CSO 19 Shaft Cradle | Washington, D.C.

Safe Formwork that Reduces Time and Labor Costs

Washington, D.C.

Tunnel to Alleviate Flooding

The Clean Rivers Project is DC (District of Columbia) Water’s ongoing program to reduce combined sewer overflows (CSOs) into the district’s waterways. The Northeast Boundary Tunnel project is one of five initiatives they have launched to clean up the Anacostia and Potomac Rivers. This project promises to alleviate flooding-related economic losses, basement backups, and sewer overflow discharge into the Anacostia River. Construction of the tunnel will decrease the costs and risks associated with flooding in the area.

Construction of a 5-mile-long (8-Km-long) Tunnel

The Northeast Boundary Tunnel (NEBT) is approximately five miles (8 Km) long and connects to existing sewer pipes throughout the city. During heavy rainfall, the tunnel will capture and temporarily hold stormwater and sewage overflow, preventing it from overwhelming the sewer system and discharging into local waterways. Once the rain subsides, the captured water and sewage will be gradually released to a wastewater treatment plant for processing.

Partner of Choice for tunnel formwork

Over the past five years, Salini Impreglio/Healy JV and EFCO have partnered and collaborated on many initiatives. Recently, Salini Impreglio/Healy JV contacted EFCO to provide a solution for forming the floor slab of CSO 19 Shaft, which includes the bottom 180° half of a 28′ (8.5 m) diameter tunnel profile.

EFCO Formwork Solution

At the location of the NEBT project, the profile across the shaft is 9′ (2.7 m) deep. The formwork solution must be kept suspended 6′ (1.8 m) above the ground before and during concrete placement.

Safe Formwork Time and Labor Costs

EFCO created a support structure with the REDI-RADIUS® formwork system and SUPER STUD® Trusses, which allowed it to be put together at the ground level and then lowered into the shaft in sections. This helped the Salini Impreglio/Healy JV team save on labor costs and assembly time. Assembling the formwork in larger, open areas with a crane instead of inside the tunnel provided the contractor with the lowest in-place concrete cost benefit. The large formwork panels of the system decreased the crane time needed for assembly/disassembly, and the SUPER STUD frame provided a way to suspend the REDI-RADIUS panels in addition to providing a platform to work from while placing concrete.

Why Choose Anyone Else?

The collaboration between Salini Impreglio/Healy JV and EFCO on this project yielded another in a series of wins for the 5-year partnership, as the work was completed rapidly and without any issues.