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As the City of Aurora, CO races each year to upgrade 20,000 to 30,000 LF of old cast iron water mains in its distribution system, the idea of replacing pipe with less expense and lower impact to residents becomes an ever-more appealing option. Open-cut installation, an often disruptive and time-intensive construction method, had been utilized historically in Aurora to replace these old water lines. As trenchless installation methods have grown in popularity throughout Colorado, Aurora's engineers became intrigued with the potential savings and reduced environmental impact on its residents, ultimately leading them to investigate pipe bursting for Aurora's waterline replacement program. Pipe bursting is accomplished by splitting and expanding the old pipeline in the ground, while simultaneously pulling in a new, fully-restrained pipeline directly through the path of the existing line without disturbing the surface. Compared to open-cut installation, residents experience less interruption to their water service and considerably fewer headaches on their roadways.
Late in the summer of 2011, Aurora Senior Water Project Manager Joe Kleiner decided to specify pipe bursting for Aurora's waterline replacement project. To maintain competition, Kleiner allowed multiple restrained joint PVC pipe products in the project specifications, including thermally butt-fused Fusible PVC® pipe. BT Construction, which owns and operates a TT Technologies Grundoburst® 800G static burst machine, was selected for the water line pipe bursting replacement project. BT Construction initially opted to use a mechanically-restrained PVC pipe product rather than Fusible PVC® pipe for bursting operations.
BT Construction broke ground a few months following the bid. After preparing the project site, BT began the static-pull, pipe bursting operation. Site preparation included the following:
After pushing the burst rods through the old cast iron pipeline from the receiving pit to the pipe entrance pit, BT was ready to commence bursting. Within minutes of initiating the pull-back operation problems were encountered. The "as-built" construction plans for the old line had failed to identify multiple repair harnesses that had been installed over the years. When the cutting tool and expander head reached the first of many repair harnesses, the hydraulic static burst machine built up a high pull force before finally breaking through the repair harnesses. The rapid release of hydraulic thrust caused problems with the mechanically joined PVC pipe string. BT Construction consulted with TT Technologies and the pipe manufacturer in attempt to resolve the issues. Together, they attempted multiple equipment configurations without success.
After consulting with Underground Solutions' local Construction Manager, the decision was made to switch pipe products to Fusible PVC® pipe. Following the switch to a thermally-fused PVC pipe, 12,000 LF of 8" DR14 Fusible C-900® pipe was installed without incident. Kleiner commented, "Fusible PVC® pipe solved our problems; it is a great product. When we decide to utilize pipe bursting again, we'll do it with Fusible PVC® pipe."
|Pipeline Details and Project Summary|
|Project:||2011 Pipe Burst Rehabilitation, Aurora, CO|
|Pipe Size:||8" DR14|
|Pressure Test:||150 psi|
|Owner/Engineer:||Joe Kleiner, City of Aurora Senior Water Project Manager|
|Contractor:||Mario Moreno, BT Construction|