Fulton County, Georgia, has a series of reinforced concrete pipe (RCP) line segments near the Chattahoochee River. These lines are located off Riverside Drive in Roswell. Recently, these segments have witnessed infiltration during river overflows due to cracks in the pipeline walls.
The decision was made to fully renew these segments; however, a trenchless technology was necessary because of the project location. The pipes run beneath a suburban area that includes a busy road, the popular Roswell Riverwalk Trail, the large Saint Andrew Catholic Church parking lot and Riverside Park. Digging in this area would cause costly disruptions.
Choosing Spiral Wound Lining
One of the overall goals of Fulton County was to reduce spills while improving the infrastructure. Given these considerations and the project location, a trenchless technology was needed to renew the RCP segments. Spiral wound liners were chosen as the trenchless technology to renew the RCP. Spiral wound utilizes machinery to form PVC liners directly within the existing pipe. The PVC profile is delivered to the jobsite as a continuous strip reeled on a spool. The strip is then fed through the existing access (in this case a manhole) to the winding machine located within the pipeline. The machine locks the edges of the strip to form a continuous liner.
The features of this trenchless method were crucial for the application. First, a structural solution with a limited construction footprint above-ground was needed. Live flow was also to be present in the pipelines during lining. The trenchless technology needed the ability to be installed in various levels of flow.
Kemi Construction Co. of Atlanta, currently operating with Fulton County under a repair and rehabilitation contract, chose spiral wound installer, Ruby-Collins Inc. from Smyrna, Georgia, to perform the rehabilitation work. The two diameters (60- and 42-in.) required different spiral wound methods; SPR and SPRTF/RO. SPR, manufactured by SEKISUI SPR, was utilized to line the 60-in. segments. The SPR liner is wound as a fixed diameter on a guide-frame constructed in the shape of the host pipe, which in this case the RCP segments were circular. This leaves space between the pipe wall and the completed liner. Once the pipe is lined from manhole to manhole, SPR requires the annular space to be grouted.
SPRTF/RO would be used for the 42-in. segment. The SPRTF/RO lining system features different machinery with hydraulically powered arms. These arms line the PVC tightly against the host pipe wall, meaning no annular space grouting is required after a section is complete.
The contractor for the project, Ruby-Collins Inc., witnessed some challenges due to extremely high flow rates, as well as groundwater infiltration from the river after rain events. Although spiral wound liners can be installed in live flow, this typically means up to 30 percent low velocity flow within the pipeline. This is largely due to safety concerns. At the project’s onset, the pipelines were running higher than 30 percent flow at high velocity. This led Ruby-Collins to increase the bypass pumping operations to reduce the flows to a manageable level. Although some delays occurred, lining pressed forward with the flows at a controllable level.
Another challenge was Ruby-Collins’ familiarity with the SPRTF/RO technology. Ruby-Collins has a great deal of experience with SPR. This is owed to their successful installation of more than 10,500 lf of SPR liner a year prior for the City of Atlanta. With some slight variations, the 60-in. liner installation was familiar to the crew.
Both SPR and SPRTF/RO incorporate machines that traverse the pipe while constructing the liner. SPRTF/RO, however, is a different winding machine and process. Instead of winding the SPR liner with a gap between the liner and host pipe, the SPRTF/RO liner is wound directly against the pipeline wall. Another factor is the limited space to work within the 42-in. section. The machinery and process vary enough to where SEKISUI SPR needed to properly train the installer prior to installation.
This training proved challenging with the SPRTF/RO technicians located overseas, and the installation set to occur May 2020; at the height of the COVID-19 pandemic. At this point international travel was banned, requiring the solution to be digital. The SPRTF/RO training sessions resulted in a coordinated digital strategy that included video modules and teleconferencing with spiral wound technicians.
Ruby-Collins completed the 60-in. portion in May 2020, lining more than 1,100 lf of RCP. They immediately transitioned to SPRTF/RO virtual training and prepared to line the 42-in. section. With all the delays and the challenge of virtual training, they were able to successfully line the 400-lf section of 42-in. RCP in June.
“Riverside was an extremely challenging project due to the river being so close and the heavy rainfall we experienced during project. The SPR lining was ideal for this type of project allowing us flexibility with the conditions out of our control and minimize the disturbance to the community around us,” said Ruby-Collins project manager Mike Lawson.
As part of Public Works Week in May 2021, Fulton County celebrated the success of the rehabilitation project with a Project Improvement Ceremony. Speakers at the event noted the success of this project and the overall campaign for reducing spills within the County. The Ceremony included local politicians, as well as representatives from SEKISUI SPR, Ruby-Collins and Fulton County.