Montgomery County’s water mains have about 160 sections that contain similar vulnerabilities that caused a “catastrophic” water main break in March, leading to a massive crater on Chevy Chase Drive and a loss of 60 million gallons of water, Washington Suburban Sanitary Commission representatives said Monday.
According to a forensic analysis of the break, three simultaneous issues led to the failure: First, the wire used between two components of the 35-year-old reinforced concrete pipe had not been “pre-stressed” and was therefore weak. Second, chlorinated water had been slowly leaking from a gasket seal. And third, that leak had weakened the grout in the joint, allowing water to seep in, corroding the steel parts inside the pipe.
WSSC’s current detection system did not, and can not, pick up on these kinds of failures and a new inspection system must be created, said David Burke, group leader for technical services at WSSC at a meeting before the Montgomery County Council’s Transportation, Infrastructure, Energy and Environment on Monday.
Inspections of all the areas that have the same vulnerabilities will begin this fall, Burke said, but there are limits on how thorough those inspections can be, since so many water mains are buried in places that are difficult to access.
“There are numerous locations we can’t excavate,” he said.
While officials would not release the exact locations of the vulnerable sections, spokesman I.J. Hudson said that 17 of them were located on a 48-inch transmission line that runs through Montgomery County.
Originally, workers thought accumulating water on Chevy Chase Drive was due to a leaky valve and did repair work to correct that. But later on that evening, around 8 p.m. on March 18, the water main burst.
It turned out the problem was not a valve, but the 60-inch concrete water main. The break, at the southeast corner of the intersection of Connecticut Avenue and Chevy Chase Lake Drive, created a crater about 90 feet long and 45 feet wide and produced a 30-foot high geyser. Much of the 60 million gallons lost ran into Rock Creek, but large portions of asphalt and pavement were washed out, Burke said.
“What we’ve learned when we’re out looking at these valves for leaks, is if it’s connected right to a main line, make sure it’s not from the main itself,” said Gary Gumm, WSSC’s chief of engineering and construction.
That will require more time on each site, he said.
“In the future, we will do more testing when it’s in that situation,” said Derrick Phillips, the acting chief of customer care for WSSC.
The utility representatives admitted their workers had made a mistake, but were quick to point out this was the first time a break like this one had occurred in 70 years.
Councilman Hans Riemer (D-At large) of Takoma Park questioned whether the workers on the scene had done a slipshod job.
“I can’t escape the notion that, did they just want to get home for the day?” Riemer asked.
Jerry Johnson, general manager of WSSC, called his workers “true professionals” who made a rare mistake in not correctly diagnosing the problem.
An observant neighbor called the original leak in to the WSSC emergency line, a move Councilmember Nancy Floreen, (D-At large) of Garrett Park, praised.
“We quite honestly rely quite heavily on the public to identify and find these kinds of situation so that we can respond,” Johnson said.
Committee Chairman Roger Berliner (D-Dist. 1) of Bethesda, asked if the utility thought the failure was part of a systemic problem or a one-time occurrence.
There was no indication that this was systemic, said a representative, but that would be clearer once an assessment was finished, which should be sometime late spring of 2014.