WASHINGTON, D.C.—The District of Columbia Water and Sewer Authority (DC WASA) selected Jacobs Associates as General Consultant for Tunnels and Geotechnical Engineering (GCTGE) for its Long-Term Control Plan (LTCP). The purpose of the LTCP is to reduce combined sewer overflows to the Anacostia and Potomac Rivers and Rock Creek, and to decrease surface flooding during major rain events in the northeast boundary neighborhood of the District of Columbia.
DC WASA distributes drinking water throughout the nation’s capital, in addition to collecting and treating sewage in Washington, D.C., and several counties in Maryland and Virginia. It is a unique agency in that it operates the largest advanced wastewater treatment plant in the world, treating more than 1 billion gallons per day during peak flows.
The Jacobs Associates—led team includes URS Corporation as the main subconsultant, along with Schnabel Engineering. Both are key members of the group of 12 subconsultants. DC WASA will combine this team and the recently selected Program Manager team, led by Greeley and Hansen into one group of Program Consultants. This consolidated Program Consultant team will assist DC WASA to deliver the LTCP by providing planning, exploration, engineering, design, and construction-related services.
The LTCP has a strict schedule, with design beginning in March 2009 and construction slated for 2011. This timeline requires start-up of the River Area tunnels in 2018 and the Northeast Boundary tunnels in 2025. Overall, there are four tunnel systems comprising 13 miles of storage and conveyance conduits ranging in diameter from 15 to 23 feet, all of which will be constructed in the Potomac formation’s soft clays and sands. The system will provide a total storage capacity of 157 million gallons. In addition to the tunnels, a major component of the underground work for this program is construction of 17 large-diameter, deep shafts that will be used to convey and deaerate consolidated combined sewer flows to the tunnels, which are planned to be between 70 and 120 feet deep.