Slipline rehabilitation with Bagela Pipe renewal winch RW 20
Denver Water turns to Slipline rehabilitation for large-diameter water transmission main
Denver Water has an active pipeline rehabilitation program targeting aged metallic distribution and transmission pipelines with a history of leaks and repairs. For the past few years, Denver Water has been utilizing cement mortar lining (CML) as a preferred rehabilitation technique for existing cast iron and other metallic pipeline infrastructure. A targeted water line is taken out of service, mechanically cleaned and then CML is mechanically coated on the inner surface. Denver Water intended to use this same type of CML rehabilitation as part of the Ashland Project with Conduit No. 1 in the fall of 2017. This 36-inch (914 mm) cast iron transmission line was estimated to be close to 100 years old, installed sometime in the early 1920s.
Due to unanticipated delays in the CML process, Denver Water reached out to Underground Solutions to investigate the possibility of sliplining the existing 36-inch pipeline with a 30-inch Fusible PVC® pipe.
Denver Water verified that a reduced inside diameter from roughly 36-inches to 30-inches (762 mm) would still adequately meet the demands of the network. PVC pressure pipe larger than 24-inches (609,6mm) had never been installed in Denver Water’s system, so this would be a first. The age of the pipe, the need to keep the Ashland project on track and the immediate availability of 30-inch Fusible PVC® pipe helped to fast track approval and a slipline solution was slated for construction. T. Lowell Construction, Inc. had already been awarded other portions of the Ashland project and was the low bidder for the slipline portion, so was awarded the work. T. Lowell has installed Fusible PVC® pipe many times before and requested equipment assistance from TT Technologies, Inc., who recommended a 20-ton winch for the installation of the new Fusible PVC® pipe. Denver Water required T. Lowell to first pull a 40-foot (12 m) ‘proof-piece’ of Fusible PVC® pipe through the entire line for inspection before proceeding with the full installation. The proof-piece passed inspection and verified there were no critical issues with the sliplining process for that segment of pipe
Ashland Conduit No. 1 runs beneath 29th Avenue near Sheridan Boulevard in an extremely busy area of suburban Wheat Ridge. To reduce excavation impacts in the middle of these busy streets, the team opted to use a fuse and pull operation to install the Fusible PVC® pipe.
This eliminated roughly 50 percent of the necessary insertion pit length compared to fully assembling the pipe at-grade and then inserting it. Instead, 40-foot lengths of Fusible PVC® pipe were lowered into the pit and fused at invert-depth. When each joint was completed, the assembled pipe length was pulled 40 feet into the existing cast iron pipe and the process would be repeated.
After the entire 1,215 feet (364 m) of Fusible PVC® pipe was installed, it was pressure tested at 150 psi for two hours. The annular space between the new Fusible PVC® pipe and existing cast iron pipe was grouted with a cellular grout mix and the line was reinstated. At 30-inches, this section of Fusible PVC® pipe is now the largest diameter PVC pressure pipe to be installed in Denver Water’s vast network of potable water distribution and transmission pipelines.