Friday, September 29, 2017

WMATA expands waterproofing after pilot success

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WMATA expands waterproofing after pilot success WMATA

Washington Metropolitan Area Transit Authority (WMATA) is expanding a water leak mitigation project on its Red Line after positive early results from the pilot project that began in July.

The pilot project consisted of a test of the use of a "curtain grouting" technique to add a waterproof membrane to the exterior of the tunnel walls using a proprietary polymer-based material.

WMATA and its contractor say the transit agency plants to continue the process 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.

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.

WMATA notes that the deep tunnel segment of the Red Line between Dupont Circle and Grosvenor was constructed prior to widespread use of 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.