Bouygues Construction wins $819 million contract for Potomac River sewer control tunnel in D.C.
(UI) — DC Water has issued notice to proceed to the CBNA-Halmar Clean Rivers Joint Venture comprising CBNA (a U.S.-based subsidiary of Bouygues Construction) and Halmar International for the design-build contract for the Potomac River Tunnel.
This is a major environmental project designed to control combined sewer overflows and to improve water quality in the Potomac River in Washington D.C. The contract value is $819 million.
The purpose of this project is to collect and store combined sewer system discharges and stormwater run-off during storm events that exceed the capacity of the combined sewer system along the Potomac River in the District and convey them to DC Water’s Advanced Wastewater Treatment Plant at Blue Plains. The project will increase the capacity of the sewer system using deep storage tunnels and will significantly decrease CSO overflow events impacting the Potomac River, the fourth-largest river along the U.S. East Coast.
The main tunnel, which is 5.5 miles (8.9 km) long and approximately 100 feet (30 m) deep with internal diameter of 18 feet (5.5 meters), will cross variable geological conditions (clay, alluvium, hard rock) and will pass close to Washington D.C's iconic monuments. It will require the use of two tunnel boring machines (TBM) customized specifically for these soil conditions. Ancillary structures comprise of 9 shafts, adits connecting to the main tunnel, and near surface structures which link the new infrastructure to the existing sewage system.
Works on the project are expected to start end of 2023 with a construction duration of almost 6 years. It is expected to employ 400 people at peak times, with a strong commitment to local employment and integration of local and disadvantaged businesses.
The CBNA-Halmar Clean Rivers JV will be supported by leading engineering companies COWI and Hatch to carry out the design and is committed to completing this important project through a sustainable delivery approach.
Bouygues Travaux Publics is already building a tunnel in Pawtucket (Rhode Island, USA) to store rainwater and sewer overflows, as part of a program to improve water quality in Narragansett Bay.
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