Many of the WSSC's large concrete mains were installed during the 1970s, when industry standards in place at the time permitted design and manufacturing changes that were later found to make the pipes significantly more prone to breaking. The WSSC also has significant amounts of pipe from a defunct New Jersey company blamed for making some of the most vulnerable mains during the 1970s and 1980s.
The pipes span up to eight feet in diameter, big enough to hold a minivan. Because they carry so much pressurized water, they can blow like a bomb, leaving 50-foot craters in roads and hurling rocks and other debris like shrapnel.
The 350 miles of large concrete pipe — technically called prestressed concrete cylinder pipe — form the backbone of the 5,600-mile water distribution system for 1.8 million people in Montgomery’s and Prince George’s counties. The large transmission mains carry water from the treatment plants to the smaller pipes that reach into neighborhoods.
According to WSSC officials, replacing all of them would cost a prohibitive $2.9 billion. Doing so also wouldn’t be cost-effective because inspections have shown that only 1.5 percent of concrete pipe sections need to be repaired or replaced. According to a recent Environmental Protection Agency estimate, the nation’s water distribution systems will require $384 billion over the next 20 years to keep drinking water safe.
The WSSC, on the other hand, must move water across 1,000 square miles. Most of the utility’s water comes from the Potomac River, on the western border of its service area. The rest comes from the Patuxent River, at its eastern edge.
Moving 170 million gallons of water daily around the Capital Beltway, up toward the Frederick and Howard county lines, and down into southern Prince George’s with enough pressure to run showers and flush toilets required hundreds of miles of large pipe.
The District has 37 miles of concrete pipe. The city’s older water system was mostly built out by the time concrete pipes became widely used.
The WSSC now has 77 miles of concrete pipe monitored by the acoustic equipment — the most of any U.S. water utility, according to Pure Technologies, the Columbia-based firm that patented the technology. The system provides alerts of a wire break almost daily.
The WSSC is about to begin using robots to inspect 68 miles of smaller concrete mains. Those pipes also will have acoustic equipment installed for monitoring. (Wash Post, 6/23/2013)