The Commission owns and operates 
a system for the collection and transport of waste- water and storm drainage in the City of Boston. The original backbone of the sewer system was the Boston Main Drainage System ("BMDS"). The BMDS was constructed from 1877 to 1884 under the direction of a special committee established by the City of Boston for that specific purpose. The original system consisted of five combined interceptors, the Calf Pasture pumping station and the Dorchester Bay Tunnel (neither the pumping station nor the tunnel is now in use).

The BMDS interceptors were initially designed to carry a peak dry weather sanitary flow together with an allowance for stormwater. 

In 1988, construction of the Boston Main Interceptor and the East Side Interceptor was completed, replacing portions of the original system. These interceptors serve the sewer needs of downtown Boston, the South End, Roxbury, Dorchester and South Boston. They increase capacity and virtually eliminate dry weather overflows. The volume of wet weather overflows has been reduced as well. The BWSC constantly monitors the city’s systems for prevention and maintenance.

 

Other collection facilities provide sewer services to different parts of the city.  Charlestown is served by a separated system, except for one small section.  East Boston, South Boston, Roxbury and the City Proper are served mainly by combined systems.  The South End has been partially separated under a program initiated by the City’s urban renewal program, and continued by the Commission where feasible and cost effective.  Allston/Brighton, Roslindale, West Roxbury, Hyde Park, Mattapan and portions of Dorchester and Jamaica Plain, all of which are located in the southern part of the City, are essentially served by separate systems installed between 30 and 80 years ago.  Large areas of Jamaica Plain and Dorchester are currently being separated under a Combined Sewer Overflow reduction program.