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Norfolk Replaces 92 Year Old Pipe With Hanson Pressure Pipe
The city of Norfolk, VA, needed to replace 92-year-old reinforced concrete pressure pipe that had reached the end of its useful life in the city of Portsmouth.
The Cage Pipe Replacement Project Phase I, taking water from the reservoir in Suffolk to the 37th Street water treatment plant, was relatively straightforward as it runs parallel to an abandoned railroad. Those long stretches afforded Hanson Pressure Pipe the opportunity to introduce Norfolk to bar-wrapped concrete pressure pipe and the installation efficiencies it provides.
Hanson supplied more than 4,100 feet of 36-inch diameter AWWA B303 bar-wrapped concrete pressure pipe in 32-foot lengths. The technical specifications included a choice of ductile iron pipe or AWWA C303 bar-wrapped concrete steel cylinder pipe. While the use of bar-wrapped concrete pressure pipe is fairly new to this marketplace, bar-wrapped pipe has been in use for more than 60 years in other parts of North America.
Recently, Hanson engineers and field service staff spent a half day with the project owner and consulting engineer presenting technical information showing how bar-wrapped concrete pipe meets the project’s design and quality standards. Hands-on demonstrations from Hanson’s Field Services team, including welding, tapping and repairing the pipe, provided valuable insights for the owner and engineer on the pipe’s capabilities as well as practical tips for installation.
Along with bar-wrapped pipe’s durability, dependability and ease of repair, its availability in laying lengths up to 40 feet means fewer joints versus the pipe being replaced. The pipe also was installed at a somewhat greater depth, four feet, than the existing pipe. The existing soil, being relatively soft, required careful attention to the bedding.
Installation of the new pipe has progressed smoothly, according to the general contractor, with the B303 proving easy to work with and simple to install with no added accessories required for installation. Longer trench boxes are required to accommodate the 32-foot laying lengths. The B303 pipe weighs less, on a unit basis, than prestressed concrete cylinder pipe, which has resulted in cost savings for the installing contractor.
Hanson’s engineering staff has provided helpful education to installers and has been a great resource from project design all the way to delivery.