First Street Tunnel

During a storm event, the First Street Tunnel will store more than 8 million gallons of combined sewer overflow in its 2,700-foot-long, four-shaft tunnel, preventing flooding in Bloomingdale and Le Droit Park.


Location

  • Washington, DC, USA

Sector

Service

  • Shaft Design and Construction
  • Tunnels Structural Engineering
  • Rock Tunneling
  • (View all)

Client

  • DC Water

Project Status

  • Completed in 2016


New CSO Tunnel Prevents Flooding After Storm

The First Street Tunnel (FST) is a storm water storage tunnel that was constructed, using a tunnel boring machine (TBM). This portion of DC Water’s Clean Rivers Project extends along First Street NW, beginning at the McMillan Sand Filter site and travelling south along First Street to Rhode Island Ave NW. During a storm event, the First Street Tunnel will store up to 8 million gallons of combined sewer overflow (CSO) in its 2,800 feet of tunnel and four shafts. It will utilize a pump station located at Rhode Island Avenue to pump storm water back to the shallow sewer system, once the storm has subsided.

Key Numbers

Length
.5 miles
Shafts
4
Shaft depth
54 yards

First Street Tunnel tbm in Launch Shaft

Innovative Engineering

Construction was completed successfully, thanks to a collaborative effort between the Owner (DC Water), Owner’s Engineers (McMillan Jacobs Associates, Greeley and Hansen), and Design-Builder (Skanska, Jay-Dee, WSP). Currently operational, the project will feed into a larger sewer system serving Washington, DC once the Northeast Boundary Tunnel (NEBT) is completed in 2022.

The use of a centralized freeze plant to construct support of excavations for shafts, adits, and adit to tunnel junctions was a first. A utility trench was constructed along a back alley to provide brine supply to the three satellite sites.

This was one of the first uses of steel fiber reinforced precast tunnel liners on the East Coast of the US.