With much of the world’s water and sanitary sewer infrastructure in the ground for more than 100 years, trenchless technologies in many situations are the only practical or, in some cases, possible solution.
Of those, pipe bursting offers several benefits.
Using the old pipe as a “path,” a winch pulls a bursting tool through the existing pipe, breaking or busting it in the process and simultaneously pulling in a new pipe behind the tool, eliminating most excavation. Ductile slitters are available to replace non-fracturable pipes, such as ductile iron and steel. Frequently, pipe bursting allows upsizing of the pipe being replaced.
An example is a recent project in Grand Prairie, TX, to replace a segment of the city’s CWSRF Waste Water Rehabilitation Project. Contractor No-DigTec installed 550 feet of 18-inch diameter HDPE pipe at a depth of 15 feet through Turner Park, a community sports area.
“Pipe bursting allowed the pipe to be installed without tearing up the parkland or streets running through it,” said John Newell, president of No-DigTec. “The entry pit was next to the road. We went under the street, and the path of the pipe followed a creek and also passed under a storm drain.”
There are two basic methods of pipe bursting: static and pneumatic.
Newell said that for this project, pneumatic bursting was used. This method employs a bursting tool with percussion hammer action to help the expander head break the host pipe. A winch located at ground level maintains constant tension on the bursting head with heavy metal cable.
“There was some concrete encasement under the creek and storm drain that we had to hammer through before we got to a sharp bend radius that followed the creek,” Newell said.
Pipe was laid and fused along the road.
“There was plenty of space for a good job-site layout,” he noted. “In addition to stringing the pipe, there was plenty of room to load the hammer and hoses.”
Two bursts were made, the longest was 350 feet, the shortest was 250 feet. A Hammerhead 20-ton HG20 bursting head and 24-inch expander were used on the longest burst. For the shorter one, a 16-inch Hammerhead tool hammer and 18-inch IPS expander were used.
“The 20-inch hammer might be considered unusual for the project, but we wanted plenty of power,” said Newell. “We wanted to get from point A to point B without any stall outs. After going through the encasement there was a sharp radius before getting to the finish line, so we put more power on the front end to avoid the risk of getting stuck due to pipe drag.”
Power for the tools came from Sullair 900 and 375 cfm compressors providing 1,275 cfm output. Support equipment included a New Holland backhoe, two Takeuchi excavators and a McElroy fusing machine.
Newell said the original contract was for 2,646 feet of bursting, with 550 feet added during the course of construction. Start to finish, the pipe bursting segment took five weeks.
Based in Dallas, TX, No-DigTec is the largest pipe bursting contractor in North Texas. “We are one of a handful of companies in the U.S. with the experience and equipment to burst large-diameter pipes of 24 inches and larger,” he said.
The company also has the capability to construct custom tools to fit specific needs.
“Pipe bursting offers many benefits for addressing rehabilitation of the nation’s water and wastewater infrastructure,” he concluded. “One of the most important is the ability to upsize new pipe, providing greater capacity. We believe pipe bursting will take on an increase of the water and sewer pipe replacement workload.
“Water main replacement is a growing segment for pipe bursting. We are seeing more jobs designed specifically for pipe bursting because it saves the cities money – 85 to 90 percent less excavation, which equals more pipe in the ground for money spent.”
With a population of approximately 175,000, Grand Prairie is one of several cities located between Dallas and Fort Worth.
Grand Prairie serves 47,500 customer accounts and 7,604 fire hydrants. Water production is 25.7 million gallons per day delivered through 893 miles of pipe. There are 872 miles of sewer collection pipes.
FOR MORE INFO:
(800) 331-6653, hammerheadmole.com
(918) 836-8611, mcelroy.com
(717) 355-1121, newholland.com/na
(706) 693-3600, takeuchi-us.com