The plant has been constructed under a schedule established and overseen by a federal district court judge to achieve compliance with the federal Clean Water Act. Many design and engineering firms, construction contractors, subcontractors, vendors and more than 16,000 union crafts people and laborers have worked together to build the Deer Island plant. About 350 MWRA employees, including plant operators, maintenance trades-people, engineering personnel, management workers, and laboratory staff now run the plant. Each 186 foot long and 41 foot wide tank is about 40 feet deep. Sludge is pumped from the clarifiers after settling.
Scum is removed by the skimmers at the top of the tank at left.
After the mixing and reactor tanks, the final stage of secondary treatment takes place in these uncovered, stacked clarifiers. Pumps then lift the influent about 150 feet to the head of the plant. There are three main pump stations. The North System is served by the North Main Pump Station and the Winthrop Terminal Headworks, containing ten 3,500 hp pumps and six 600 hp pumps. The capacity for the North System is 910 mgd.