Louisville Water Company Proactively Manages Aging Water Infrastructure
About half of LWC’s 200 miles of large-diameter transmission mains are made of Prestressed Concrete Cylinder Pipe (PCCP). As PCCP ages, the prestressing wires, which make up the main structural component, begin to break due to a number of factors.
The presence of broken wires in PCCP is the main indication that the pipe will eventually fail. Unlike metallic pipe materials that typically fail after a long period of leakage, PCCP is prone to sudden failures when too many wires break in one area. The diagram below demonstates how PCCP typically fails.
Louisville Water completes annual rehabilitation of its large-diameter transmission mains.
(Source: MSW Magazine)
In 2009, LWC experienced a large-diameter PCCP failure. Fortunately for LWC, it was in a relatively low-risk location which reduced its repair cost. The pipeline also had redundancy that prevented a long service disruption.
“Had it broken 2,000 feet down the line, the cost of that would probably have been $10 million,” said Keith Coombs, manager of infrastructure planning for Louisville Water in an article for Municipal Sewer and Water. “We considered ourselves very fortunate.”
After narrowly escaping an expensive pipe failure, LWC began a proactive annual condition assessment program that addresses deterioration in PCCP.
For structural assessment, LWC uses PipeDiver® technology, which is a free-swimming electromagnetic (EM) tool used to identify and quantify wire breaks in PCCP. The EM sensor collects a magnetic signature reading as the tool traverses the pipeline and identifies anomalies produced by wire breaks in PCCP. The tool operates while the pipeline remains in service, allowing LWC to avoid shutting down service to assess the condition of its most critical pipelines.
LWC inspects about 8 to 10 miles of PCCP annually. Typically, between 2 and 4 percent of LWC’s PCCP is found to have deterioration, while less than 1 percent needs to be addressed immediately. This is consistent with industry averages, meaning it is most cost-effective to complete condition assessment and address isolated problems before replacing large sections of pipe, which carries a huge cost.
Pure Technologies’ data from over 8,000 miles of pressure pipe condition assessment indicates that only a small percentage of pipes (less than 5 percent) are in need of repair and therefore have a significant remaining useful life. Condition assessment data also suggests that pipe distress is localized and a significant ROI can be achieved by locating and addressing isolated problems through structural inspection.
Pure Technologies is helping utilities manage their buried infrastructure through its Assess & Address which can often be implemented for only a fraction of the capital replacement cost.
Specifically designed for structural assessment of Prestressed Concrete Cylinder Pipe (PCCP) lines that are live or can’t be taken out of service due to a lack of redundancy or operational constraints.