Monitoring Results of the Massachusetts Water Resources Authority (MWRA) Outfall Relocation in Massachusetts Bay

Thirty years ago Boston Harbor was called the “dirtiest harbor in America.” The creation of the Massachusetts Water Resources Authority (MWRA) in 1984 and the construction of the 55 m3/s (1270 mgd) Deer Island wastewater treatment plant and its 15 km (9.5 mile) ocean outfall, have reversed the effects of pollution in the harbor. An outfall monitoring program was incorporated as part of the NPDES permit for the plant. Over nine years of Massachusetts Bay baseline monitoring and 15 years of of “post-outfall” monitoring have been completed, including effluent water quality, water column, sea floor, and fish and shellfish studies. Solids and metals loads have declined 90% since 1990. Nutrients have declined in Boston Harbor, and flounder health has improved dramatically. Over twenty years of coastal monitoring has shown no adverse effects attributable to the Massachusetts Bay discharge. Meanwhile, the beaches and ecosystem of Boston Harbor have rebounded.