Old Problem, New Solution
Downtime and disruption are two problems that can wreck business profitability and production. Few things create more downtime and disruption than infrastructure repair.
Gaz Metro, the private gas utility in the province of Quebec, is like any other urban utility company—very busy. The company has thousands of customers and is constantly responding to service calls. Anything that delays or disrupts its fleet of service vehicles is not just an enormous inconvenience, it has a direct impact on public safety, customer satisfaction, efficiency and profitability.
For three years, the company pondered a potentially expensive and disruptive repair project involving 853 ft of leaky 8-in. diameter water line. The pipeline, which fed a fire sprinkler system at their Montreal central facility, was buried beneath a parking lot where Gaz Metro service vehicles are parked. Digging up the line for repairs would have created significant logistical problems and taken more than one month to complete, so the company chose to delay repairs and ignore the puddles of water that seeped to the surface.
“Excavating 800 ft of line across our parking lot would have paralyzed our mobile operations,” explained Samir Tannous of Gaz Metro. It was obvious to Gaz Metro officials that they needed a faster, more cost-effective, less disruptive solution, but until recently, there were no suitable trenchless methods for structural repair of potable water lines. Fortunately, a new technology is now available to solve such problems. For Gaz Metro, it was the solution they had been waiting on for three years.
New technology for water lines
Last winter, Gaz Metro engineers were working on a gas line repair project and called in the contractor, Aqua Rehab, a trenchless pipe rehabilitation specialist based in the Montreal area. During the discussions of the pipe repair, Aqua Rehab noted that it now has a technology for structural repairing of potable water lines, the Nordipipe. This development immediately got Gaz Metro’s attention.
“Aqua Rehab had actually bid on a dig-and-replace repair of the water line three years ago,” Tannous said. “This time, it had a new trenchless technology for structural repair on potable water lines. We are very familiar with this company because we have worked with them before, so we were confident that it could do a good job on the sprinkler line.”
According to Georges Dorval, president of Aqua Rehab, over the past three years, his company has done more than 35 jobs totaling an estimated 125,000 ft with Cured-In-Place-Pipe (CIPP) structural lining of water mains, ranging from 6 to 30 in. in diameter.
For potable water lines, Aqua Rehab is a licensed installer of the Norditube trenchless pipe reconstruction method. Developed by Norditube, the Nordipipe is a patented glass fiber composite multipurpose system that can be used to rehabilitate fully deteriorated pressure pipes. It offers internal and external pressure resistance and is available for diameters ranging from 5 to 48 in. and lengths up to 1,640 ft. It also can negotiate bends up to 45 degrees. Perhaps most importantly, it was granted approval for potable water by the “Bureau de normalisation du Quebec” (BNQ) in 2004. The BNQ establishes standards for potable water and other services based on NSF principles and is accredited by the Standards Council of Canada.
The prospect of getting the water line repaired without major excavation was especially attractive to Gaz Metro. By using the technology, Aqua Rehab needs few access pits, which are typically only 6.5 by 10 ft.
Another important benefit of Nordipipe reconstruction is cost savings. Eliminating extensive excavation and pavement repair cuts the cost of the project significantly.
“In many cases, we can do a trenchless reconstruction for about 50% of the cost of an open cut repair,” Dorval explained. “Much of the savings comes from the fact that our method requires very little digging to install and little or no street repair after the job is complete.”
As with other trenchless technologies, Aqua Rehab uses remote-controlled robotic devices to inspect the pipe before installation and identify lateral connections. The connections are plugged robotically, and after the repair is completed, robotic cutters reopen the laterals.
After an initial analysis of the existing line and the job site, the first step in the installation process is to bypass the damaged line to maintain water service. Once the bypass line is tested, it is filled with water so there is no loss of service.
After the bypass is up and running, Aqua Rehab closes the main valves and digs the access pits. Dorval said it usually requires about three to five days to prepare everything for the actual “reversion” of the Nordipipe liner.
“You have to dig, cut the pipe, clean the pipe, inspect the pipe and plug the service laterals,” he said.
While site preparation is underway, the liner is being prepared at the company’s facility. The glass fiber reinforced woven tube material is first “wet out” with epoxy resin.
According to Dorval, an important property of the resin formula is very low shrinkage.
“You can accept 2 to 3% shrinkage you see in a sewer line,” Dorval said, “but in a water main, you cannot accept any shrinkage. You have to minimize the shrinkage to about 0.2%.”
Dorval also said the epoxy adheres to the pipe, which is especially useful in sealing the service laterals. The resin and lateral service plugs used in the Nordipipe system are designed so that during the curing process, the resin and plugs form a seal between the line and the lateral that prevents leaks.
Once the Nordipipe is thoroughly saturated with epoxy resin, it is loaded into a pressure vessel called a Phoenix reversion vessel, which is carried to the job site in a truck. The truck also has a boiler and power generator that produce steam used to cure the epoxy within the liner.
At the job site, the inversion truck is backed into place adjacent to the upstream access pit, Station A. Once on site, about one-half hour is needed to get everything ready for the actual reversion. The end of the Nordipipe is covered with a poly bag to catch excess resin when the tube emerges at the downstream end, Station B. The tube is then inserted into the host water line. Air is pumped into the tube, which inverts it and deploys it through the damaged line. If a problem should occur during the inversion, or if something should obstruct the tube’s pathway, the Nordipipe can easily be deflated and removed.
The Nordipipe tube deploys through the line at about 5 to 8 ft per minute. The reversion speed is controlled by the electronic speed control of the mechanical powered gearbox.
When the tube emerges at the receiving pit, Station B, the actual curing process can begin. At Station B, bleeder syringes are inserted into the still inflated Nordipipe. Back at Station A, steam is introduced into the line. The bleeders at Station B help pull the steam throughout the entire length of the tube, curing the thermosetting resin. As the resin hardens, it adheres to the host pipe walls and seals the lateral connections to the new pipe.
According to Dorval, the speed of the curing process depends on the type of resin used for the job. In the case of the Gaz Metro project, it took about 30 minutes.
After the new pipe has hardened sufficiently, pressure tests are conducted to ensure that the pipe has no leaks and is ready for use. Connections are refitted, and the access pits are refilled. The entire Gaz Metro sprinkler line project was completed in just two weeks with minimal disruption to the parking lot area. In fact, Gaz Metro service operations were unimpeded during the reconstruction project.
One intriguing aspect of the Gaz Metro job is the implications it has for other potable water line reconstruction projects in Canada. Most North American cities have aging water lines, anywhere from 40 to 80 or more years old. Many of them have developed leaks or have structural issues. Sinkholes and cave-ins associated with water lines are not uncommon.
“Many cities have water infrastructure that has gone way over its normal life cycle,” said Dorval. “Structural, trenchless lining of water mains has come at just the right time.”
The Canadian government has recognized the need to address potable water lines. Canada’s parliament recently approved legislation that will provide 50% of the funding needed to address cities’ infrastructure degradation including potable water line reconstruction.
Municipal waterworks engineers are already looking at possible repair methods for their leaky lines. Do trenchless methods really work?
“Based on what we have seen, the technology worked perfectly,” Tannous said. “If we ever have other water line problems, I would not hesitate to consider the same process again.”
Steve Gibbs is a freelance writer in Memphis, Tenn., who has covered the municipal water and wastewater industry for 15 years. He can be reached at 901/753-3405 or by e-mail at [email protected].
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