Anacostia River Tunnel Project DC Water

DC Water


Tunnel Design and Site Support Services:

The Anacostia River Tunnel project is designed to capture and provide storage for combined sewer overflows (CSOs) being discharged to the Anacostia River. The project consists of a system of deep large diameter underground storage tunnels and associated diversion and pumping facilities. When completed, the tunnel system will be used for the conveyance and storage of combined sewage overflow. The tunnel system consists of a series of three tunnels from Blue Plains advanced wastewater treatment plant to the north east boundary area in the vicinity of Brentwood Reservoir.

Gall Zeidler Consultants (GZ) designed the Inter Shaft Connector Tunnel (ISCT) between CSO 019 North and South shafts, which are part of the Division C – CSO 019 Combined Sewer Overflow and Diversion Structures.

The ISCT has a diameter of approximately 27.3 ft (8.3 meters) and is located approximately 99 feet (30.2 meters) below ground level in clayey soil of Patapsco/ Arundel Formation. The maximum and minimum groundwater level varies between 1 foot (0.3 meters) and 5 feet (1.5 meters) below ground surface.

The scope of the design services GZ provided for the ISCT included the design of the excavation and support system, the final lining, and the waterproofing system. The excavation and support design of the tunnel was based on Sequential Excavation Method (SEM) principles. GZ also provided expert design consulting services and is currently providing full site support during construction.


Washington, D.C. USA
2012– Present
Mined Tunnel (TBM, SEM)
102 feet (31 meters)
27 feet 4 inches ( 8.3 meters) at the Springline
Clay of the Patapsco / Arundel Formation
Approximately $1.6 Billion
Impregilo, Hailey, and Parsons (IHP)
DC Water