Metro reminds customers of Red Line service changes over next four weekends due to leak mitigation pilot
Metro will temporarily close a five-mile segment of the Red Line this weekend -- and the three weekends that follow -- to advance a project that will test the effectiveness of a new waterproofing technique that could reduce water from entering the deep tunnels and affecting service reliability.
On Saturday and Sunday, Red Line trains will be replaced with free shuttle buses between Grosvenor and Friendship Heights stations.
As part of the pilot, which began with overnight work this week, Metro's contractor is drilling hundreds of holes in the ceiling of the existing Red Line tunnel until the exterior of the tunnel is reached. From there, a proprietary polymer-based emulsion (PBE) grout is being injected into each hole at high pressure, which cascades down the curved exterior of the tunnel (like the way chocolate syrup cascades down an ice cream sundae). The injected material forms a rubberlike impenetrable membrane, or "curtain," between the exterior of the tunnel wall and the surrounding ground medium.
For the next four weekends, Red Line service will be replaced by free shuttle buses between Grosvenor and Friendship Heights stations. Trains will operate at regular weekend intervals outside the work area. However, customers traveling through the work zone (using shuttle buses) should allow up to 30 minutes of additional travel time.
The deep tunnel segment of the Red Line between Dupont Circle and Grosvenor was actually designed to leak because it was constructed prior to more modern tunneling techniques that include a waterproof membrane. The tunnel is well below the groundwater table and under high hydrostatic pressure, resulting in water entering the tunnel in thousands of locations. However, the presence of water/moisture contributes to higher incidences of arcing insulators in this area and accelerates corrosion of the track bed, rails, fasteners, cables and other components that require more frequent replacement. Metro estimates that two thirds of all arcing incidents occur along this segment of the system.
"Just as we have addressed the root causes of track infrastructure problems and railcar reliability issues, I want to address the water infiltration problem head on and find a sustainable solution. Our Red Line riders deserve nothing less," Wiedefeld said.
The pilot will be evaluated during the autumn season when water infiltration poses a greater challenge.
For more information
Original News Release: Metro to test new waterproofing of Red Line tunnels