Finding a Solution: Skanska USA Provides Relief to Washington D.C. Neighborhoods with a Brokk 400

Torrential rain. Sewer-filled street. Submerged vehicles. That’s only a fraction of the issues that have distressed two neighborhoods in Washington D.C. And now, after nearly a century of tremendous flooding, the neighborhoods of Bloomingdale and LeDroit Park can see the light at the end of the tunnel — the First Street Tunnel.

The $157 million tunneling project is a portion of DC Water’s Clean River Project and is supported by the DC Water Board in an effort to reduce combined sewer overflows, improve water quality and support flood protection in the District of Columbia.

The project consists of a 21-foot-diameter tunnel that will store up to 8 million gallons of storm water — that equates to as much as 12 Olympic-sized swimming pools. Storm water is held in the tunnel during rainstorms and pumped back into the sewer system once the storms subside. This alleviates sewer backups, overland flooding and most importantly, decreases water pollution.

While the First Street Tunnel is part of a larger project, it will immediately provide relief to the affected neighborhoods of D.C. That’s where Skanska USA came in. Skanska — a construction and development contractor headquartered in New York — won the design-build contract on the First Street Tunnel project in October of 2013 as a joint venture with Jay Dee Contractors. To construct the shafts efficiently and effectively Skanska would need to rely on equipment that was compact and versatile, which is why they turned to Brokk.

During the excavation of a 26.5-foot-diameter, 85-foot-deep shaft, August Scalici, Brokk field sales application expert, demonstrated the Brokk 400. Skanska crewmembers watched as it swiftly excavated the shaft in less than three hours. They were sold.

“After seeing the demonstration we knew the Brokk 400 was the perfect fit for the project,” said William Bracken, SEM project manager at Skanska. “It’s aggressive enough to complete the demolition work, yet performs the delicate work, too.”

With the Brokk 400 by its side, Skanska began digging a 2,700-foot-long tunnel with four diversion chambers, drop shafts and pumping stations to discharge the stored water to the Blue Plains Wastewater Treatment Plant. For the excavation Skanska deployed a frozen ground system with three chiller units— an effective method to avoid the removal of ground water. This system super cools the water in the soil by circulating chilled liquid brine through small pipes. With the system in place, Skanska used the Brokk 400 to chisel away the frozen ground — in a fraction of the time of alternative methods.

“Ultimately, the Brokk 400 provided us with un-matched efficiency thanks to its compact size, breaking ability and versatility,” Bracken said. “We were beyond impressed with its accuracy and precision with getting the appropriate radius’ when removing the materials and its easy positioning within the shaft.”

With the help of the Brokk 400, Skanska and its crew finished the shaft construction on schedule. While the shaft sinking is complete, there is still more that lies ahead, but for now, the communities of Bloomingdale and LeDetroit can rest easy as they fear floods no more, thanks to the efforts of DC Water, Skanska and JayDee Contractors. The First Street Tunnel construction is scheduled to be completed by the spring of 2016.