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Case Study

Trinity River Authority (TRA) – Texas, USA

The Trinity River Authority of Texas (TRA) owns and operates 8.5 miles of 30-inch BWP and PCCP that supplies raw water from Lake Arlington to the Tarrant County Water Supply Project Water Treatment Plant in Euless, Texas.

The 30-inch pipeline, in conjunction with a parallel 54-inch pipeline, conveys raw water to the Authority’s 87 mgd WTP. Treated water produced at the WTP is supplied to five cities in the mid-cities region between Dallas and Fort Worth including Bedford, Colleyville, Euless, Grapevine and North Richland Hills.

Project Details

SmartBall® Leak Detection
PipeDiver® Condition Assessment
Transient Pressure Monitoring
C303 Bar-Wrapped Pipe structural performance curves
November 2012 – July 2013
Pipe Material
Bar-Wrapped Pipe and PCCP
Inspection Length
8.5 miles (14 km)
30-inch (750mm)
Transmission Type
Raw Water

Project Highlights

SmartBall survey identified 4 leaks and 3 air pockets

Only 1% of BWP sections identified as distressed

TRA verified and repaired 3 high-risk BWP sections

Cost was roughly 4% of the replacement estimate of $25 million


TRA had originally planned to replace this pipe­line, but chose to assess and selectively rehabili­tate the pipeline by finding solutions that could identify the most distressed areas. The pipeline spans about 8.5 miles and is made up primari­ly of BWP, although there are some sections of PCCP. It was constructed in 1973.


In November 2012, TRA began a condition assessment program that included transient pressure monitoring, acoustic leak and gas pocket detection, internal electromagnetic inspection, and structural condition assessment including finite element analysis.

For the leak and air pocket assessment, TRA used SmartBall® technology. The SmartBall inspection tool is a non-destructive, free-swim­ming technology that measures the acoustic activity associated with leaks and gas pockets in pressurized pipelines. When acoustic anomalies are present, the data is analyzed to determine if it is a leak, gas pocket, or just an external sound.

Regular leak detection inspections can help util­ities identify leaks that may not be visible at the surface. By repairing leaks, utilities can reduce their non-revenue water and prevent pipeline failures, as leaks are often a preliminary indi­cation of pipeline deterioration. Location and elimination of air pockets is also beneficial as it reduces pressure on pumps that are attempting to pump water past a gas pocket.

For the structural inspection, TRA used PipeDiver®, a free swimming electromagnetic tool that identifies wire breaks in PCCP and bar breaks and broad areas of cylinder corrosion in BWP using electromagnetic technology. The tool oper­ates while the pipeline remains in service.

Although BWP looks similar to Prestressed Con­crete Cylinder Pipe (PCCP) in cross section, their design and materials are significantly different. PCCP is a concrete pipe that remains under compression because of the prestressing wires, with the thin-gauge steel cylinder acting as a water membrane. With BWP, the cylinder plays a much larger role in the structural integrity of the pipe. BWP is essentially designed as a steel pipe with mild steel used to manufacture the steel cylinder and steel bars.

As a result, the bar in BWP and wire in PCCP respond differently to environmental conditions that facilitate corrosion. The high strength steel wire in PCCP is smaller in diameter and wrapped under higher tension, therefore corrosion makes it quite vulnerable to breakage. The mild steel bars in BWP are thicker in diameter and wrapped under less tension, therefore corrosion takes sig­nificantly longer to lead to breakage.

The engineering services portion of the project was completed to identify optimal operating conditions for the pipeline and determine the structural performance of the pipe materials. This included creating performance curves for TRA’s BWP, as well transient pressure monitor­ing.

The BWP structural performance curves allowed TRA to determine which pipe sections to exca­vate and verify. By determining the bar break yield limit for the specific pipe material, TRA was able to identify which pipe sections should be immediately addressed and which could remain in safe operation.


The SmartBall® survey identified four leaks and three gas pockets. Although the four identified leaks were small (less than 2 gallons per minute), one was located in the front yard of a brand new church building and could have caused signif­icant water damage had it not been repaired immediately by TRA. Water from this leak was visible at the surface 325 feet away from the actual leak location.

The structural inspection using PipeDiver® iden­tified four PCCP pipes with electromagnetic anomalies resembling wire breaks. The inspec­tion of the BWP identified 14 pipes with bar break damage and 72 pipes with electromagnet­ic anomalies resembling cylinder defects out of 1,284 inspected pipes.

TRA has verified and repaired three sections of BWP that were beyond the yield limit deter­mined by the structural performance curves. Upon verification, TRA and Pure determined that distress areas identified in the inspection were accurate and the excavated pipe sections had bar breaks and corrosion.

By repairing specific pipe sections with dete­rioration, TRA was able to avoid replacing the entire 8.5 mile pipeline at a high capital cost. Completing condition assessment has also allowed TRA renew its pipeline infrastructure and continue providing reliable service to cus­tomers in the region.