Metro Red Line waterproofing pilot to be expanded amid signs of improvement
Metro today announced that a water leak mitigation project on the Red Line will be expanded. Early results from the pilot, which began in July, shows the installation of a new waterproofing membrane outside the Red Line tunnel is reducing water infiltration in two test segments.
Work by Metro and its contractor will continue on an additional 4,000 foot-section of inbound track between Medical Center and Grosvenor that will triple the area of deep tunnel segment under the pilot from the initial scope.
The leak mitigation pilot is testing the use of a "curtain grouting" technique in which a proprietary polymer-based material is injected through holes drilled into the tunnel ceiling to form a waterproof membrane on the exterior of the tunnel walls.
In the two test segments – a 2,000-foot section of inbound track between Medical Center and Bethesda and the entire Medical Center interlocking – the tunnels have remained relatively dry, even with excessive rains in late July and August that brought up to more than three inches of precipitation in one day.
The deep tunnel segment of the Red Line between Dupont Circle and Grosvenor was constructed prior to widespread use of NATM, the New Austrian Tunneling Method, which provides tunnels with a waterproof membrane. The area is well below the water table and subject to high hydrostatic pressure that makes it prone to water infiltration that more quickly corrodes track infrastructure.
Injecting the curtain grouting requires drilling hundreds of holes through the tunnel ceiling and can only be done when trains are not running. The expanded scope of the project will require approximately six weeks, including two weekend shutdowns where buses will replace trains through the area.
In order to safely and effectively continue the pilot, Metro is announcing the following service changes:
On weeknights from October 16 through November 22, Red Line trains will single track between Medical Center and Grosvenor starting at 9 p.m. Minor delays are expected.
Free shuttle buses will replace Red Line trains between Medical Center and Grosvenor stations on the following two weekends:
- Saturday and Sunday, October 28, 29
- Saturday and Sunday, November 18, 19
In addition, Red Line trains will single track between Medical Center and Grosvenor on the following two weekends:
- Saturday and Sunday, October 21, 22
- Saturday and Sunday, November 11, 12
Finally, Red Line trains will single track between Medical Center and Twinbrook to accommodate other track work on the following weekend:
- Saturday and Sunday, November 4, 5