With thousands of miles of buried water mains providing drinking water to its communities and the wastewater pipelines forcibly moving raw sewage to treatment plants, it is important to maintain operation of these pipelines and build a resilient network of pipelines to accommodate the high demand from our society.
Time and stress on the pipe system causes our infrastructure to naturally deteriorate overtime, albeit at different rates. What we see when looking at population growth and aging infrastructure is two diverging trends that are inevitably bound together. This population growth increases the demand on our pipelines and, in turn, puts additional stress on the existing system. In many areas today, we are putting more stress on a weaker pipe as compared to when that pipeline was installed.
There are many great innovative rehabilitation solutions that the trenchless industry has developed and commercialized over the years. However, each one naturally has its own technical envelope from pressure rating, install lengths, work zone dimensions, installation duration, downtime, etc. However, what happens when an owner has a pipeline that has project parameters that fit with the technical envelope of some solutions but not others in different areas of the project. For example, what if an owner has minimal intermediate access along a long pipe length with multiple bends? What about a pipeline with an unusually high operating and surge condition to consider?
With the trenchless industry being technology-based, there are always advancements to the continual development of innovative solutions to address our aging infrastructure. One major challenge is responding quickly and cost-effectively to recently failed pipelines or a failure is eminent. The country’s sprawling population growth, historical landmarks, environmentally sensitive areas, and wetlands have made it difficult to address these failing pipelines in a timely manner, within a reasonable budget, and with minimal disruption to other infrastructure and the local community using traditional pipe replacement methods. Fortunately, there are innovative solutions that are readily available for addressing these failing pipelines and it is these rehabilitation solutions that are the key to getting pipelines fixed and back in service. The advancement of a flexible fabric reinforced pipe lining system has provided the opportunity to review another “tool in the toolbox” for finding the best fit solution for each scenario.
Flexible Fabric Reinforced Pipe (FFRP) is an important innovative development within the industry to provide a technical envelope that can adapt to more challenging projects when the project requirements such as pressure rating, intermediate access constraints, and schedule all become equally important for the project. When evaluating the applicability of FFRP for a project, it’s paramount to understand what FFRP is providing for the project. Factors such as how the liner interacts with the host pipe, rigidity to internal operating pressures impacting longevity of the liner, and design service life based on testing are critical to the review and application of FFRP to various pressurized pipelines.
There is an array of different emergency repair solutions available when responding to a water main break whether the pipeline is buried, bridge-mounted, or other pipe locations. The failure mode of the pipeline may be different requiring certain types of solutions such as being caused by either failing joints, isolated deterioration, or damage to the pipeline from nearby work. The following two case studies showcase the reasons why FFRP was chosen for each project. Each project had unique situations where there were multiple challenges needing to be tackled and there was an effort to find a solution that could address these challenges equally.
Pressure PipeCase Study #1
A municipality in Missouri had two parallel ductile iron sewer force mains (12- and 18-in. diameter) that had a history of pipe ruptures and failure leading to multiple point repairs needed in an existing concrete pavement roadway. The smaller diameter pipeline serves as the discharge during the dry season and larger in tandem with the smaller diameter, would be capable of full flow capacity during the wet season.
Due to the various operational needs throughout the year, the owner was needing a solution that had the high-pressure rating of the system but not reduce the final internal diameter to negatively impact the flow capacities. Due to the location of the pipeline within the limits of a concrete pavement roadway, reducing intermediate access points through excavation pits would further reduce the total cost and impact of the project.
Since there were parallel pipelines, the project was split up into two separate installations to allow for the other pipe to be used as a bypass while each pipe was shut down for rehabilitation.
Pressure Pipe Case Study #2
Bridges are not only an efficient way of connecting two land masses or span over other major infrastructure features for transport of people and goods but also serves as the main support for pressurized pipelines. When these bridges are built, the proper support features are installed to accommodate different diameter and type of pipelines.
Although this is a great secondary use of a bridge, the mounted and exposed pipeline can create quite a scene when the pipeline has an abrupt failure. Typically, these failures are both seen and heard for those nearby. As a result, a strong sense of urgency is placed on the owner and their team of engineers, contractors, and operators to address the failed pipeline. However, many times these spectacular failures can be avoided when the existing condition of the pipeline is identified by routine inspection.
A municipality in Florida had experienced an unfortunate joint failure on a 1,400-lf long, 12-in. ductile iron water main suspended beneath a bridge. After isolating the main and performing additional inspections, the owner determined that the remaining joints were susceptible to future failure. The owner approached the trenchless industry for innovative feasible solutions.
With the pipeline length at approximately 1,400 lf and mounted underneath to a four-lane bridge, intermediate access along the length and at the ends were extremely limited. There was not much space to mobilize larger equipment or set up a work zone around each pipe end. Combining the requirements for a long installation, pressure rated lining system, and limited work space, there are not many solutions that can meet these parameters. However, FFRP was an excellent application that could address the failure mode of the pipeline and accommodate the tight site constraints.
As our nation’s water and wastewater infrastructure continues to deteriorate and it is important more than ever to continue developing innovative solutions that can keep up with the two diverging trends between the deteriorating infrastructure and population growth. The higher demands on our weakening pipelines results in more frequent failures and constitutes a stronger urgency to address our aging infrastructure.