Challenges for Design and Constructability of Tunnel Dewatering Pump Stations

The District of Columbia Water and Sewer Authority is implementing a consent decree driven long-term control plan aimed at reducing combined sewer overflows into the District's waterways. This plan includes several capital projects implementing a network of tunnels leading to a tunnel dewatering pump station and enhanced clarification facility to pump and treat storm water and sewer overflows collected and conveyed by the tunnel system. The deep pump station posed significant challenges in terms of design and constructability. This paper focuses on the technical elements, challenges, lessons learned and significance to other similar deep pump station projects.