(DC Water photo)
In preparation for excavating the main shaft on Blue Plains, steel cages are assembled and lowered into pre-dug holes more than 100 ft. (30.5) below the surface. Once concrete is poured, this reinforced structure will provide stability t
A giant tunnel boring machine (TBM) known as “Lady Bird” is one of the stars in the largest construction project in Washington, D.C., since the building of the Metro System. The machine was sent underground to tunnel more than 4 mi. (6.4 km) along the Potomac at a depth of approximately 100 ft. (30.5 m).
According to District of Columbia Water and Sewer Authority, the Lady Bird was built specifically for this project in Schwanau, Germany, at the Herrenknecht Factory at a cost of $30 million. The TBM is more than 400 ft. (122 m) long and weighs more than 1,300 tons (1,179 t). A total of 26 ft. (7.9 m) in diameter and more than a football field in length when fully assembled, it will be used to dig the Blue Plains Tunnel, which is a portion of DC Water’s Clean River Project to reduce combined sewer overflows (CSOs) and improve water quality in D.C.
Approximately one-third of D.C. has a combined sewer system. Overflows occur during heavy rain when the mixture of sewage and storm water cannot be contained in the pipes, causing it to overflow to the nearest water body. DC Water’s plan to significantly reduce CSOs to the Anacostia River is to build massive underground tunnels that will store the combined sewage and runoff when necessary, then slowly release it when the system has the capacity to treat it. Similar tunnels are used in cities such as Chicago, Indianapolis and Atlanta.
The Lady Bird will be used to dig the first portion, known as the Blue Plains Tunnel, a 4-mi. section of the 13-mi. (21 km) Anacostia River Tunnel. Starting from two deep shafts at Blue Plains, the Lady Bird will tunnel 24,200 linear ft. (7,376 m) up the Potomac River and the Anacostia River, creating a metro-sized tunnel. This tunnel will be instrumental in DC Water’s effort to reduce nutrient pollution to the Potomac River and Chesapeake Bay.
TBMs are named and christened just like boats are. The name Lady Bird was chosen for DC Water’s TBM after Claudia Alta “Lady Bird” Johnson.
“When her husband became president in 1964, she made it her mission to preserve and protect the environment,” a spokesperson said. “In 1964, she formed ’The Committee for a new Beautiful Capital,’ whose positive contributions are still visible today. She encouraged her husband to declare the Potomac River ’a national disgrace,’ which drew attention to the declining health of America’s waterways and was a catalyst for the eventual Clean Water Act of 1972.”
The cutterhead for the Lady Bird was christened with D.C. tap water during an April 9 ceremony involving District of Columbia Mayor Vincent C. Gray.
The total length of the Lady Bird is 442.9 ft. (135 m), which is the equivalent of one and one-quarter football fields including end zones. It weighs 1,323 tons (the equivalent of approximately seven and one half Boeing 747s).
The cutterhead diameter is 26 ft. 4 in. At full production, the Lady Bird is reportedly capable of tunneling up to 100 ft. (30.5 m) per day. It is expected to average 70 to 80 ft. (21 to 24 m) per day.
It will move approximately 13 million cu. ft. (368,119 sq m) of soil for this project. To remove the dirt from Blue Plains, it will require three dump truck loads for every one foot of tunnel advancement. Over the entire length of the tunnel, this will result in more than 72,500 truckloads.
The machine was delivered in pieces and was lifted one piece at a time and lowered into the shaft, then assembled at the bottom. The crawler crane needed to lift the heaviest pieces was a 660-ton (598 t) capacity lattice boom crawler crane with a jib extension.
A spokesperson noted that the TBM will initially launch with the first six of nine trailing gear gantries. In this configuration, the TBM has all the basic utilities needed to begin tunneling. The excavated dirt will be delivered to a muck box at the back of the TBM and lifted out with a crane. As the TBM advances forward, the remaining sections will be added in-line one at a time. After the entire TBM has exited the launch shaft, the shaft will be fitted with muck handling equipment and the full-scale tunneling operation can begin.
Clean Rivers Project
The Clean Rivers Project’s purpose is to reduce combined sewer overflows to the District’s waterways — the Anacostia River, the Potomac River, and Rock Creek. It will cost approximately $2.6 billion and is scheduled for completion in 2025.
Plans are to reduce CSOs to the Anacostia River by 98 percent and to all three water bodies by 96 percent overall.
According to DC Water, the project is starting with the most impaired water body, the Anacostia River, which is slow-moving and shallow. The 13-mi. tunnel system for the Anacostia is broken into three segments. The tunnel system ends at Blue Plains Advanced Wastewater Treatment Plant, where the combined sewage will be treated before being discharged back to the Potomac River. Construction and tunneling are beginning at the end of the tunnels at Blue Plains and moving upstream, resulting in the lower portion being operational before the entire tunnel is built.
Anacostia River Tunnel
The Anacostia River Tunnel project will extend from Robert F Kennedy Stadium in northeast D.C. to the Poplar Point Pumping Station in southeast D.C. It will be approximately 12,500 ft. (3,810 m) in length, 23 ft. (7 m) in diameter, and approximately 100 ft. (30.5 m) underground.
It will include six shafts to serve as access points for the tunnel and to assist in discharging CSOs to the Anacostia River, with diameters varying from 30 ft. (9 m) to 75 ft. (23 m). Two diversion chambers also will be installed along the tunnel, and there will be odor control vaults at four locations.
Construction is estimated to begin in November 2013 and be complete in January 2018.
Blue Plains Tunnel
The Blue Plains Tunnel project extends from the Blue Plains Advanced Wastewater Treatment Plant (BPAWWTP) in southwest D.C. to the Main Pumping Station in southeast D.C. It will include the installation of 24,300 linear ft. (7,407 m) of tunnel within the project area, the construction of a 132-ft. (40 m) diameter dewatering shaft and a 76-ft. (23 m) diameter screening shaft at BPAWWTP to serve as the main access point for the Blue Plains Tunnel construction.
In addition, the contract calls for construction of a 55-ft. (17 m) diameter drop shaft at the Main Pumping Station to serve as the terminus point for the Blue Plains Tunnel construction, the construction of a 50-ft. (15 m) diameter drop/overflow shaft at Joint Base Anacostia Bolling, and the construction of a 55-ft. (17 m) diameter junction/drop shaft at Poplar Point Pumping Station.
Construction was expected to continue from July 2011 through November 2015.
This portion of the project is located at Robert F. Kennedy Stadium drive in northeast D.C. It involves the construction of a diversion structure to divert CSOs out of the existing Northeast Boundary Trunk Sewer and convey it to the future tunnel system. It also calls for the construction of an overflow structure to provide flood relief to the northeast boundary and discharge CSOs to the Anacostia River.
The schedule for this portion was Sept. 2011 to Aug. 2013.
CSOs 015, 016
This portion of the project is on M Street SE, between 9th Street SE and 14th Street SE. It calls for CSOs to be diverted from existing combined sewers using three diversion chambers, then conveyed to the future tunnel system along M Street SE through a series of 48-in. (122 cm) and 108-in. (274 cm) diameter diversion sewers constructed using trenchless methods. CSOs totaling 695 million gal. (2.6 billion L) per day will be delivered to the LTCP tunnel system. The work also includes the rehabilitation of selected portions of the Eastside Interceptor (ESI) sewer and the Southeast Relief Water Main (SRWM).
The timeline for this portion is April 2012 to March 2014.
Main Pumping Station, Tingey
This portion calls for the installation of 1,200 linear ft. (366 m) of combined sewers on Tingey Street between 2nd and 5th Streets. In addition, it includes the construction of air handling facilities within a 55-ft. (17 m) diameter concrete shaft to serve as both access and terminus points for the Blue Plains Tunnel. Four diversion chambers along the Tingey Street sewer will carry CSOs into the tunnel.
The timeline for this portion is Sept. 2013 to Aug. 2017.
Northeast Boundary, Branch Tunnels
This portion is located from Kennedy Stadium to the Rhode Island Avenue Metro Station, and then along Rhode Island Avenue to 6th St. NW. It will provide additional storage for CSOs and will relieve street and basement flooding in the Northeast Boundary area.
The contract calls for installation of approximately 26,600 ft. (8,108 m) of tunnel and the construction of drop shafts and diversion chambers along the tunnel.
Field investigation will continue through December 2013, and tunnel construction will occur from 2018 to 2022.
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