A Tale
of Two Contractors
Leak Detection Improves Pipeline Quality and
Reduces Project Costs
in Big-pipe Country
By David Stewart Jones
A pipeline contractor won a utility contract to install a 28-mile stretch of 48-in. steel pipeline in rural Texas. Installing the entire pipeline took a 20-man crew about one year to complete. Stipulated in the contract was that the completed pipeline had to pass a pre-commissioning hydrostatic pressure test before acceptance by the utility. However, the pressure test revealed dozens of leaks all along the length of the installed pipeline. The contractor struggled for six months to find and fix the leaks, but the pipeline still failed to pass the hydrostatic pressure test. After discovering evidence of poor construction quality and several collapsed pipe sections, the utility finally lost patience and fired the contractor.
Elsewhere in Texas, the same contractor was getting the axe from a different water utility over a 108-in. pipeline project that also would not pass pre-commissioning hydrostatic pressure testing after months of trying. The contractor went bankrupt and both utilities hired a replacement pipeline contractor who operated quite differently. Rather than tediously filling and draining pipe sections to detect leaks with hydrostatic pressure testing alone, the new contractor had the pipelines tested for leaks using Sahara, a leak detection tool designed for live inspection of large-diameter water mains that accurately locates even the smallest of leaks in a pipeline.
Sahara was developed by the Pressure Pipe Inspection Co. (PPIC), an international company with offices in Dallas, Toronto, Canada, and Mexico City, Mexico, specializing in developing large-diameter water and wastewater pipeline condition assessment technology and leak solutions. Sahara’s ultra-sensitive acoustic sensor actively detects and precisely locates the smallest of leaks within new pipelines and sewer mains sized 12 in. or larger. Inserted directly into a pressurized water pipe through a 2-in. tap, the leak detection tool detects the location of water leaks within inches while pulled through the pipeline by a small water-driven parachute or a high-tensile strength mule-tape cable. The sensor transmits an acoustic signal to the surface, where the data is collected and immediately analyzed by a field technician.
“We had a 10-mile section of pipeline that appeared to be leaking because of water observations on the surface,” says David Marshall, Engineering Services Director with the Tarrant Regional Water District (TRWD). TRWD is one of the largest water suppliers in Texas with four reservoirs and more than 150 miles of pipeline servicing more than 1.7 million people. With such an extensive high-pressure, large diameter pipe raw-water transmission system, TRWD has relied heavily on Sahara for pipe integrity testing. “Instead of digging, we used Sahara to test the pipeline. Sahara found that none of our pipe joints were actually leaking — it was all just ground water that was coming to the surface,” says Marshall.
Though Sahara is typically deployed to detect leaks in existing pipelines, TRWD is now using Sahara for a proactive means to ensure new pipelines are leak-free on their first day of operation. “We had 20 miles of brand-new pipeline we wanted to ensure was drip-tight before subdivisions and highways were built over it,” says Marshall. “We learned from the pre-commissioning Sahara inspection that our pipeline installation and welding quality control was very, very good — 20 miles of pipe and only one tiny leak.”
Contractors like TRWD are discovering the advantages of using Sahara for pipeline testing. Sahara avoids the need for mass pipeline excavations, helps keep troubled projects on track, and — most important for many contractors — Sahara helps maintain a stellar professional reputation with demanding utility clients.
“Since the mid-1990s, Sahara has been successfully deployed in hundreds of pipeline insertions, finding more than 2000 leaks in over 1,000 miles of pipeline worldwide,” says Dr. Brian Mergelas, President and CEO, PPIC. “Water utilities using Sahara to inspect and repair the leaks typically get a return on investment of four to more than 10 times the amount of money they spent on the entire program.”
Pipeline Pre-commissioning Testing
“Sahara is the most cost-effective approach for pipeline pre-commission testing,” says Rusty Gibson, Consulting Engineer with the design and engineering firm Freese and Nichols. “However, today’s contractors are not generally doing pipeline pre-commissioning testing. They’ll bring in leak-detection tools like Sahara only if they’ve got a problem — or if the utility requires them to.”
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| Inserted directly into a pressurized water pipe through a 2-in. tap, the leak detection tool detects the location of water leaks within inches while pulled through the pipeline by a small water-driven parachute or a high-tensile strength mule-tape cable. |
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When a pipeline fails the pressure test, it is generally the contractor’s responsibility to fix it. But Gibson maintains that design engineers and utility owners — not contractors — are behind the trend toward more thorough pre-commissioning inspections. “Owners are getting smarter about their investments,” says Gibson. “They are discovering how cutting-edge technologies like Sahara can enhance the value and longevity of their pipelines.”
Gibson believes that there is a growing number of industry examples where leak-detection solutions are being leveraged to cut costs associated with project specifications. A utility seeking a drip-free 84-in. steel pipeline specified expensive double-welded joints — both inside and outside the pipe — to absolutely ensure that the pipeline passed the pre-commissioning pressure test on the first try. Engineers proposed a cheaper solution: Use a single interior weld tested by PPIC’s Sahara instead of the much more expensive double-weld solution. Gibson says there’s a lesson here for contractors. “If a contractor sees something like this in his specifications, he may want to propose a change order to cut installation costs by using Sahara. It saves the owner money — and it saves the contractor money, time and hassle.”
“Allowable Leakage” No Longer Allowable?
Contractors are typically paid by utilities only after their completed pipeline passes the specified pressure testing. Contractors are not required to find and fix all the leaks in a pipeline — just those leaks that cause the pipeline to fail the pressure test. Industry critics point out that this “allowable leakage” standard — as much as 10 to 15 percent leakage — no longer fits with today’s conservation mindset and water-shortage market realities.
“Utility owners are recognizing that allowable leaks aren’t really allowable anymore,” says Rusty Gibson of Freese and Nichols. “Water has become too precious to spill, and many utilities are adopting extensive leakage control programs. Utilities are now regularly using Sahara leak detection, and the total cost of running such a test on an entire length of large-diameter pipeline is a very small fraction of the overall cost of the pipeline.”
“Using Sahara leak detection, PPIC’s condition-assessment technologies has saved us from overreacting and replacing entire pipeline systems,” says Marshall. “Instead of spending $150 million on a pipeline replacement, PPIC helped us spend only $14 million on pipeline rehabilitation.”
Another advantage to using Sahara is that Texas is big-pipe country, according to Marshall. The noise of flowing water in a large diameter pipe masks the sound of a small leak, and the larger the pipe, the harder it is to find it with any leak detection system other than Sahara.
David Stewart Jones is a Freelance Environmental Technology Writer and Researcher based in Toronto, Canada. Correspondence can be sent to dsjonz@hotmail.com.
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