Lining the Line

by Walter Mergelsberg, Deputy Assistant General Manager of Design and Construction; Washington Metropolitan Area Transit Authority, Washington, D.C.,
Vojtech Gall, Vice-President; Dr. G. Sauer Corp., Herndon, VA,
Gerhard Sauer, President; Dr. G. Sauer Companies of Salzburg, Austria; London; Herndon, VA,


Serial Information: Civil Engineering—ASCE, 1996, Vol. 66, Issue 3, Pg. 50-52


Document Type: Feature article

Abstract:

Having succeeded in achieving dry stations and tunnels in mined construction, flexible waterproofing membranes are now being used to waterproof cut-and-cover subway stations and old, leaking tunnels. In the early 1980s the Washington Metropolitan Area Transit Authority (WMATA) approved a value engineering cost proposal (VECP) for the construction of its Section B10, Wheaton Station. The (VECP) relied on the New Austrian Tunneling Method and on the economic approach of the concept-promised cost savings. The selling point, finally, was the proposed waterproofing system involving flexible, plastic membranes. More than 10 years after construction, the Wheaton Station and running tunnels remain completely dry, creating a comfortable space for Metro's patrons and an untroubled environment for the operations and maintenance staff. Since its success in Washington, this waterproofing system has been adopted for many highway tunnels and subway structures. With the extension of Metro's Redline to the north and construction of its Mid-City E-route, WMATA is again pioneering the field of waterproofing in the U.S. by applying a flexible, plastic membrane to waterproof cut-and-cover structures. The Glenmont, Georgia Avenue-Petworth and Columbia Heights stations will also use this waterproofing system. The Glenmont, with an average excavation depth of 50 ft, uses the open system with sidewall drains. The Mid-City E-route, however, will rely on the closed system by wrapping the entire structure in the membrane.

Subject Headings: Tunnels | Subways | Membranes | Construction management | Value engineering | Synthetic materials | Railroad stations

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