The South Boston CSO Storage Tunnel, also known as the North Dorchester Bay CSO Storage Tunnel, is a large underground facility designed to reduce untreated sewage discharges into

Boston Harbor Boston Harbor is a natural harbor and estuary of Massachusetts Bay, located adjacent to Boston, Massachusetts. It is home to the Port of Boston, a major shipping facility in the Northeastern United States. History 17th century Since its dis ...

from the

Massachusetts Water Resources Authority The Massachusetts Water Resources Authority (MWRA) is a public authority in the Commonwealth of Massachusetts that provides wholesale drinking water and sewage services to 3.1 million people in sixty-one municipalities and more than 5,500 large ...

combined sewer and stormwater system. It was opened on July 23, 2011, and is part of the federally mandated Boston Harbor Cleanup project. CSO stands for

Combined Sewer Overflow A combined sewer is a type of gravity sewer with a system of pipes, tunnels, pump stations etc. to transport sewage and urban runoff together to a sewage treatment plant or disposal site. This means that during rain events, the sewage gets dilute ...

. The main part of the facility is a tunnel in diameter, running along the harbor front. The tunnel starts at an Odor Control Building continues along the harbor front, with a midpoint near and ends with a pump station at

Combined sewer A combined sewer is a type of gravity sewer with a system of pipes, tunnels, pump stations etc. to transport sewage and surface runoff, urban runoff together to a sewage treatment plant or disposal site. This means that during rain events, the se ...

s are problematic because during heavy storms, they are forced by a high volume of rainwater from

storm drain A storm drain, storm sewer (United Kingdom, U.S. and Canada), highway drain, surface water drain/sewer (United Kingdom), or stormwater drain (Australia and New Zealand) is infrastructure designed to drain excess rain and ground water from i ...

s to carry untreated

sanitary sewer A sanitary sewer is an underground pipe or tunnel system for transporting sewage from houses and commercial buildings (but not stormwater) to a sewage treatment plant or disposal. Sanitary sewers are a type of gravity sewer and are part of ...

output into Boston harbor, including dangerous amounts of human waste. In addition to the tunnel project, the MWRA is undertaking costly sewer separation in parts of South Boston near the Reserved Channel, and reconfiguring various drains and outflows. The tunnel provides a buffer to allow some combined sewers to remain in service. It has sufficient buffer capacity to hold combined sewage and rain water during most storms, helping to eliminate the Combined Sewer Outflow events that polluted nearby beaches on average 20 times per year. After the storm is over, the tunnel is "dewatered" back into the network at a rate the

Deer Island Waste Water Treatment Plant The Deer Island Waste Water Treatment Plant (also known as Deer Island Sewage Treatment Plant) is located on Deer Island, one of the Boston Harbor Islands in Boston Harbor. The plant is operated by the Massachusetts Water Resources Authority ...

can handle.

References

External links

Massachusetts Water Resources Authority
Sewage treatment plants in Massachusetts Buildings and structures in Boston 2011 establishments in Massachusetts {{Civil-engineering-stub