The City of West Palm Beach (WPB) makes a concerted effort to engage its citizens.
As one of the three largest cities in South Florida, WPB is a vibrant, growing waterfront community with a population of more than 100,000. Since 1974, WPB has experienced exponential growth in its population and correspondingly, in its wastewater management needs. During this time, WPB has continuously upgraded its pumping and treatment processes based on advances in regulations and technology.
In the evolution of its force main strategy, WPB has undertaken a variety of initiatives to manage its network to reflect the needs of its community. This ties into an overall strategy by dealing with rehabilitation needs proactively to prevent costly system failures while planning the rehabilitation and assessment of an entire system over the long term.
West Palm Beach bucks the trend to replace based on age of system
Historically, management of a force main network has been based on the general age of the system without specific information of the system in relation to its normal and extreme weather operation.
Bucking this trend, WPB takes an enlightened view to the management of its wastewater network, with age of the system not an automatic reason to replace or rehabilitate. While complete replacement would be ideal, the cost associated with full scale replacement is unfeasible. Ratepayers demand fiscal responsibility and are reluctant to sign over blank cheques to their utilities.
As a testament to its proactive stance, WPB has completed the first phase of a condition assessment, design and rehabilitation program of its force main network, which includes a nearly six-mile section of pipeline that conveys wastewater from Lift Station 22 to the East Central Regional Water Reclamation Facility (ECRWRF). Comprised of 42-inch and 48-inch lined cylinder pipe (LCP) and 48-inch embedded cylinder pipe (ECP), this force main, constructed in 1974, is considered the most critical piece of underground infrastructure for the City’s wastewater system.
In 2007, WPB conducted acoustic monitoring of the ECRWRF Force Main to determine what areas were deteriorating, but the results proved inconclusive.
In 2015, with the evolution of condition assessment techniques, WPB retained Pure Technologies to conduct a follow-up inspection using pressure monitoring and non-destructive inline assessment technologies.
For WPB, the process included examination of the ECRWRF pipeline from a wide variety of parameters. For example, manufacturing standards from the original force main design were structurally analyzed in contrast to current design standards.
The program examined current operational and maintenance practices, monitored air release valves and looked at pressure profiles based on the multiple pumping station connections to the force main. By deploying acoustic and electromagnetic technologies from Pure Technologies, WPB identified high priority areas based on gas pockets and structural stress along the force main route. WPB combined this information with rehabilitation and replacement strategies to define the second phase of the management process.
In February, Pure used its SmartBall inspection platform to conduct acoustic leak and gas pocket detection on the line. Unlike traditional external listening tools with limited success on large-diameter pipes, free-flowing SmartBall technology provides a high degree of accuracy, since as the ball rolls, it can inspect every inch of the main to detect leaks and gas pockets.
The SmartBall tool was inserted into the pipeline through a hot tap and acoustic data was collected and recorded as the tool traversed the pipeline, where it was later retrieved at a bypass grit chamber.
Next: PipeDiver electromagnetic inspection
Subsequently, Pure deployed its free-swimming PipeDiver platform to perform an electromagnetic (EM) inspection to locate broken prestressing wire wraps in the LCP/ECP pipe. Unlike more restrictive assessment tools, PipeDiver is a flexible, free-swimming tool that flows with the product and is able to easily navigate through most butterfly valves, apertures and bends in the pipeline, delivering electromagnetic (EM) data for a variety of pipe type and materials.
EM technology provides prestressing wire-break estimates on each individual section of PCCP, which is the best indicator that this type of pipe will fail. This allows for one deteriorated pipe to be identified within an entire pipeline that is in good condition overall, and also provides the baseline condition on all pipes in the inspected distance.
Results guide the success of the program
During the SmartBall inspection, zero (0) leaks were detected, while 23 recordings were indicative of entrained gas and gas slugs. Of the 1,682 pipes inspected by the PipeDiver tool, approximately 10 percent of pipes displayed electromagnetic anomalies consistent with broken prestressing wire wraps.
Overall, the condition assessment found the majority of the pipe to be in good condition. Pressure monitoring identified intermittent pressure surges within the design standards of the force main. However, this effort elevated the City’s awareness of the relationships between pressure management and the structural integrity of the pipeline.
Based on the completed assessment, the City implemented a two-year project delivery timeline for extending the service life of the force main for another 40 to 50 years. The schedule included a comprehensive community outreach program that has residents onboard with the phased-in design and construction approach.