Washington, D.C. is building underground storage capacity as its primary strategy to address CSOs. In 2011 the city began construction on a system of four deep storage tunnels, adjacent to the Anacostia River, that will reduce overflows to the river by 98 percent, and 96 percent system-wide. The system will comprise over 18 miles of tunnels with a storage capacity of 157 million gallons. The first segment of the tunnel system, 7 miles in length, went online in 2018. The remaining segments of the storage system are scheduled for completion in 2023. (The city's overall "Clean Rivers" project, projected to cost $2.6 billion, includes other components, such as reducing stormwater flows.) The South Boston CSO Storage Tunnel is a similar project, completed in 2011.