DC Waters Clean Rivers Program

The Clean Rivers Project is DC Water’s 20-year, $2.7 billion effort to improve water quality in the District of Columbia. This massive infrastructure project is designed to capture and clean wastewater during rainfall before it reaches the Anacostia and Potomac Rivers and Rock Creek, and to reduce combined sewer overflows (CSOs). Components of the project also target the reduction of flooding in certain District of Columbia northeast boundary neighborhoods. The effort includes combined sewage storage tunnels as well as green infrastructure solutions to reduce total CSOs. Schnabel has worked on the project extensively since its start in 2009.

The DC Water Clean Rivers Project has combined some of the nation’s most challenging tunneling work with an aggressive schedule in a dense urban environment. DC Water’s effort to reduce CSOs relies on huge underground tunnels to store diluted sewage, which is later released to a treatment plant. These soft ground, mixed-face, and rock tunnels span over 18 miles and are 100 to 170 feet in depth. They run under the Potomac and Anacostia Rivers, military installations, National Park Land, and federal, district, and private properties.

The tunnel system also includes 22 drop shafts to carry combined sewer and stormwater flows to the tunnel level; two shafts at the tunnel terminus, which house the grit and screening removal shaft and tunnel dewatering pump station; near-surface facilities that divert flows from the combined sewers to the drop shafts; and more than a half dozen small trenchless installations.

Schnabel’s geotechnical and tunnel engineers, geologists, hydrogeologists, and environmental scientists have led various types of investigations, prepared geotechnical data and baseline reports, performed soil and water contamination assessments, and provided pump testing and hydrogeologic analysis. Our team provided automated web-based geotechnical instrumentation monitoring during the award-winning Blue Plains Tunnel construction, and during design and procurement, we were responsible for developing and maintaining the risk management effort for all 10 Division contracts. Our tasks included qualitative risk analysis and the development of registers to identify, characterize, and mitigate potential risks to each project. For the tunnel design-build contracts, we provided a probabilistic quantitative analysis of cost and schedule impacts of risk events to support budgetary contingency amounts.

Schnabel is also assisting DC Water to implement and execute the project as part of the Program Consultants Organization. Through this effort, our team provides a wide range of services, including design management and construction management for the Northeast Boundary Tunnel; structural and geotechnical design reviews for the Northeast Boundary Tunnel; preliminary and final structural design and standard specifications for the Potomac River Tunnel; and program-wide tunneling, deep excavation, and trenchless expertise. Schnabel is providing the lead tunnel engineering for the Piney Branch Tunnel Project, which is the final tunnel project for the DC Water Clean Rivers Program. The project is under design and procurement using the CMAR procurement method. For completed underground contracts, Schnabel’s personnel developed novel procurement strategies; planned and managed geotechnical investigations; established program-wide protocols for protecting third party structures; mitigated risk through design and contracting strategies; and led the development of bid documents for construction contracts for the Blue Plains Tunnel, Anacostia River Tunnel, First Street Tunnel, and Tingey Street Microtunnel Projects.