The Cottage Farm Detention and Chlorination Station was placed in operation by the Metropolitan District Commission on April 29, 1971. The station, located in Cambridge, Massachusetts, diverts and treats combined sewage flows from the Charles River Valley sewer system (15,600 acres) which exceed the capacity of the trunk sewer to the Deer Island Treatment Plant. A maximum of 233.1 million gallons per day of excess combined sewage may be diverted to the station. The Cottage Farm Station, together with the North and South Charles Relief Sewers, collects and treats by screening, skimming, chlorination and settling all flows up to the magnitude of the five-year design storm. Flows up to 1.3 million gallons (MG) are entirely contained in the six detention tanks (1.2 MG) and wet well (0.1 MG) and are fed back to the sewer system as downstream capacity becomes available. The Cottage Farm Station has achieved significant removals of suspended solids (estimated 45% overall removal), coliform bacteria (99.9% removal), settleable solids (69%) and biochemical oxygen demand (42%) at an estimated cost of $293 per million gallons treated.