Vermont Wholesale Water Supplier Takes Proactive Approach to Manage High-Value Metallic Transmission Mains
When evidence of corrosion-related breaks was revealed in nearby distribution mains, Champlain (Vermont) Water District (CWD) became concerned that a critical metallic water main in its system could be next. To avoid any potential breaks, and the economic, social and environmental costs associated with a failure, CWD jumped into action.
By taking a proactive approach to understand the true condition on a section of this high-value ductile iron (DIP) transmission main, CWD avoided unnecessary replacement work and was able to direct funds where they are truly needed.
CWD is an award-winning regional municipal organization that supplies drinking water to 12 municipal water systems in Vermont. As the largest water supplier in the state, CWD serves approximately 75,000 residential, commercial and industrial users. CWD draws water from Lake Champlain, and three high value water transmission mains supply water to the user municipalities. The year 1972 saw the completion of multiple transmission main projects to link all members of the newly created Champlain Water District, which has 54 miles of transmission mains constructed of ductile iron, with the majority running at 24 in.
Although CWD is a relatively small consolidated water district, they are a leader in their state, nationally recognized for water quality and asset management. As a wholesale water supplier, CWD demands continuity of supply, with no disruptive surprises to service.
After conducting their own risk-prioritization plan, CWD chief engineer Joe Duncan and his team kept with the proactive mindset and began a transmission main asset management program.
While the transmission system is relatively “young” and had no real break history, visual feedback from crews showed distribution mains in the vicinity of the transmission mains were experiencing corrosion-related breaks and in some instances looking like “Swiss cheese.” Due to the high importance of the transmission pipeline, CWD wanted to understand its condition and forestall potential corrosion issues.
In October 2017, CWD engaged Xylem to perform a condition assessment of a portion (1.8 miles) of the 24-in. diameter ductile iron HS-1 Transmission Main. CWD worked with Xylem to take a Pipeline Screening approach — a method of collecting end-to-end data on the pipe that would allow them to make progressive decisions and reduce risk in their system. The scope of work included a high-resolution inline leak and air pocket inspection, transient pressure monitoring (TPM) and a structural design check to ensure the pipe’s design was sufficient for current operational conditions.
For 29 days, sensors were used to record the operational pressures and surges of the assessment portion of the pipeline. Transient pressure monitoring is a non-invasive and cost-effective way to monitor water networks for the presence of damaging pressure surges. By monitoring pressure transients and the source of these events, CWD could identify operational practices that were adding stress to their pipelines. This early warning helps manage damaging pressure variations and mitigate the risks associated with premature pipe failure, prolonging the effective life of infrastructure assets.
Xylem’s innovative SmartBall technology platform identifies leaks and gas pockets in transmission pipelines while the line remains in service, minimizing disruption. The SmartBall tool was recommended for its acoustic sensitivity to small leaks, minimal pipeline modifications required for insertion and extraction and its ability to inspect long distances in a single deployment.
As part of the condition assessment, Xylem also conducted a structural design check to determine if the 1972 pipeline was up to the latest AWWA pipeline standards and could comply with today’s loading conditions.
The SmartBall inspection found no leaks or gas pockets, which was good news for Duncan and an indication that their pipeline was in better condition than expected. Additionally, results from the monitoring and design check further backed this finding, showing that the pipeline was designed for loading conditions greater than the pipeline was experiencing. The pressure monitoring did detect some minor surges that CWD was able to reduce through operational improvements, prolonging the life of the pipeline.
An additional benefit from the SmartBall inspection was that pipeline mapping data revealed that CWD needed to adjust their GIS alignment between two stations to reflect sweeping bends instead of sharp elbows.
“The SmartBall effort gave us peace of mind that one of our original mains appears to be in good condition and we can now focus on other potential areas of concern in an effort to prioritize long term rehab and replacement needs,” said Duncan.
The results gave CWD the confidence that this transmission main didn’t need further attention, and that funds originally earmarked for pipeline repairs could be re-allocated toward other capital improvement projects including valve replacement projects and redundancy work. This proactive water supplier successfully deployed efforts to improve the reliability of services to its customers and as a result, was able to more effectively use their capital across their network.