Dramatically reducing combined sewer overflows into the District of Columbia’s waterways, the Clean Rivers Project is DC Water’s 20-year, $2.7 billion effort to improve water quality. This massive infrastructure project is designed to capture and clean wastewater during rainfalls before it reaches the Anacostia and Potomac Rivers and Rock Creek. Schnabel has worked on the project since its start in 2009.

The District of Columbia Water and Sewer Authority’s (DC Water) effort to reduce combined sewer overflows (CSOs) – a mixture of raw sewage and rainwater – uses huge underground tunnels to store the diluted sewage, which is later released to a treatment plant. When completed, there will be more than 12 miles of 23-foot diameter storage and conveyance tunnels, associated shafts, pump stations, overflow facilities, and diversion chambers in Wards 5, 6, 7, and 8.

The first three major design-build contracts – the Blue Plains Tunnel, the 1st Street Tunnel, and the Anacostia River Tunnel – are finished. The largest and longest remaining design-build contract, the Northeast Boundary Tunnel, is under construction, with completion scheduled for 2023.

Our 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. We also provided automated web-based geotechnical instrumentation monitoring during the award-winning Blue Plains Tunnel construction.

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 development of registers to identify, characterize, and mitigate potential risks to each project. For the tunnel design-build contracts, we also provided a probabilistic quantitative analysis of cost and schedule impacts of risk events to support budgetary contingency amounts.

Photo: Courtesy of DC Water