Pipes: Locate and Evaluate

Sept. 13, 2013

By Lyn Corum

Water agencies are growing ever more sophisticated in their adoption of new technologies and information systems to digitally map their piping infrastructures, initiate inspection and replacement schedules, and maintain them through a sophisticated geographic information system, or GIS.

Many of the water agencies are relying on the new technologies, developed by private companies, to control costs as they face aging infrastructures. These agencies are finding that once they know what needs to be replaced, they can use asset management tools to prioritize capital expenses as part of long-term planning.

Echologics, a division of Mueller Co., has become very popular with water agencies around the country. Marc Bracken, vice president and general manager, says, “We find what is important is the extension of asset life.”

Cast iron pipes have more life than water agencies think, and there may be opportunities to rehabilitate them. It costs $1 million to $2 million to replace one mile of typical distribution mains, Bracken says.

Water agencies used to use leak data to evaluate the structural integrity of their pipelines. Bracken characterizes this planning as, “If there are more than two leaks in a street, it’s time to replace the line.”

PVC pipes are useful for many types of water main installations, depending upon the specific needs and site challenges faced by the utility.
The frequency and failure of previously installed water mains has forced many water agencies to initiate large-scale infrastructure rehabilitation and repair.

He says one of the tools used to evaluate pipe systems is the desktop model, in which “We do an evaluation of the paper records. If the city doesn’t have good records, “we will have to start from scratch by identifying the worst performing pipes. We then make recommendations as to what to do.”

Starting with acoustic pipe testing technology, Echologics will survey 5 to 10% of each pipe type to determine its residual thickness. Acoustic sensors are installed on valves or fire hydrants, and they measure velocity of sound. As pipes get older, the acoustic sounds slow down. Usually, galvanized steel is the worst performing, then thin wall cast iron. Older pit cast pipes are better performing because pit depths develop in fractions of inches per year, he says.

The company also uses ground-penetrating radar (GPR) to locate and check the density of concrete pipes. GPR can’t see through clay, and it doesn’t show what material the pipes are made of, but it can see them. Electromagnetic technology using remote field eddy current can be used to map metallic pipelines. However, it is expensive and intrusive, Bracken says.

All information collected goes into GIS software. Each pipe segment gets a grade (number of times broken, structural condition, prediction of remaining life). Most large water agencies do have GIS software, but not a lot of smaller utilities do, says Bracken.

There are various software packages, and Bracken mentioned RIVA that accepts GIS data. The software optimizes the water agency’s capital spending plan allowing water agency managers to know how much they will have to spend, he says.

Location Assessment Evolving
Greg Scoby, a consultant and former engineering manager of the City of Palo Alto’s (CA) water department, described several methods of assessing pipes. However, a lot of mapping methods are limited by pipe materials, he says.

Paint marks on streets are the traditional way of marking where utilities (water, electrical, gas lines) are located so that contractors will know what is underground when they start planning digs. Old records of pipelines usually did not have reference points or the references have disappeared. Using a GPS technology can create digital records when new pipes are installed or old ones are repaired.

Scoby says a method used in the 1970s before GPS technology was introduced used tracer copper wire with insulation laid next to polyvinyl chloride pipe and brought up to the valve box. A noise generator using a very low frequency traveled along the copper wire, thereby identifying a pipe’s location.

Fifteen years ago, says Scoby, 3M created marker balls with antennas that are placed as close to the pipe as possible where a GPS point can be captured using radio frequency IDs. The company makes a different colored marker ball for separate utility line; blue marker balls are for water pipes.

Plastic pipe installations were popular in the 1960s, and ground penetration radar came into use to find them, says Scoby. Mala Geoscience commercialized the technology in 1990 which can work on sand and ice among other soil types that absorb radar signals. GPR works better the larger the diameter of the pipe, say 36-inch water mains. This technique couldn’t be used on pipes up to 4 inches he says.

In Europe, Scoby adds, water agencies are using 3D imaging using four to six antennas attached to the front of the truck. As the truck drives down the road, the antennas spread across the width of the road to capture images of all utilities below ground level.

He says, while in Palo Alto, he did subsurface engineering as much as possible. It is better to prospect by making a hole in the street and sucking out the dirt. The better story you can give to contractors, the better the outcome. Projects get out of hand when there are unknowns, he says.

GIS programs provide a graphical means of asset management, Scoby says. Bar codes can be installed on the outside of a pipe during installation in the field. The bar codes have information that tell the size of the pipe, who manufactured it, and the date the pipe was installed. GPS coordinates; the bar code information and the badge number of the installer can then be entered into the GIS software.

Underground Infrastructure Technology (UIT) is a subsidiary of Caterpillar, and Mark Wallbom is CEO. “We’re in the business of mapping the subsurface–in the top 20 feet–using every geophysical method commercially available, plus some of our own,” he says.

UIT has a patent pending on a new 3D technology that will allow a utility manager or a contractor preparing to do street work to see a digitally generated picture of the underground utilities via a smart phone or tablet. Called “augmented reality,” VTN Consulting, working with UIT, recently completed a pilot for the City of Las Vegas that is considering mapping all of its subsurface utilities using this technology.

GPS data with identified locations and depths of piping is uploaded into the Internet’s “Cloud.” Once turned on, the smart phone or tablet knows where the user is, and with the app UIT is developing, the GPS location of the two will be linked. As the user walks down the street, the view of the piping system below appears on the screen he or she scans the area through the lens of the camera. The 3D view of the underground utilities are overlaid or “augmented” on the screen, in real time, with the displayed data being continuously updated as the user changes his or her point of view.

Keeping Track of Assets
Sweetwater Authority provides water to National City, the western portion of Chula Vista and Bonita immediately north of San Diego Bay in southern California in a service territory of 41 square miles. It serves 188,000 customers and 33,000 meters. The original water agency began as privately owned Kimball Brothers Water in May 1869.

Sweetwater Authority, a joint powers authority and a member of the San Diego County Water Authority (SDWA), was organized in February 1972 and began operating the water system in August 1977 after purchasing the water assets from the last private owner, American Water Company.

A water main replacement
PVC pipes ready for installation

Sweetwater authority owns two reservoirs, Loveland and Sweetwater, capable of storing 17 billion gallons of water, enough to supply Sweetwater customers for about 24 months. However, because of the ongoing drought in southern California it has had to buy its water through SDWA for the past year. The reservoirs are at 35% and 25% capacity, respectively.

For the past 30 years, the Sweetwater Authority has been replacing its cast iron pipes with polyvinyl chloride pipes. When it took charge of the water system in 1977, Sweetwater was repairing 200 leaks a year in the cast iron pipes. Hector Martinez, engineering manager in charge of the capital improvement program says the former owners ignored the pipe system and were more interested in profits. Currently, they have less than 10 leaks per year, he says.

Now that all the old cast iron pipes have been replaced, Martinez and his staff are concentrating on repairing and replacing their asbestos concrete (AC) pipes that make up 75% of the 387 miles of pipelines. Steel pipes make up 10%, while PVC are 15% of the total.

Martinez says they are replacing sections at two miles a year and want to do four miles a year. “We don’t have a crisis to replace the AC pipes, so there is time to decide” what needs replacing, he says. The main reason to determine the remaining useful life of these pipes is they make up 75% of the pipe system.

Enter Echologics. Sweetwater hired the company in 2012 to test 10,000 feet of AC pipe with its acoustic pipe testing technology. Sweetwater cut seven pieces of pipe out based on Echologics’ data and sent the pieces to the MEIZ laboratory in Oregon to either confirm or correct Echologics’ estimates of remaining useful life. Echologics says the pipes tested had 80 years of life left, and MEIZ reported 60 years. Sweetwater arranged a meeting with the two companies and got them to converge in their results, says Martinez.

Martinez says AC pipes are doing great in southern California, but in Napa–in northern California–it appears that the acidity in the soil is eating up the pipes. The data Sweetwater and Echologics gathered were shared with the East Bay Municipal Utility District near San Francisco and the American Water Works Association that are completing a $2.4 million study on predicting the remaining useful life of AC.

Sweetwater has become comfortable with Echologics’ data and has signed the company on for the next phase of its work testing 13,000 feet of AC pipe to determine remaining useful life. It decided not to verify Echologics’ results by a third party in this go-around, says Martinez.

Bracken gave more details of Echologics acoustic testing technology. Pipe wall thickness is measured as sensors track the velocity of sound traveling through the pipe. The distance between sensors is contingent on a number of factors including pipe material and the level of outside noise due to traffic or nearby pumps, for example, says Bracken. A sound is generated either by turning on hydrant water or tapping on the valve or hydrant. The sounds are captured on a computer as they travel through the pipe. As pipes get older and thinner, the acoustic sounds slow down.

The sound data identifying pipe wall thickness, plus location and type of the pipes, valves, and hydrants is fed into Sweetwater’s GIS system. Debra Stein, GIS Specialist at Sweetwater, explains that it uses its GIS system to determine what water mains should be replaced based on age, size, whether it’s in a residential area or commercial district. This system is used on a daily basis to determine maintenance schedules and tracking of repairs, etc., on all its assets.

PCCP Mains Were Bursting
Washington Suburban Sanitary Commission (WSSC), established in 1918, and headquartered in Laurel, MD, provides water services to 1.8 million residents living in Montgomery and Prince George’s Counties. It has 5,600 miles of water pipes–cast iron, ductile iron, polyvinyl chloride, or PVC, and prestressed concrete cylinder pipe (PCCP). It acquired a pipe system already in existence in 1918, and some cast iron dating from the 1920s is still in the ground.

WSSC, faced with nine large prestressed concrete water mains blowing up since 1996, developed a sophisticated inspection and evaluation process to identify mains which were deteriorating and near failure. It has spent $21.2 million on pipe detection since then.

Fred Pfeifer, asset strategy manager for the water network, says about two years ago the commission began inspecting about 160,000 sections of distribution and transmission water pipes and developed models that predicted when the pipes would break. Each section of pipe was examined to determine the risks of breakage or leaks. The agency has had inspection programs for a long time, he says, and as technology improves “we are proactive in using it.”

Pfeifer estimated that the agency will eventually track approximately 750,000 distinct infrastructure assets in its asset management system.

Because testing distribution systems can be expensive, to validate its models the water agency hired Echologics in March 2012 to complete a pilot survey. Echologics assessed more than 17,500 feet of distribution mains (under 16 inches in diameter) that were scheduled for replacement at an estimated cost of $2.9 million. However, Echologics found that approximately 70% did not need to be replaced as their remaining wall thicknesses were in good shape or at or near their original condition.

WSSC then validated Echologics’ results after submitting some of the pipes to forensic testing. Echologics’ contract was renewed to assess the condition of an additional 35 miles of cast iron distribution lines ranging from 6 to 14 inches in diameter. WSSC will use this data to identify sections of pipe that are in the poorest condition and prioritize their replacement.

Meanwhile, WSSC hired Pure Technologies to monitor its PCCP transmission lines larger than 48 inches. Pure Technologies’ inspection robots, such as the PipeDiver, PipeCrawler or PipeWalker are inserted in the water main, and as a robot travels down the pipe it creates an electromagnetic field that detects where wires are broken. A computer monitoring system collects these sounds for later analysis.

Of the 7.9 miles of PCCP water mains, 2,574 sections were inspected, and just 1.2% needed attention–only two sections required replacement, says I. J. Hudson, WSSC’s Public Affairs Unit Coordinator.

Hudson says the first phase was completed earlier this year and in the fall Pure Technologies will inspect 36- and 42-inch PCCP mains. He says starting in fiscal year 2015 the water agency is going to inspect, repair or replace 55 miles of pipe per year for the feasible future. In this rotation, each main is scheduled for inspection every five to seven years.

Felicia James, an asset strategy manager at WSSC, says all the data collected is fed into the agency’s asset management system including maintenance records and history. The GIS database graphically illustrates the pipe system in place of paper maps. All of this is used to refine decisions on investments.

GIS Is the Solution
Tarrant Regional Water District is a raw water supplier to cities and has provided water for more than 80 years to more than 1.7 million customers in north central Texas, including the city of Fort Worth.

Tarrant installed 164 miles of PCCP in its system in the 1970s and 1980s, and the frequency of failures began to increase in the late 1980s. The water district began extensive inspections of its pipes in 1999, with the intent to map the entire system, according to Courtney Jalbert, a meteorologist and analyst with the water district.

Jalbert coauthored a paper, “Pipeline Asset Management using a GIS Solution” along with Peter Nadini & Mehdi Zarghamee with the engineering firm Simpson Gumpertz & Heger Inc. (SGH) and Mike Garaci at Pure Technologies. It was presented at the ASCE Pipelines conference. Most of the details below were taken from that paper.

Tarrant hired Pure Technologies to inspect all of the 72- to 108-inch PCCP water mains using its electromagnetic technology and was able to get an accurate count of broken wire in the pipes. Both quickly realized Tarrant’s maps were inaccurate. During inspections, each section was assigned a specific identification number and GPS coordinates for surface features including air valves, blow offs, and manholes.

Pure Technology’s electromagnetic inspection technology, such as the PipeDiver or PureRobotics, which move remotely through a water main, functions much in the same way as a radio transmitter and receiver. The transmitter produces an electromagnetic field, and the prestressing wires in the pipe amplify the signal that is recorded by the receiver. If there are broken wires, the signal is distorted. A measurement of the distortion quantifies the number of broken wires.

In 2001, Tarrant joined with seven other agencies (the PCCP Users Group) to employ SGH, a nationwide engineering company, to develop risk curves and better define pipe replacement based on wire breaks due to corrosion.

SGH also evaluated pipes with wire breakage due to embrittlement. These kinds of wire failures differ from corrosion in that the breaks are located randomly along the pipe length and around the pipe circumference.

In 2006, Tarrant asked Pure Technology and SGH to integrate the inspection data and pipeline operation data that were currently in Tarrant’s GIS database with SGH’s failure risk analysis curves to evaluate the risk of pipe failure. This upgraded tool used the most recent electromagnetic inspection results and maximum pressures in the pipeline from different hydraulic working and transient conditions.

Since completing its inspections of all 164 miles of PCCP, which took 10 years, Tarrant now has an accurate map of the pipeline segments, hydrants, valves, and inspection results. This map forms the foundation of the water district’s GIS database giving it analysis capabilities.

The GIS database allows Tarrant to prioritize pipe replacements each year based on the results of failure risk analysis. It integrates all information into the GIS database including land use, soil conditions, utility networks, right-of-ways, parcel ownership, and aerial photography.

Tarrant has since expanded its inspection program to a full asset management program consisting of periodic inspections using electromagnetic technology, on-demand calculation of failure risk based on the latest inspection results, and the GIS data base to process, store, and present the latest evaluation results for repair prioritization.

Tarrant uses transient pressure control, cathodic protection, and pipe segment replacement to help mitigate failures on its water mains: Pump control valves were modified, so a programmable logic controlled the valve closing times reducing transient waves dramatically. Next, cathodic protection was implemented over a five-year period using zinc anodes attached to the pipelines. Finally, segments could be selected for replacement based on known breaks and ranking as areas of distress are identified on the GIS map.

Jalbert reports that Tarrant’s engineering director, David Marshall, calculates that two of its pipelines (Cedar Creek and Richland) could have been experiencing as many as 11 and 30 failures per year, respectively. Once Tarrant’s mitigation efforts were established, the failure rate was reduced to 0.5 and 0.1 failures per year, respectively.

Tarrant values its pipeline infrastructure at approximately $900 million. The water district carries out its own pipe segment repairs that, on the average, cost about $40,000. It estimates that replacing the 300 highest-priority segments would cost around $12 million spread out over a number of years, which is significantly less than the costs associated with replacing catastrophic failures.

Tarrant uses a three-year horizon for its pipeline inspection and replacement process based on the GIS database, which prioritizes future segment replacement needs. The water district’s asset management program concentrates repairs on the pipes at highest risk of failure. This facilitates planning and budgeting and has spread pipeline maintenance costs over a number of years to ease funding issues.

The conference paper concluded, “With an asset management program in place, the lifespan of water transmission mains can be greatly increased, risk exposure reduced, and expenditures focused in areas of greatest benefit.”

Author’s Bio: Lyn Corum is a technical writer specializing in water and energy topics.

About the Author

Lyn Corum

Lyn Corum is a technical writer specializing in water and energy topics.

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