Mining is now complete on the Washington Suburban Sanitary Commission’s (WSSC) 5.3-mile (8.5km) long Bi-County Water Tunnel project, located in the Maryland suburbs immediately north of Washington DC.
Following numerous challenges – including high water inflows at shaft locations, areas of poor rock quality and a major TBM breakdown – the Oscar Renda Contracting, Southland Contracting and SAK joint venture (RSS JV), achieved the final hole through with its 10ft (3m) diameter re-furbished Robbins Main Beam TBM at 2.30pm on Friday, April 26.
The WSSC provides water and wastewater services to 1.8 million customers in the Prince George and Montgomery Counties, in Maryland. Conceived more than 20 years ago, the Bi-County Water Tunnel will increase supplies of clean drinking water to eastern areas of two counties in Maryland and also Washington DC. The increased water supply will alleviate current capacity limitations, and the tunnel will also serve as an additional high-pressure water source during peak-use periods, droughts, and emergencies.
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WSSC hired Black & Veatch to design the tunnel and its valve vault structures. In August 2009, the $113 million construction contract was awarded to RSS JV. A joint venture of Jacobs Associates and Louis Berger Water Services is providing construction management. Project completion is currently anticipated in Spring 2014.
For a full report on the project and the challenges encountered during construction, see NATJ’s April/May 2013 digital edition.