in diameter, so you can see where those two methods overlap and other factors may determine which is the best method for that situation.”

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