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EPA's Permit for the Massachusetts Water Resources Authority (MWRA) Outfall

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In fall 2000, the Massachusetts Water Resources Authority (MWRA) Exit completed 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 for the facility's discharge was issued on May 20, 1999 and modified on July 10, 2000.

On January 13, 2003 the federal Environmental Protection Agency (EPA) proposed a second modification to the permit that (i) adds reporting requirements to the sludge monitoring requirement and (ii) revises numerical limitations and monitoring requirements for the MWRA's combined sewer overflows, based on the most current MA water quality standards. All other conditions of the existing permit, including effluent limitations and monitoring requirements, will remain unchanged. The public notice period for the proposed modification is closed. Response to comments and the final issuance permit modification will be posted here, when available. Read the draft permit modification.

The current permit imposes rigorous conditions to ensure the protection of Massachusetts and Cape Cod Bays. In fact, the permit is the most comprehensive of its type ever issued for a municipal discharger. The permit includes unprecedented ambient monitoring requirements; stringent pollution prevention, and best management practice requirements; and a first-of-its-kind requirement to implement a "contingency plan," Exit to help ensure that any unexpected problems are dealt with swiftly.

Key permit conditions include:

  • Effluent Limits
    The permit includes numeric limits for suspended solids; fecal coliform bacteria; pH; chlorine; PCBs; and "CBOD" (oxygen-demanding material). In addition, state water quality standards establish limits for 158 pollutants, and the permit prohibits any discharge which would cause or contribute to an exceedance of any of those limits. A requirement has been added to the permit to prohibit the discharge of nutrients in amounts which cause eutrophication.

    Because some chemicals may have synergistic effects, the permit also requires the MWRA to periodically test the toxicity of the effluent as a whole on sensitive marine organisms, and establishes strict limits based on those tests.

  • Monitoring
    The permit requires the MWRA to monitor its discharge for a wide range of pollutants. Monitoring results will be reported to EPA and DEP each month, and all monitoring data will be available to the public.

    In addition to requiring the MWRA to monitor the discharge itself, the permit also requires the MWRA to implement the most extensive ambient monitoring program (i.e. monitoring of conditions in Massachusetts and Cape Cod Bays) for any treatment plant of its kind in the United States. This multimillion dollar program includes 43 monitoring stations which will collect data on everything from nutrients to heavy metals to algae blooms. Monitoring results will be compared with an extensive set of pre-discharge baseline data, to help assess any impact of the discharge.

    To increase the availability of monitoring data to the public, provisions have been added to the permit requiring distribution of key data via the internet.

    To assist EPA and DEP in evaluating monitoring results and developing appropriate revisions to the monitoring plan, and to ensure that the best possible science is brought to bear on issues of environmental health, EPA and DEP have created an Outfall Monitoring Science Advisory Panel. This panel consists of independent researchers in key fields, who meet to analyze monitoring data, interpret the results, and provide expert opinion on issues concerning the impact of the outfall. The science panel's meetings are open to the public.

  • Contingency Plan
    The permit requires the MWRA to implement a contingency plan, which establishes "caution" and "warning" levels for a range of environmental indicators (for example, frequency of red tide blooms, or levels of toxics in fish tissue). If a warning level is exceeded, the MWRA must determine whether any adverse environmental impacts are occurring. If they are, the MWRA must develop a plan to prevent such impacts. A report on these efforts must be submitted to EPA and DEP (and made available to the public) every thirty days until the issue has been resolved. The permit places the burden of proof on the MWRA to show that it is not contributing to any environmental problems.

    The permit also requires that the MWRA maintain and update a comprehensive survey of nitrogen removal technologies, to minimize the time needed to implement nitrogen removal if that becomes necessary. The permit also requires that the MWRA maintain reserve funds to address unexpected contingencies.

  • Pollution Prevention
    EPA and DEP strongly encourage efforts to prevent pollution at the source. The permit requires that the MWRA develop and implement a pollution prevention plan that encompasses all users of the MWRA system--industrial, commercial, and residential. There is a special focus on efforts to reduce PCBs, including monitoring of industries where PCBs are typically found, requiring implementation of spill containment measures, and taking enforcement action when PCBs are discharged.

  • Other conditions
    The permit limits average dry weather flow and restricts the MWRA's service area to include only the 43 cities and towns currently part of the MWRA wastewater system.

    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 permit requires that the MWRA implement an industrial pretreatment program to control the discharge of pollution into the MWRA sewer system.

    The permit includes requirements designed to reduce infiltration and inflow into the sewer system.

    The permit requires that the MWRA implement a best management practices plan to minimize contamination in runoff from the Deer Island treatment plant; from headwork stations; from CSO treatment facilities; and from its sludge pelletizing facility at Fore River.

    The permit requires monthly monitoring of the sludge (the solids which settle out during the treatment process) produced by the Deer Island treatment plant, and contains conditions for the use and disposal of that sludge.

    The permit includes a reopener clause which allows EPA and DEP to add additional limits or requirements if new information becomes available.

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The Permit

You may contact:
Janet Deshais ( or  (617) 918-1667), EPA - if you have any questions.

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