Bethesda Metro Stations To Close This Weekend and Three Following Weekends
Metro is piloting a waterproofing technology in leaky Red Line tunnel
A pole at the Bethesda Metro station
The Bethesda and Medical Center Metro stations will close this weekend and the three following weekends as the transit operator pilots a new waterproofing technology to attempt to fix the leaky tunnel that has caused service disruptions in recent years.
Work on the tunnel began Monday night, but this weekend will be the first when Metro closes the two stations. Shuttle buses will replace trains between the Grosvenor-Strathmore and Friendship Heights stations to allow travelers to get around the closures.
Metro contractors are using a “curtain grouting” technique used by the mining industry to install a waterproof membrane in the tunnel that stretches from Medical Center to Friendship Heights. Crews are injecting a polymer-based emulsion into holes drilled in the tunnel. The emulsion is expected to cascade down the walls and then prevent water from seeping through the concrete down to the tracks.
The leaky tunnel has been a headache for years on the Red Line, particularly in the Bethesda area. It’s the only tunnel in the system built with porous concrete that allows water to seep through and then pool on the tracks. The pooled water mixes with debris, creating a sludge that’s kicked up by passing trains. When the sludge lands on the electrified third rail, it creates electrical sparks and smoke, which Metro refers to as an arcing insulator. The transit operator single-tracks or halts service to fix the issue, causing service disruptions.
The Bethesda-area Metro stations will also be closed July 22, 23, 29 and 20 and August 5 and 6, so crews can install the waterproofing material.
If the technique works, Metro may use it in the rest of the Red Line tunnel. The Bethesda section only represents about 3 percent of the affected area of the line, according to Metro.