Tarrant Regional Water District (TRWD)
A patch of corroded prestressing wires exposed during a verification
Pipe Diameter: 72”, 84” and 90”
Pipe Type: PCP
Distance Inspected: Approx. 1 mile
Service: Remote Field Transformer Coupling (RFTC)
The Tarrant Regional Water District (TRWD) is a raw water supplier that serves ten counties in north central Texas. Most of the 1.5 million people served by the District are in Tarrant County, which includes Fort Worth and surrounding communities. In 2001 the District delivered over 366,000 cubic feet of water to its customers.
Both the Richland and Cedar Creek transmission pipelines are composed of prestressed concrete cylinder pipe (PCCP). Beginning in 1981, nine years after installation, the District began to suffer an increasing number of failures. The District explored corrosion as a possible cause by measuring cell to cell and pipe to soil potentials and found that its pipelines ran through extremely corrosive soil. As a result, TRWD enacted a successful cathodic protection program designed to minimize future corrosion. In addition, TRWD conducted a condition assessment of its pipeline using the Remote Field Transformer Coupling (RFTC) pipeline evaluation system from the Pressure Pipe Inspection Company (PPIC) to determine the integrity of individual pipes.
Through the inspections, the District has been able to identify and replace a number of distressed segments. This has improved the integrity of the pipelines, and TRWD was able to reverse its earlier decision that it would have to replace them. The damage identified by the RFTC system demonstrates that the Richland pipeline has fewer damaged segments than the Cedar Creek line, possibly due to the shorter time period it was in place before adding cathodic protection. Based on the number of pipe segments found with damage great enough to require replacement, the District expects that all major replacements will be completed in a few years – at a fraction of the cost of replacing the entire pipelines.