A last-ditch effort on July 16 by two Washington Suburban Sanitary Commission technicians to close a stubborn, corrosion-covered valve for water-pipeline diversion enabled the Washington, D.C., area water-wastewater utility to bypass the rapidly failing main. Closing the valve averted an extended service outage in a densely populated section during excessively hot weather.
The 54-in.-dia reinforced-concrete high-pressure transmission line, installed in 1966, supplies 10 million to 15 million gallons a day to more than 100,000 users in a large portion of Prince George's County, Md., including residences, Andrews Air Force Base and the National Harbor mixed-use complex adjacent to the Potomac River. Acoustical tests taken in mid-July showed that 37 strands of reinforcing wire had broken, indicating a failure—potentially in the form of an explosion—was imminent. WSSC, which dates to 1918, now serves 1.8 million people in the county and neighboring Montgomery County with a network of nearly 5,600 miles of freshwater pipeline.
It is unknown when the valve was last tested, but prolonged exposure to acidic soil had frozen its gears, says WSSC. Previous repair efforts had failed, so the utility began a fast-tracked plan to close a three-mile pipeline section for emergency repairs. As the scheduled July 17 outage approached, WSSC facility technicians Brad Destelhorst and Thomas Ecker volunteered to make a final repair attempt.
For 12 hours, the two worked in a cramped, partially flooded vault with hand tools, managing to fully close the valve, which allowed water to be diverted to a smaller, secondary transmission line. Less than one mile of the failing pipeline was out of service. The action allowed WSSC to cancel the outage alert, although a water-conservation mandate continued until transmission-line repairs were completed. WSSC CEO Jerry Johnson said the workers' effort was the first time such an operation had been tried.
Sudden failures of 40- to 50-year-old reinforced pipe have been a problem for WSSC. The agency says the pipes failed because they were reinforced using tightly wrapped steel wire, a practice that is no longer accepted. The firms that manufactured the pipe in the 1960s and 1970s have since gone out of business. WSSC says that, although less than 2% of its concrete pipes are of suspect construction, repairing those lines would cost close to $3 billion. The agency relies on acoustical monitoring and other inspections to head off potential failures.