EPA's Permit for the Massachusetts Water Resources Authority (MWRA) Deer Island Treatment Plant Outfall and CSOs

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In fall 2000, the Massachusetts Water Resources Authority (MWRA) completed construction of a multibillion dollar sewage treatment facility on Deer Island in Boston Harbor. This facility provides secondary treatment to wastewater from 43 cities and towns in the Greater Boston area. The NPDES permit currently in effect for the facility's discharge was issued on May 20, 1999 and a modification issued on August 10, 2000 (2000 permit). This permit is now up for renewal and a revised draft permit and fact sheet has been developed to explain the new requirements and the basis for these requirements.

The 2023 draft permit imposes rigorous conditions to ensure the protection of Massachusetts and Cape Cod Bays. Each requirement is detailed in the 2023 draft permit and explained in the accompanying fact sheet.

Key permit conditions in the 2023 draft permit include:

  • Effluent Limits
    The 2023 draft permit includes numeric limits for suspended solids; bacteria; pH; chlorine; "CBOD" (oxygen-demanding material), oil and grease, and whole effluent toxicity. Some limits are new or revised from the 2000 permit based on new Massachusetts Water Quality Standards or new data.

  • Monitoring
    The 2023 draft permit requires the MWRA to monitor its discharge for a wide range of pollutants. There are monitoring requirements for all pollutants for which there is an effluent limit. In addition, the 2023 draft permit includes monitoring requirements for other pollutants in order to make permitting decisions in the next permitting cycle, such as for priority pollutants and per- and polyflouroalkyl substances (PFAS). Monitoring data submitted electronically to EPA in accordance with the reporting requirements in the permit will be publicly available via EPA's Enforcement and Compliance History Online (ECHO) website.

    In addition to requiring the MWRA to monitor the discharge itself, the 2023 draft permit continues to require that MWRA monitor the water quality in Massachusetts and Cape Cod Bays. Known as the "Ambient Monitoring Plan", these requirements have been updated to focus on new or remaining questions related to the potential impact of the discharge on Massachusetts Bay.

  • Pretreatment
    The 2023 draft permit requires that the MWRA continue to implement an industrial pretreatment program to control the discharge of pollution into the MWRA sewer system. The 2023 draft permit includes annual sampling for per- and polyflouroalkyl substances (PFAS) for selected industrial dischargers.

  • Operation and Maintenance
    The 2023 draft permit includes updated operation and maintenance requirements, consistent with state regulations, in order to ensure that sewer system infrastructure, such as sewer pipes and pump stations, and the treatment facilities are properly operated, maintained and resilient. These include contingency measures, such as maintaining alternative power systems in case of power outages, preventing groundwater and rainwater from entering the sewer system, and evaluating and implementing measures to maintain system operation in the event of major storm and flood events.

    The 2023 draft permit applies the operation and maintenance requirements to the 43 satellite communities that contribute wastewater to the MWRA Deer Island Treatment Plant. These communities are included in the permit as "co-permittees" and are only responsible for the operation and maintenance of the collection systems that they own and operate. Co-permittees are not responsible for operation of the treatment facility or for meeting Deer Island effluent limits. The 2023 draft permit includes annual reporting requirements for co-permittees.

  • Combined Sewer Overflows (CSOs)
    The permit includes conditions related to combined sewer overflows, such as a requirement that any discharges from such overflows must not contribute to the exceedance of water quality standards. The 2023 draft permit also incorporates CSO requirements for the four satellite collection systems (Boston Water and Sewer Commission, Cambridge, Chelsea and Somerville) that were previously regulated in separate permits.

2023 Draft Permit

2023 Fact Sheet

2023 Public Notice

2023 Public Comments Received

2023 Press Releases

2023 Draft Permit Public Information Sheet

1999 Final Permit (as modified in 2000)

You may contact:
Michele Cobban Barden (barden.michele@epa.gov)
Environmental Scientist
EPA Region 1
5 Post Office Square, Suite 100 (Mail Code 06-1)
Boston, MA 02109-3912
617-918-1539

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Last updated on September 18, 2024