A smaller segment of the Red Line tracks, between Medical Center and Friendship Heights stations, also will undergo single-tracking weeknights after 9 p.m. from July 10 to Aug. 11.
Metro officials said they need extensive access to the tracks to test a new method they’re hoping will help mitigate the leaks inside tunnels that can lead to smoke and fire incidents. The technique, called “curtain grouting,” involves drilling hundreds of deep holes into the ceiling of the tunnel, and filling them with a sealant that will eventually cover the roof of the tunnel.
In a statement announcing the closures, Metro compared the process to “the way chocolate syrup cascades down an ice cream sundae.”
“Since this tunnel segment was constructed, Metro has fought a battle against Mother Nature, and Mother Nature has always had the upper hand,” said Metro General Manager Paul J. Wiedefeld said in the statement. “I want to address the water infiltration problem head on and find a sustainable solution.”
The coming weekend closures may be unpleasant news for riders who had hoped that the end of the 13-month SafeTrack repair project meant an end to scheduled closures and single-tracking.
But Metro officials say planned closures are far preferable to the kinds of unexpected, chaos-inducing problems on the tracks that can wreak havoc on a peak-period commutes and strand tens of thousands of riders.
Following are the weekends when bus shuttles will replace trains between Grosvenor-Strathmore and Friendship Heights:
• July 15-16
• July 22-23
• July 29-30
• Aug. 5-6
The tunnel leaks around Medical Center have long been recognized as a major problem. Back in 2001, a story in the Washington Post offered details on the scope of the persistent geological predicament:
The Metro subway is one of the deepest in the world, with all tunnels and underground stations at or below the water table. The water problem is most serious and getting worse along a nine-mile stretch of the Red Line from Farragut North to Medical Center in Montgomery County.
Water is eating away at the track bed, the power system, electrical components and the steel girders that support fire pipes, communications cables and power lines throughout the subway tunnels. Rail fasteners are rusting, and communications cables are corroding.
Mineral deposits left by dripping water have built up along the track bed, turning insulators into conductors and interfering with the proper flow of electricity from the 750-volt third rail to the trains.
Of Metro’s approximately 40 miles of mined subway tunnels, nine are severely wet, 18 are moderately wet and 12 are dry, Metro officials said.
The water problem, flagged by Metro as a concern as early as 1985, has accelerated at an alarming rate, according to Metro General Manager Richard A. White. The number of leaks plugged by Metro workers has ballooned from about 500 a year in the 1980s to a projected 4,600 this year.
Every month, Metro pumps about 1.25 billion gallons of water from the subways, the equivalent of 1,786 Olympic swimming pools.