Waterproofing

The Washington Metropolitan Transit Authority (WMATA) faces serious problems related to water intrusion in sections of the Red Line. Especially in the Northwestern Section water leakage by far exceeds the acceptable limits. The consequences include electrical malfunctions, icing and clogging of the drainage system as well as deterioration of the tracks and the utilities in the tunnels. They are detrimental to an efficient operation and represent considerable safety hazards. The report describes a permanent, none adhesive waterproofing layer system for the rehabilitation of the WMATA Red Line tunnels and underground structures. It shows the feasibility and constructibility of the selected approach for a single tunnel and shaft, similar solutions will be developed for adits, crossovers, etc.

Glenmont, MD is a suburban community located approximately 12 miles north of Washington, DC. The Glenmont Station is located beneath Layhill Road north of Georgia Avenue and features a center paltform and an arch architecture. The Tunnel alignment runs along Georgia Avenue, a busy street flanked by shopping centers and private homes, and connects the Weathon Station with the Glenmont station. Four ground categories and support classes were developed according to the prevalent geology. The contract allowed for changes to the support elements with the engineer's approval and modifications to the ground support categories were made based upon observations of the ground behavior and the initial lining. Monitoring was performed with a variety of instruments (convergence bolts, inclinometers, extensometers, pressures cells, etc). The tunnel waterproofing system is an integral part of the project design and comprises a PVC membrane on a non-woven geotextile over the whole section from side drain to side drain. This system has ensured a dry Tunnel and Station and provided the owner with low maintenance costs.

Leak remediation measures at the East and West Connector to the Mezzanine Level of City Place Station. Measures consistend of joint and crack grouting, the installation of a felxible membrane lining on the structural concrete lining and a cleaning of the existing drainage system.