Miami Beach Assesses Transmission Main Inline Technologies

Critical to its economic success is a reliable supply of water, which is supplied by Miami-Dade Water and Sewer Department through four major transmission mains operated by the City of Miami Beach’s Public Works Department that range in diameter from 20- to 36-inches.

A failure or disruption on one of these transmission mains would significantly reduce Miami Beach’s treated water capacity, and therefore its ability to act as a major tourism destination.

With infrastructure across the United States aging and reaching the end of its design life, utilities are experiencing more pipe failures that are both costly to repair and disruptive to local economies.

Although Miami Beach has never experienced a large-diameter water transmission main failure, it is proactively addressing deterioration on its critical pipelines using condition assessment.

In September 2013, Miami Beach completed an electromagnetic (EM) structural evaluation on 3.4 miles of its largest transmission main – the Julia Tuttle Causeway – which is made up of 36-inch Prestressed Concrete Cylinder Pipe (PCCP), Cast Iron (CI) and High Density Polyethylene (HDPE) pipe.

After completing a prescreening survey, Miami Beach completed an EM condition assessment survey using PipeDiver®, a free-swimming EM tool used to identify and quantify wire breaks in PCCP.

During an inspection, the tool collects a magnetic signature reading as it traverses the pipeline and identifies anomalies produced by wire breaks in PCCP. The tool is ideal for performing a baseline inspection of a PCCP pipeline that cannot be removed from service. The 3.4 mile inspection was completed successfully, with the tool tracked throughout the planned distance.

Staff with PipeDiver tool

The PipeDiver tool identifies and locates wire breaks in PCCP.

Tool insertion

The tool is inserted into a live pipeline in Miami Beach.

In PCCP, the prestressing wires are the main structural component; when wire breaks are found on a specific pipe section, it represents deterioration of its structural integrity. The ability to locate and quantify the amount of wire breaks in each pipe section allows a utility to make rehabilitation decisions and provides a baseline structural condition.

The data collected identified areas of prestressed wire breakage of varying degrees of criticality. The City is currently considering recommendations for rehabilitation, replacement and inspection of the remaining three transmission mains.

By managing its critical pipelines using a risk-based condition assessment approach, Miami Beach is proactively addressing deterioration in order to continue providing reliable service to a major economic hub.


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