Metro said it is seeing evidence the $12.2 million it spent to prevent water leakage in its Red Line tunnels was successful.
Metro officials are putting together a possible contract for construction on the northeastern end of the Red Line, between Forest Glen and Silver Spring stations, to use similar methods to conduct water-related tunnel repairs in 2019.
To riders, torrential rain resulting in smoke and fire incidents is a perennial irony of the Metro system. But from an electrical engineering standpoint, it makes sense. Water and electricity don’t mix. (Think of a hair dryer dropped into a bathtub full of water.) When rain leaks into the tunnels, particularly in the more porous sections of the system, standing water on the tracks can cause smoldering from the electrified third rail.
In fact, water infiltration is one of the most frequent problems flagged by inspectors from the Federal Transit Administration, who walk the tracks daily to mark defects and areas for improvement.
In FTA’s recent publicly available report, inspectors note dozens of incidents where water is leaking into the tunnels and causing damage.
At one spot, on the tracks on the southeastern end of the Green Line, “a tunnel leak was observed over the catwalk with buildup of sediment, mud, and water running through an open electrical box creating an electrical hazard,” FTA inspectors wrote. In another, on the southern end of the Yellow Line, “a side wall tunnel leak was observed . . . allowing water to strike the third rail, the running rail, and the fastening system, and causing corrosion.”
When heavy rain inundates the system, the precipitation is typically followed by a significant uptick in arcing incidents, which a Metro spokesman described as “snap, crackle, pop.”
The phenomenon was clearly in play in July 2017, when the Washington region experienced 9.15 inches of rain in one month, the rainiest July in decades. That month, Metro logged 15 fires — more than double the monthly average of fires in that fiscal year, which was 6.8. Nine of those were arcing incidents, the most common type of fire resulting from water.
One year later, things changed — at least somewhat.
July 2018 was another wet month for the region with 9.7 inches of rain, according to the National Weather Service.
Yet, there was no correlating spike in track fires; six arcing incidents were recorded. That’s far from perfect, but not the level seen during rainy months the previous year.
In fact, according to Metro’s statistics, the rolling accumulation of annual fires decreased by 37 percent from last year to this year.
In the year preceding July 2017, Metro logged 63 arcing incidents. Between July 2017 and this July, there were 40, according to Metro’s latest statistics — a modest improvement.
The Montgomery County Fire Department in Maryland noticed the improvement. Pete Piringer, spokesman for the fire department, said firefighters are not being called quite as often to check on reported smoke or fires at Metro stations.
“Frequency has been a bit less than it was in the past,” Piringer said.
More specifically, he said, during the rainy spell at the end of August, there was only one fire on the stretch of tracks between the Grosvenor-Strathmore and Friendship Heights stations — a spot that usually has multiple fires during any period of intense rain.
Metro isn’t raising the victory flag yet. Fires of all kinds are still a major problem. From fiscal year 2017 to fiscal year 2018, the total number of fires involving high-voltage cables — the most serious type of fire that happens on the system — grew from two to five.
Even so, Metro officials are cautiously optimistic that they’re beginning to make long-term changes that prevent fires. They say curtailed late-night service hours and extended maintenance windows when workers can clear the tracks have made the system less vulnerable to flames, as well as the recent multimillion-dollar project to plug holes on the northwestern end of the Red Line tunnel.
“It’s so many things we’re doing to try to minimize the potential for that — the leakage mitigation on the Red Line . . . the extra hours that we have to maintain the system, where we can get out there to clean the drains and things like that,” Metro General Manager Paul J. Wiedefeld said. “It’s very important. So, overall, yes, the trend is moving that way.”
The tunnel leak mitigation project was conducted last year on the northwestern segment of the Red Line near Medical Center station, the most leak-prone section of tunnel in the whole Metro system.
According to data from the Montgomery County Fire Department, between January 2014 and July 2017, there were 46 fires at Medical Center station — the most recorded by any local fire department of any station in the system. The next most fire-prone station was just one stop away, at Bethesda, with 41 recorded fires in a 3.5-year period. The third-highest number of fires occurred down the line at Friendship Heights station.
Metro tried a new, costly sealing method from recent innovations in the mining industry to help seal off inflows of groundwater.
The complicated process involves drilling hundreds of holes in the tunnel’s ceiling, then pumping those holes full of a special sealant that acts as a waterproof membrane.
According to Metro, the substance drips down the holes “the way chocolate syrup cascades down an ice cream sundae” and covers the ceiling, stopping leaks in the concrete from trickling (or gushing) onto the tracks.
Metro spokesman Dan Stessel said the transit agency is “encouraged by the positive results we’ve seen to date.” They might utilize more of the method in the future.
“We are currently putting a contract together for the purposes of addressing the second-worst segment, which is on the other side of the Red Line between the tunnel portal outside Silver Spring to Forest Glen station, again on both tracks,” Stessel said. “We expect that work to occur next year.”
Other areas of the system could receive a similar treatment in the future.
“Our goal is to tackle these areas in order of severity,” Stessel said.