Rehabilitation of Boston Harbor Tunnel – The “Quarter Duct” Solution

Structural rehabilitation of the Sumner Tunnel under Boston Harbor will be finalised in late 2024. Associated with the structural work, the in-tunnel parts of the ventilation system had to be re-constructed. Conceived as a structural project, the base requirement was for the reconstructed ventilation to be no worse than existing. However, reconstructing the 1930s scheme carried significant schedule risk and uncertainty in the ability to achieve the Owner’s Quality requirements. In addition, it would have missed an opportunity to dramatically improve the smoke management. Working within strict project constraints, an innovative reimagining of the ventilation ducts’ operation improved smoke control performance using existing ventilation plant capabilities, and with only a quarter of the previous duct being rebuilt. Testing of the ventilation system before and after rehabilitation qualitatively and quantitatively demonstrated the improvements made to the smoke management. Insights from the iterative concept development, and details of the testing procedure are provided. An innovative Ventilation Test Vehicle was used to perform environmentally friendly warm smoke tests with very little demand on tunnel closure time. The ventilation concept dramatically improved fire safety, minimised change to pre-existing operations, and saved construction time, and tunnel closure time.