USACE Water Main Rehabilitation Under I-5 in Tacoma, WA
November 6, 2018 by NASTT Staff
Project profile submitted by Insta-Pipe – Trenchless Pipe Repair using the Pull in Place pressure liner “PRIMUS Line”.
Rehabilitation of a 16” cast iron water supply line to Camp Murray Military Base, WA
US Army Corps of Engineers
Engineering and Installation Partner:
Insta-Pipe Inc. Tumwater, WA
Year of Construction:
Type of Construction Measure:
Rehabilitation of a 16-inch cast iron water main near Tacoma, WA
• Delivery of the flexible 18-inch Primus Liner with NSF/ANSI 61 approval
• Delivery of the corresponding end fittings with ANSI flanges (150 lbs) with NSF/ANSI 61 approval
In 2017 Camp Murray Military Base was replacing their water supply system due to age concerns. The majority of the system was renewed with open trench remove and replace, one of the two supply lines to the base was unable to be accessed in this manner. The supply line runs under a railway as well as Interstate 5, the main interstate highway on the west coast, making a trenchless operation the only solution. The engineers had to select from two options for this project: Primus Line, or HDPE lining. Primus Line was ultimately selected to maximize the hydraulic capacity in the line.
The client opted to have our installation partner, Insta-Pipe Inc. renew the water main with the Primus Line® system, a proven solution for the trenchless rehabilitation of pressure pipelines. The three-layer composite liner consists of an NSF/ANSI 61 certified PE inner coating, a Kevlar® core to accommodate the operating pressure, and an abrasion-resistant PE outer layer to protect the Kevlar® core during the installation process. The semi-structural solution is not bonded to the host pipe, can traverse bends of up to 45 degree, and can be inserted in lengths of up to 8,000 ft. in one single pull.
Maximizing hydraulic capacity was top priority on this project, leading to the selection of Primus Line as the rehabilitation method. The host pipe was cast iron with an internal diameter of approximately 16.38 inches, a length of 305 feet, and contained no bends. With the combination of a short run with no bends, the decision was to install a Primus Line® DN 450 MD with a nominal diameter of 18 inch and a nominal design pressure of 232 psi. Since the technology works with an annular space to achieve long insertion lengths and negotiate bends, the liner provides an actual outer diameter of 16.06 inch and inner diameter of 15.59 inch. The system has a straight-line pressure rating of 200 psi and thus capable of accommodating the maximal operating pressure of 60 psi. To complete the system, the medium pressure connectors with an operating pressure of 150 psi were used to guarantee a durable and tensile strong connection. In a first step, the two excavation pits for the installation of the Primus Line® system had to be created and the water main was disconnected from the pipeline network, opened and CCTV inspected. After that, incrustations and debris were removed with pull through metal scrapers, rubber disks and a vac truck to create a free inner diameter, which is required to make sure the liner is not damaged during the installation process. After cleaning the host pipe, the pre-folded and coiled on a transport reel Kevlar® reinforced composite liner was inserted and subsequently the liner was inflated with 7 psi to turn it into a round shape. Finally, the medium pressure termination fittings were installed and a leak test with a test pressure of 150 psi was performed and successfully completed. Concentric reducers were then used to adapt the 18-inch flanges of the Primus Line connectors down to the 16-inch flanges used in the rest of the supply system.