Proactive Incorporation of Sea Level Rise into the Design of the Deer Island Wastewater Treatment Plant

Created: 12/18/2010 - Updated: 3/02/2020


In the 1980s, the Massachusetts Water Resources Authority began to plan for a new wastewater treatment plant on Deer Island in Boston Harbor. The treatment plant’s effluent is discharged through a gravity fed pipe into Boston Harbor. Planners were concerned that projected sea level rise would disrupt the gravity fed pipe, requiring the installation of pumps. The planners decided to elevate the entire wastewater treatment plant by 1.9 feet to accommodate for projected sea level changes through 2050, the planned lifetime of the facility.


The Massachusetts Water Resources Authority (MWRA) serves over 2.5 million people in eastern and central Massachusetts in the greater Boston region. It was created in 1985, replacing the Metropolitan Sewer District (1889-1985). The MWRA currently has more than $6 billion invested in infrastructure and supporting facilities and manages all sewer and water plants for the greater Boston area. 

One of the MWRA’s primary wastewater treatment plants was built on Deer Island, located in Boston Harbor with over 2.6 miles of shoreline. The island houses the Deer Island Primary Wastewater Treatment Plant and over 60 acres of parkland. In 1938, erosion resulting from a hurricane connected the island to the mainland.


In 1968, the original Deer Island Primary Wastewater Treatment Plant was completed. It underwent a substantial overhaul in the 1980s to meet Federal and State pollution standards to protect Boston Harbor. The new plant cost over $3.8 billion to construct and began operating in 1995.

During the update, the MWRA opted to take into consideration the future effects sea level rise could pose to the facilities. The effluent from the sewage treatment plant is discharged through a gravity fed downhill pipe. Planners were concerned that sea level rise would require a protective wall around the plant. If this were to happen, the Deer Island facility would have to install pumps to transport the effluent over the wall. 

The plant was built 1.9 feet higher than it would otherwise have been to accommodate predicted sea level rise through 2050, the planned life of the facility. Construction on Deer Island Wastewater Treatment Plant was completed in 1998.

Outcomes and Conclusions

The Deer Island Wastewater Treatment Plant's planners proactively incorporated the potential impacts of sea level rise into their initial building codes. In this case, it was calculated to be less expensive to build the facility at a higher height in the original design rather than trying to incorporate protective barriers in the future. The plant’s 9.5 mile, 24 foot diameter outfall tunnel should remain functional through 2050 regardless of the effects of sea level rise within Boston Harbor.


Information was collected from online resources. Updated 12/18/10


Feifel, K. (2010). Proactive Incorporation of Sea Level Rise into the Design of the Deer Island Wastewater Treatment Plant [Case study on a project of the Massachusetts Water Resources Authority]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE:… (Last updated December 2010)

Project Contact(s)

MWRA is a Massachusetts public authority established by an act of the Legislature in 1984 to provide wholesale water and sewer services to 2.5 million people and more than 5,500 large industrial users in 61 metropolitan Boston communities.


Scale of Project
Community / Local
Sector Addressed
Transportation / Infrastructure
Water Resources
Target Climate Changes and Impacts
Infrastructure damage
Salinization / Saltwater intrusion
Sea level rise
Climate Type
3-5 years
Type of Adaptation Action/Strategy
Natural Resource Management / Conservation
Incorporate future conditions into natural resources planning and policies
Design protected areas or lands to allow inland, altitudinal, or latitudinal movement
Initiate targeted research program
Sociopolitical Setting
Effort Stage