Long Term Control Plan Combined Sewer Overflow Control Program
District of Columbia Water and Sewer Authority (DC WASA), in coordination with the National Park Service (NPS), propose to initiate Anacostia River Projects (ARPs) in order to reduce the number of combined sewer overflow (CSO) events. CSOs occur when the capacity of the combined sewer system is exceeded during storm events. As a result, the excess flow, which is a mixture of sewage and storm water runoff, is discharged directly to the Anacostia River without treatment. The ARPs are part of the District's overall Long Term Control Plan (LTCP) to reduce CSOs to the Anacostia River, Potomac River and Rock Creek.
A broad range of alternative technologies to control CSOs were considered in developing the LTCP. These included source controls, inflow controls, sewer system optimization, sewer separation, storage technologies, treatment technologies, and receiving water improvements. Through analysis of individual technologies and various combinations of technologies, DC WASA determined that a deep tunnel system to provide storage capacity for CSO diversions and convey the excess CSO volume to the Blue Plains Advanced Wastewater Treatment Plant (BPAWWTP) through pumps and gravity flow would be the most practicable combination of technologies. Facilities to control the CSOs comprise of two deep underground tunnels to store CSOs and convey the stored flow to BPAWWTP; a system of diversion chambers, diversion sewers, and drop shafts to convey excess flow to the tunnels; and two overflow structures. Additionally, the plan provides for control of surface and basement flooding in the Northeast Boundary Area of the District.
DC WASA conducted environmental reviews throughout development of the ARPs and has documented its findings in this Environmental Assessment (EA). This EA evaluates the potential environmental effects of the ARPs and proposes mitigation for unavoidable impacts. DC WASA has prepared this EA in accordance with the National Environmental Policy Act (NEPA) of 1969 (42 U.S.C. 4321 and 4331-4335) and implementing regulations, 40 Code of Federal Regulations (CFR) 1500 1508. Because a considerable portion of the ARPs would cross National Park Service (NPS) property, this EA was prepared using NPS standards and addresses several NPS Director's Orders (DOs) including NPS Director's Order 12 and Handbook, Conservation Planning, Environmental Impact Analysis, and Decision-making (NPS 2001). Compliance with Section 106 of the National Historic Preservation Act of 1966 (16 U.S.C. 470) has occurred in conjunction with the NEPA process.