Pipe Bursting Solves Environmental Issues

July 2012, Vol. 67, No. 7

The city of Pewaukee, WI, recently upgraded its water supply system by spending $1.5 million to install 9,000 feet of 12-inch PVC water main. The city has two water systems, an East Side System and a West Side System.

“We wanted to combine the two systems to serve our customer base better,” says Jane Mueller, Pewaukee’s utility superintendent. “We wanted the reliability of the 12-inch main.”

To make the connection between the two systems, an 875-foot stretch of pipe consisting of both eight-inch PVC and 10-inch HDPE passed through wetlands. The city sought to expand that connection to 12-inch HDPE, but the wetlands presented a challenge. They are regulated by the Wisconsin Department of Natural Resources, which prohibits open-cut trenching in wetlands. Plus, the area is home to two endangered species of wildlife, a Butler garter snake and a rare species of frog.

The city’s answer: the trenchless pipe bursting process. Pipe bursting permitted the 875-foot run to be upgraded to 12-inch HDPE with only minimal surface disruption. “And just from the regulatory aspect, I think it was well worth the cost,” says Mueller.

In fact, pipe bursting for the 875-foot run cost $120 per lineal foot. Open-cut trenching also would have cost $120 per foot, but the pipe bursting avoided any expense for pavement restoration. A two-lane county road passed through the area, and an open trench would have required spending $12 per foot to restore the road.

“So the total cost per lineal foot would have been $132 for open cut,” says Ken Ward, project manager with the engineering firm of Ruekert & Mielke Inc., Waukesha, WI. “Pipe bursting saved us about $11,000, because they would have had to cut into the road with an open trench.”

Class C burst
To burst 875-feet of eight-inch and 10-inch pipe and upsize to 12-inch HDPE definitely ranks as a Class C pipe bursting project, according to the specifications of the International Pipe Bursting Association. Much of the run involved two upsizes.

The pipe bursting process uses a bursting tool or cutting head that is inserted into the pipe being replaced. A rod string is pushed through the run of pipe, and it is used to pull back the tool or cutting head, which shatters or splits the old pipe. An expander behind the head displaces fragments or pieces of pipe as the new pipe is pulled in behind it. Two types of bursting systems are available: pneumatic systems that use the percussive action of a hammer with a bursting head to crack the pipe – and static systems that use brute pulling force to pull back a cutting head and expander.