The Washington Suburban Sanitary Commission has formed an ad hoc committee to discuss safety measures developers should follow when building near the utility’s aging water mains.
Gary Gumm, a chief engineer at WSSC, told the committee Tuesday afternoon that large water mains — from 3 feet to 8 feet in diameter — can fail “catastrophically.”
“When these pipelines fail, they fail very quickly,” Gumm said.
Gumm likened a water main break to chopping a garden hose with a meat cleaver. Smaller pipes would be able to hold together if they sprung a leak, he said, but larger mains tend to split.
The resulting explosion is capable of throwing debris over 200 feet, according to WSSC documents. The utility proposed that developers should be required to build structures at least 80 feet away from large water mains.
WSSC decided last summer not to enforce the requirement, pending further review. At the time, the setback would have affected about a dozen developers within WSSC’s service area, Gumm said.
The utility serves nearly 1,000 square miles in Montgomery and Prince George’s counties, providing water and sewer service to 1.8 million people, according to its website.
WSSC’s current design guidelines state that “special considerations and modifications may be imposed” for new developments proposed within 200 feet of the aging pipelines.
“Nobody really knows what this language means,” Gumm said.
Developers such as Westbrook Partners, who are working to bring together Gaithersburg’s new Crown community, interpreted WSSC’s guidelines to mean their homes should be built blast-resistant, in the case that a water main breaks. WSSC is not currently enforcing that requirement. The concept will be a topic of debate for the new ad hoc committee.
A few members of the ad hoc committee, which contains members of county councils, the Maryland National Capital Park and Planning Commission and the Maryland Municipal League, asked why WSSC doesn’t systematically replace the aging pipes.
The replacement costs of replacing water mains between 36 inches and 96 inches in diameter would be about $2 billion, Gumm said. The estimated down time for that work, when the pipes would be out of service, is over 215 years.
“It’s the time factor that really is the bigger problem,” Gumm said. County governments might be willing to allocate more of their budgets to replacing the pipes, but that doesn’t solve the issue of extensive down time, he said.
Through monitoring technology, WSSC is working to identify pipes that may fail. About 1.5 percent of WSSC’s inspected pipes require repairs.
“We’re trying to find those 2 percent before they actually fail,” Gumm said. “They still have to degrade to the point where we can pick that up.”
The ad hoc committee’s next meeting will be in June.