MWRA's sewage treatment system has undergone a nearly complete transformation under the federally mandated 11-year, $3.8 billion Boston Harbor Project. The project, which is now complete, included a new sludge-to-fertilizer facility; the Deer Island Treatment Plant with primary and secondary treatment capabilities; the Inter-Island Tunnel that tied together two separate sewer systems (North and South) into one; and the 9.5-mile Effluent Outfall Tunnel to discharge treated wastewater away from shallow Boston Harbor waters and into the deeper waters and stronger currents of Massachusetts Bay.

DEER ISLAND WASTEWATER
TREATMENT PLANT
The centerpiece of MWRA's
Boston Harbor Project