D.C. Area Utility Tackles Aging Infrastructure
Last year, the Washington Suburban Sanitary Commission celebrated its centennial—a milestone that marks the utility’s long experience in water and wastewater and illustrates the daunting challenge it faces to maintain a large inventory of aging infrastructure. WSSC has grown to be the eighth-largest U.S. water and wastewater utility, serving approximately 1.8 million residents in Montgomery and Prince George’s counties in the Maryland suburbs of Washington, D.C. Its system covers nearly 1,000 square miles and includes 5,768 miles of fresh-water pipeline and 5,578 miles of sewer pipeline.
Among WSSC’s greatest challenges is the pressing need to repair, replace or rehabilitate aging pipelines. More than one-third of its water mains are more than 50 years old, effectively at or near the end of their expected life spans. In recent years, WSSC has drawn on decades of experience and a desire to pursue forward-looking solutions to aggressively address infrastructure issues. In light of its efforts, ENR MidAtlantic has named the Washington Suburban Sanitary Commission its Owner of the Year.
John Mitchell, WSSC pipeline construction division leader, says that in the past, the utility typically took a conservative approach to its work, but it is increasingly embracing innovation to develop better, faster and less expensive means and methods. Historically, decisions about which pipes need to be replaced were based on factors like age, soil conditions and work history. Today, WSSC uses a variety of technologies to more accurately pinpoint pipes needing replacement. “We’ve got to be smart,” Mitchell says. “With as many miles of pipe as we have, we can’t afford to just go out and start replacing pipes that may have additional life in them.”
To help monitor its prestressed concrete cylinder pipe (PCCP), WSSC began installing an acoustic fiber optic cable (AFO) system in large diameter PCCP more than a decade ago. The cables float inside pipes and monitor for acoustic “pings” that indicate breaks in the pipes’ reinforcing-steel wires. WSSC has 145 miles of PCCP, ranging from 36 in. to 96 in. in diameter. As of 2018, 102 miles of the pipe were monitored with AFO—making it the longest AFO monitoring system in the country, according to WSSC. The monitoring system includes other technologies, such as Pipe Diver, a long-distance, free-swimming condition assessment tool that can be used while pipelines are in service.
WSSC reports that between 2010 and 2018 the monitoring system, which cost $21 million to install, identified 20 damaged pipes. By allowing crews to make proactive repairs rather than expensive emergency fixes, the utility estimates that the effort resulted in a cost saving of $42 million. In addition, inspections showed that about 95% of the monitored pipes were in “like-new” condition. Less than 2% required immediate rehabilitation or replacement, according to Pure Technologies, the system provider.
As WSSC enhanced its monitoring efforts, it also began to ramp up its water main replacement program. By fiscal year 2012, WSSC was replacing more than 50 miles of water main annually. The program peaked at 65 miles of pipe replacement in fiscal 2017.
Mitchell says that in recent years, the program was able to focus on the “low-hanging fruit” in identifying its replacement needs. The remaining pipes, particularly those with smaller diameters, are more challenging to monitor. He says, “We will back off on our mileage in the next few years to about 25 miles per year, while we explore new technologies to assess the condition of pipe—and then we will start to ramp up again.”
As part of its water main replacement program, WSSC also began specifying zinc-coated ductile iron pipe to help extend the life of its pipes by better controlling corrosion. Zinc-coated pipes have been used in Europe for decades, but have only been installed by major U.S. utilities in the past decade.
WSSC also specifies that its pipes must be wrapped in V-Bio enhanced polyethylene encasement for an additional external layer of corrosion control. WSSC expects that pipes specified with the two materials will last at least 100 years, compared with conventional iron ductile pipe’s expectancy of 50-plus years. WSSC claims that it is the first utility in the U.S. to specify a combination of the two materials.
Given the pipes’ unusual nature, Dan Hamilton, construction manager in WSSC’s pipeline construction division, says that sourcing pipes and getting them delivered just in time on projects was initially a challenge. “Contractors were supplying materials at first, but now we’re at the point of supplying most of the pipe on our own directly through our relationships with manufacturers,” he says.
Dennis Funk, senior project manager at engineering firm Gannett Fleming, says that, in recent years, he has seen WSSC become more progressive in how its manages its assets. “They put a lot of thought into what they do before they jump in, but I’ve found them to be very open to different ideas and approaches,” Funk says.
Steve Ford, vice president of the Mid-Atlantic region for Garney Construction, says he has seen WSSC evolve since his company began doing large projects for the utility more than three decades ago. “Back then and today, it’s fair to say that they have very high expectations,” Ford says. “The difference is that they were more rigid and less open to change when we started with them. They are not quick to change now, but when they do implement innovations, the focus is on asset management and making sure the assets they put in the ground will last a long time.”
Garney is one of 10 companies that are in a WSSC indefinite delivery/indefinite quantity contract pool, which the utility typically uses for smaller projects. It turns to traditional design-bid-build delivery for larger pipeline projects. Ford says that Garney and other companies look forward to seeing WSSC use more alternative-delivery methods in coming years.
Theon Grojean, WSSC facility design and construction division leader, says the unit has let a few projects under a construction manager at-risk method. It is currently testing a range of design-build projects, including one valued at $220 million and one of $5 million.
Hamilton says the pipeline division will review the results of the facilities division’s alternative-delivery pilot projects and determine how they could be applied to pipeline work.
Looking ahead, WSSC is targeting additional opportunities for innovation. For nearly a year, it has encouraged employees to brainstorm, research and identify new ideas that the utility can implement in the coming years. WSSC will hold an “Innovation Day” in May, at which employees can pitch suggestions.