Working Through Challenges, Clay Pipebursting Project Exceeds Expectations

By Jeff Griffin, Senior Editor | July 2009 Vol. 64 No. 7

"This is highly beneficial in high traffic urban settings as long strings of welded pipe would have inhibited traffic flow and driveway access before and during the bursting operation," he said. "As a result, traffic was not impacted as much during the pipebursting operation."

Kiewit Western was the contractor for this phase of the work with a GMP (guaranteed maximum price) of $5.3 million.

All existing utilities in the pipe zone were identified and marked on plans including fiber optics conduits and electric duct banks which were potholed and surveyed, waterlines, telephone conduits, natural gas lines, storm drain connectors and sewer lines. Potholing of electrical utilities was performed during design. In addition to potholing, soil borings were collected every 150 to 200 feet along the pipe's route.

"Soil boring data is very important for pipe bursting and bore and jack projects to determine feasibility," Haas said. "Soil classification, size and density are of particular importance."

Before pipebursting could begin, two 12 inch HDPE bypass lines – one strictly a backup – were constructed to carry sewage flow during construction. When driveways were encountered, the bypass pipe was trenched under and paved over to allow property owners to have full access at all times. Existing pipe was cleaned and inspected by closed circuit television (CCTV) to ensure there were no severe alignment problems or sags. Also, CCTV was used to locate all existing service laterals which were intercepted, monitored during the operation, and connected into the sewer bypass system which ran adjacent to the pipe being burst.

VCP

Based on previous experience with a number of pipe line materials, the city of Phoenix preferred the use of VCP, Haas said. The Mission Clay No Dig jacking pipe used on the project uses resilient gasket material and stainless steel collars at each low profile compression joint to provide a leak free system. A chipboard compression ring distributes jacking forces from one section of pipe to the next.

Haas said because of the strain on the pipe joint during the installation process, the decision was made to use a double fin elastomer gasket with a five inch width, 13 gauge (0.09) inch stainless steel collar over the standard for 18-inch pipe which utilizes single fin elastomer gasket coupled by a 4½ inch width, 16 gauge (0.06 inch) stainless steel collar.

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