Pipe bursting effective in sandy soil, high water table

Problem: The city of Seymour, Indiana, lies about 10 feet lower than the land around it. Therefore, any work at depths greater than 5 feet generally requires a week of dewatering prior to breaking ground. Yet even dewatered, excavating in close proximity to building foundations is risky. When a blockage occurred in one neighborhood’s 16-inch asbestos-cement gravity sewer main, the city called Lawyer Excavation for the repair. 

Solution: For this job, HammerHead Trenchless specified an HB125 static pipe bursting system, designed for use in pipe diameters 6 to 20 inches with 125-ton pullback capacity. It includes a downhole pulling unit and 4,500-psi hydraulic powerpack. Dewatering continued steadily for one week before the burst. Lawyer Excavation then fused up the 560-foot length of HDPE pipe on the surface two days in advance. The crew pulled the pipe into position, fusing it to the pipe puller on the bursting assembly. Ahead of the fuse-on puller was the expander, which would cut the pipe open and expand the pipe path about 25 percent larger than the 14-inch DIPS HDPE replacement pipe’s O.D., reducing friction. The pipe pilot and swivel connection completed the bursting assembly. The HB125 pressure gauge read 90 tons as the expander engaged the old pipe, then subsided to approximately 50 for most of the burst. At times, all 125 tons of pullback capacity was briefly called upon. 

Result: Lawyer Excavation completed the run in just three hours. 800-331-6653; www.hammerheadtrenchless.com.