The City of Lansing, Mich., and its local water utility faced a major challenge in replacing a defective water main.
The 12-inch ductile iron main was prone to breaks at the bottom of a hilly section of Martin Luther King Blvd. The mainline served a growing area of the city, now home to nearly a half- million residents. Residential basements in the immediate area had flooded several times during main breaks, and the prospect of digging and replacing the pipe — with resulting disruptions to traffic — was daunting.
Facing mounting budget pressures, William Erskine, a mechanical engineer with the Lansing Board of Water and Light, supported the use of high-density polyethylene (HDPE) pipe and trenchless installation to fix the line. This would avoid traffic gridlock and save the city hundreds of thousands of dollars in restoration costs.
Troy Freed of Midwest Trenchless Services in Grant, Mich., a utility contractor, used pipe bursting to install nearly 1,600 linear feet of 14-inch HDPE pipe. It was the first time in Lansing’s history that both HDPE pipe and pipe bursting were used.
Challenging conditions
Pipe bursting, which can be pneumatic, hydraulic expansion or static pull, fractures a pipe and displaces the fragments outward while a new pipe, of equal or greater diameter, is drawn in behind.
“This is an area with corrosive, hot soils,” says Freed. “We needed a pipe that could handle this environment and still provide a comparable service life. HDPE pipe, with its resistance to corrosive soils, offered the best option.
“We also were very sensitive to the traffic conditions in this densely populated part of the city. With an open-cut pipe installation, the city was concerned about the significant disruption and anxiety it would cause. The pipe-bursting method gave us a more efficient installation with less surrounding disruption.” The affected section of the boulevard had been widened to accommodate the growth.
What Freed and his contractors found beneath the surface was a damaged 12-inch water main, and a 6-inch parallel line on the other side of the road that had smaller service lines connected to it. That meant that the 12-inch line could be replaced without any water service interruptions. The road is bordered on each side by single-family housing and a schoolyard, so continued service was very important.
Making the pull
Freed’s team of installers spent the first day digging three pits in the middle of the road surface, each 8-by-20 feet. The north and south pits were 1,600 feet apart, and the middle one was dug at a 35-degree curve in the roadway.
The plan was to perform two separate pulls and fuse the pipe in the middle, on the curve. “It could have been accomplished in one pull, but with the curve, it was safer to split the project into two pulls,” Erskine says.
While the pits were being dug, 40-foot sections of HDPE pipe was being fused together on the site. Butt fusion was accomplished by clamping two pipe pieces into a No. 618 fusion machine from McElroy Manufacturing Inc. of Tulsa, Okla., facing the pipe ends to remove contamination, and bringing the ends perpendicular to the pipe axis.
The ends are then heated with a resistance heater according to the pipe manufacturer’s recommendations. When the proper heat was established, the heater was removed, and a fusion force was applied between the pipe ends. This force was held until the joints cooled. The resulting joints were at least as strong as the pipe itself.
On the second day, an HB125 machine from Earth Tool Co. LLC of Oconomowoc, Wis., was set at the middle pit. The crew pulled a section of fused piping from the north pit to the middle pit. The bursting head was outfitted with a cutter/slitter device that split the ductile iron pipe before the head pushes the pipe apart.
Then the machine was re-positioned to the south pit, and the process was repeated to the south end of the line. The final step was to fuse the pipe in the middle and make the connections on both ends.
Planning for success
Proper planning and design of a pipe-bursting project is essential to success, Erskine observes. “You have to know the soil conditions and the condition of the existing pipeline,” he says. “You also have to know if there is close proximity to other service lines. A thorough knowledge of what’s already there is a must.”
Freed knew that pipe bursting has limitations. For example, when used to upsize pipe, it can create ground displacements. Although the displacements tend to be localized and dissipate rapidly away from the bursting operation, Freed knew the possibility had to be addressed on Martin Luther King Blvd.
“The biggest challenge was some heaving in the road surface as a result of increasing the pipe size,” Erskine said. “That did happen in a few spots. But we were planning for that, and knew we’d just have to mill that area. You just need a plan for that onsite and in the budget.”
Seeing results
Erskine estimates that the pipe-bursting project was completed in about 60 percent of the time it would have taken with traditional excavating. The resulting re-paving required just two inches of asphalt instead of 10 inches of concrete and four inches of asphalt, because there was almost no ground disruption.
The final price tag was about one-third that of open cut excavating using another pipe material. “When you’re talking about a project like this, the dollars saved quickly reach the tens of thousands,” Erskine says. “It was something to see. I was impressed with how easily they opened up the hole and how easily the pipe was pulled through. We haven’t had any trouble or calls since the job has been complete.
“It’s refreshing to find not only economical alternatives, but also ones that make life easier for our citizens when aging pipelines have to be replaced. Let’s face it, nobody wants to have their streets torn up for days and even weeks, much less have to pay for that level of frustration. I’m sure we’ll be considering this method in the future.”
Freed, who works almost exclusively with HDPE pipe, observes, “It was about the city’s being willing to take that first leap. Pipe bursting was new to the community, but most people who see it done say they’ll do it this way again.”
Bruce Kuffer, P.E., is manager of polyethylene market development with the Plastics Pipe Institute, based in East Lansing, Mich. He can be reached at 469/499-1054 or bkuffer@plasticpipe.org.
