Miles of new tunnels to clean up Washington DC waterways - TunnelTalk
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Miles of new tunnels to clean
up Washington DC waterways
Aug 2009
Paula Wallis, Reporter
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Fig 1. Anacostia River Projects

A $2.2 billion combined sewer overflow abatement (CSO) project is moving forward to clean up and protect the waterways around Washington DC. The District of Columbia Water and Sewer Authority's (DC WASA) CSO Long Term Control Plan (LTCP), will comply with court ordered control of CSOs into the Potomac and Anacostia Rivers and Rock Creek.
Central to the program is the Anacostia River Projects, a system of 12.8 miles (20.7km) of deep level tunnels with 16 shafts, and several pumping stations and river crossings. The project is broken into four main tunneling contracts. Geographically from south to north, they are the Blue Plains Tunnel, the Anacostia River Tunnel, the Northeast Boundary Tunnel, and the Northeast Boundary Branch tunnels (Fig 1).
The Blue Plains Tunnel is planned to be design-build, and be the first into construction. RFQs (request for qualifications) is scheduled for February of next year with an approximate construction start date of May 2011. DC WASA is planning to hold two industry outreach meetings - the first set tentatively for late October 2009 - to provide detailed information to contractors and engineering firms.
At 23,600ft (7,193m), the Blue Plains Tunnel is the largest of the contracts with an estimated construction value of $300 million says Carlton Ray, Director of the CSO Long Term Control Plan for DC WASA.
Despite the plight of communities like Detroit, that have had to cancel CSO and water projects due to the collapse of user-fee funding and the absence of stimulus money to fill the void, Ray says the project is in DC WASA’s current financial plan and the Authority is dedicated to meeting the court ordered timeline (Fig 2).
“Periodic rate increases over the 20-life of construction will pay for the long term project and DC WASA is committed to meeting the completion milestones set out in the consent decree schedule,” said Ray.
JA Underground (aka Jacobs Associates) and Greeley and Hansen are program managers for the LTCP and are currently preparing the design report for the Blue Plains Tunnel, which is being planned as a design-build project.
The contract consists of 23,600ft x 23ft (7,193m x 7m) i.d. tunnel with four shafts and one diversion structure. The alignment runs 60-120ft (18.2-36.5m) under the eastern shore of the Potomac and Anacostia Rivers north from the Blue Plains treatment plant, with a smaller section running under developed land to the tunnel shaft and diversion structure at Poplar Point.
Pic 2

Fig 2. Consent decree timetable

From here the alignment runs under the Anacostia River to the Northern Portal near the new Nationals Baseball Park (Fig 3).
“The initial design work, which will include the geotechnical baseline report is ongoing and will be about 30% complete when we issue the RFQ,” said Bill Edgerton of JA Underground. “We’re not seeing a lot of technical challenges on the tunnel, however the alignment runs under a lot of US and district of Columbia government property and we will have to work very closely with various government agencies and private developers to coordinate staging and mitigate the negative impacts of construction to the surrounding communities.”
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Construction timeline

Contractors will have to operate in tight urban job sites and close to other major development and infrastructure projects. The Poplar Point working site for the Anacostia River tunnel section, for example, will share space with the South Capitol Street Bridge replacement project and the adjoining Route 295 interchange reconstruction. Other challenges will include operating without use of the active flow control systems.
The geology on the alignment of all three tunnel contracts is mostly clayey and silty soils with sandy interbeds. It is anticipated that the Northeast Boundary Tunnel and Northeast Boundary Branch Tunnels will cross sandy and silty sand with clayey and silty interbeds and basal gravely soils. Current planning includes using EPB or slurry TBM systems for excavation and bolted gasketed precast concrete linings for the tunnels. Shaft construction methods under consideration include slurry wall and ground freezing.

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Fig 3. Blue Plains Tunnel

The Anacostia River Tunnel (ART) is the second contract and has an approximate construction state date of November 2013. It will start on the southeast side of the river at the Poplar Point shaft and terminate just south of the RFK Stadium. The 12,500ft x 23ft (3,810m x 7m) i.d. tunnel will pass under Metro Green Line tunnels and under the Anacostia River threading its way amid scores of piers, piles and foundations supporting highway, railroad and riverbank retaining structures.
The third contract, with a construction state date of 2018, is the Northeast Boundary Branch Tunnels (NEBBT). These tunnels will run along R Street from a shaft near Brentwood Reservoir to 6th Steet NW, North along 1st Street NW, and North along the CSX rail facility to the Rhode Island Ave Metro Station, a total of 16,600ft (5,060m). The fourth contract, with a construction start date of 2021, is the Northeast Boundary Tunnel (NEBT).
The fourth contract, with a construction start date of 2021, is the Northeast Boundary Tunnel (NEBT). It will run 15,170ft (4,624m) from the end of the ART north under the RFK stadium parking lot, Langston Golf Course, the National Arboretum, and Mt. Olivet Road, to the Brentwood Reservoir shaft. The main purpose of NEBT and the NEBBT is to provide flooding relief to this area of the District.
The $2.2 billion CSO plan is designed to reduced combined sewer overflows by 96% overall and 98% in the Anacostia River alone.
References
Upper Rouge SCO cancelled - TunnelTalk, Jun 2009
Funding crisis cripples Detroit tunnel projects -TunnelTalk, Apr 2009
Detroit's second DRO-2 contract terminated -TunnelTalk, Apr 2009
Funding woes affect water projects in Las Vegas -TunnelTalk, Apr 2009
Detroit's first DRO-2 contract mobilization -TunnelTalk, Nov 2001
DC WASA

     

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