The acoustic sensor was installed in 2010 after an inspection of the pipe, which is five feet in diameter and lies under the eastern edge of Connecticut Avenue at Chevy Chase Lake Drive, according to the WSSC. The equipment is designed to detect the “ping” sounds that emanate from a concrete pipe as its reinforcing steel wire begins to snap, giving the utility time to shut down a pipe before it ruptures.
WSSC officials said they don’t know whether the sensor failed or the break was caused by something other than weakening wires. A problem in a steel joint, where there are no reinforcing wires, would not be detected by the sensor, WSSC officials said. A pipe also can break suddenly if its supporting bed of soil beneath it erodes.
The equipment is part of a break-detection system that the WSSC has spent $21.2 million on since 2007 to warn of weaknesses in its largest aging underground water mains, which are considered particularly dangerous because they are highly pressurized and can explode without warning. The break in the 33-year-old Chevy Chase pipe, which occurred about 8 p.m. Monday, sent a geyser of water four to five stories into the air and blasted through asphalt on Chevy Chase Lake Drive, leaving a 20-foot-deep crater.
WSSC spokesman Jim Neustadt said it will take several months for a forensic investigation to determine the exact cause of the break. He said it occurred in an area where the 60-inch main joins a 54-inch pipe, but he said he didn’t know whether that would prove significant.
“Nothing is perfect,” Neustadt said of the break-detection equipment. “You take the best technology and the best knowledge you have, and you put it to use in the best way you can.”
He said that it was the first time a WSSC pipe with the break-detection system had burst but that the WSSC has known that no technology is “fail-safe.”
Across the country, local officials are struggling to maintain and replace aging water and sewer systems.
Another break, of an eight-inch water main in Bethesda, on Tuesday morning closed River Road between Bradley Boulevard and Persimmon Tree Road for much of the day, snarling traffic.
Travis Wagner, a vice president for Pure Technologies, the Columbia company that is installing and monitoring the acoustic equipment for the WSSC, said Tuesday afternoon that he hadn’t been able to inspect the Chevy Chase pipe or his company’s equipment. Wagner said the company has installed the equipment in 560 miles of pipe worldwide since 2005 and has never failed to detect a weakening main in time for a utility to intervene.
“We’ve never had an issue detecting a wire-break-related failure,” Wagner said. “I know WSSC’s goal is to find out [the cause of the break] as soon as possible. There are a lot of questions.”