An article in the Washington Post highlights the struggles of the Washington Suburban Sanitary Commission (WSSC) in maintaining and upgrading water mains in Montgomery and Prince George’s Counties.
The Washington Suburban Sanitary Commission has 350 miles of concrete mains that have been prone to exploding without warning. The particularly large mains are designed to carry high volumes of pressurized water. Utilities around the world have struggled with this type of pipe since the 1980s, when they began bursting decades before their 100-year life expectancy was up.
The WSSC’s inventory of large concrete pipe is second only to Detroit’s and two to three times that of many other U.S. cities and suburbs, according to a Washington Post survey of 21 large utilities.
While local officials work to protect residents who live in areas prone to water main breaks, they must also balance the costs of upgrades.
The scope of the problem has been a key question among local officials wrestling with how to best protect people who live, work, attend school and drive within what the utility has declared an 80-foot danger zone of the massive mains’ potentially explosive forces.
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,” said Gary Gumm, the WSSC’s chief engineer.
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. After decades of development, some of the mains, buried in what was once the countryside, now sit just beyond back fences and alongside or beneath major roads.
In the densely populated Washington suburbs, they’re too big to move, WSSC officials say, and 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, WSSC officials said.