The Project generates hydropower at MWRA’s Deer Island Wastewater Treatment Facility. Once treated wastewater is disinfected, it is discharged into Effluent Channel 1. Flow is then split through two horizontal intake openings at base of Effluent Channel 1 and transmitted through separate rectangular concrete conduits below the disinfection basin to two corresponding hydro turbines. The two intake openings in Effluent Channel 1 are each approximately 20 feet by 18 feet. The intakes decrease to 11 feet by 11 feet at motorized roller intake gates located immediately upstream of the turbines. The average head available is approximately 29 feet. The hydropower facilities include two nominal 1,000 kw Kaplan units, each with flow capacity of approximately 500 cfs (320 mgd). The maximum flow (640 mgd) is approximately equivalent to the maximum flow through secondary treatment at DITP. Turbine runner blades and wicket gates are adjusted to meet changing power demands and changes in flow and head. After the turbines, the turbine effluent conduit joins the outfall chute which discharges into the outfall shaft which drops the effluent into the 9.5 mile outfall tunnel to Massachusetts Bay.

Project Name Deer Island
LIHI Certificate Number 43
LIHI Effective and
Expiration Dates
August 6, 2014
August 6, 2019
Owner Massachusetts Water Resource Authority
State Massachusetts
Location Located on the Deer Island Wastewater Treatment Plant on Deer Island in Boston Harbor, Boston, Massachusetts.
Installed Capacity 2,000 kW
Average Annual Generation 5,000,000 KWh
Facility Type
FERC No. 11412

The hydropower facilities’ instrumentation and control system is designed to interface with the DI wastewater treatment facilities control system. The system allows fully automatic unattended operation. The treatment plant must operate continuously to prevent backups of the sewage collection system. Wastewater flow in excess of the hydro facility bypasses Effluent Channel 1 and is discharged through Effluent Channel 2 directly to the outfall tunnel. The building that houses the turbines, generators and all associated electrical switchgear equipment is situated directly over Effluent Conduit 1.

The building that houses the turbines, generators and all associated electrical switchgear equipment is situated directly over Effluent Conduit 1. An aerial view of the Deer Island Treatment plant is shown above; the structure housing the hydropower installation is indicated in the lower right hand corner of the figure and is within the configuration of the treatment plant. The building is bordered to the north by the outfall tunnel shaft, on the east by a seawall and MA Bay, on the south by disinfection basins, and on the west by secondary clarifiers. A profile and cross-sectional view of the hydropower facility are included in Figures 2 and 3. The facility is located some 200 feet from the shoreline and does not impact fisheries, wildlife, flood control, or navigation.

The Project is a conduit facility and received a conduit exemption from FERC. The hydroelectric facility was also part of a thorough environmental review by state and federal agencies as part of the Deer Island Water Treatment Plant. The Deer Island Treatment Plant discharges, including all discharges through the hydropower plant, received both an EPA NPDES permit and MA Division of Water Pollution Control Water Quality Certification for all discharges through hydropower plant.

Certification History

November 19, 2014 – Executive Director Michael J. Sale, using authority delegated from the LIHI Governing Board, has determined that the Deer Island Hydroelectric Project (FERC No. 11412) continues to meet the LIHI Certification Criteria.  The effective date of the certificate is August 6, 2014, and the certificate will expire on August 6, 2019.

June 4, 2014: The Low Impact Hydropower Institute received an application for a second term of certification of the Deer Island Hydropower Project. The application materials can be found in the “Files” section below.

October 22, 2009: The Deer Island Hydroelectric Project has been certified as low impact for a five year term, effective August 6, 2009 and expiring August 6, 2014.

August 6, 2009: The Massachusetts Water Resource Authority has submitted an application for certification of the Deer Island Hydroelectric Project. A public comment period will remain open until October 6, 2009.