League City, Texas
Gulf Coast Water Authority (GCWA)
6,800 feet of 39” PCCP water transmission main replaced with CompressionFit™
The Gulf Coast Water Authority (GCWA) and the City of League City, Texas, were faced with the need to rehabilitate 6,800 ft of a 39-in. PCCP water transmission main along a relatively narrow section of roadway. The decision to complete the rehabilitation of this main — which provides an interconnect between the City of Houston and Galveston County — using CompressionFit™ allowed planners to keep the same hydraulic model/capacity, as well as giving the pipe a full structural overhaul that extended the life expectancy to at least 100 years.
According to project officials, the Calder Road project also resulted in a few firsts in North America: 1) it is the largest diameter, high-pressure, full structural pressure pipeline rehabilitation project completed and 2) no other trenchless method has ever completed a project requiring a fully structural solution at an operating pressure of 125 psi. In 2014, Trenchless Technology recognize the project as the 2014 Trenchless Technology Project of the Year.
CompressionFit™ technology uses a high-density polyethylene (HDPE) liner with an outside diameter larger than the inside diameter of the existing pipe to be renewed. The liner is pulled through a single reduction die before entering the host pipe, temporarily reducing the liner’s diameter and allowing insertion. Once insertion is completed, the liner reverts to its original size, expanding until it is stopped by the inside diameter of the pipe and giving it a “tight fit lining” rehabilitation. Due to the tight fit, thin-walled HDPE liners and semi-structural HDPE pipe can be installed.
In the case of the 39-in. PCCP, the existing pipe required a fully structural rehabilitation. The use of CompressionFit™ allowed MPC to install a fully structural HDPE PE4710 DR 17 pipe with a working pressure rating of 125 psi.
The north end of the project was extended by about 300 ft to an existing 36-in. diameter butterfly valve; the south end required a flanged reducer, butterfly valve and blow off. Thrust restraints were needed at both ends of the project to protect the existing pipe from potentially blowing out from the pressure during construction. During construction, the existing water plant was kept connected to the City of Houston water supply or the GCWA water supply through a 12-in. diameter bypass set up aboveground.
The MPC crews worked closely with the community to minimize the disruption during construction, keeping residents informed each step of the way. “Most people when they are kept informed are understanding,” Andy Mayer, President of Murphy Pipeline Contractors, says, noting the City “did a great job prior to the project of informing its residents.”