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Great Bay Total Nitrogen General Permit

EPA Region 1 has issued the Great Bay Total Nitrogen General Permit for 13 eligible wastewater treatment facilities (WWTFs) that discharge treated wastewater containing nitrogen within the Great Bay watershed in New Hampshire. The General Permit was issued on November 24, 2020 and will be effective beginning on February 1, 2021. Eligible facilities may submit a Notice of Intent to be covered by this General Permit until the deadline of April 1, 2021

The General Permit establishes total nitrogen effluent limitations, monitoring requirements, reporting requirements and standard conditions for 13 eligible WWTFs in New Hampshire. The discharge of all pollutants other than nitrogen from these WWTFs will continue to be authorized by each WWTF's respective individual NPDES permit.


The Great Bay estuary is composed of a complex network of tidal rivers, inland bays, and coastal harbors. The estuary receives treated wastewater effluent containing nitrogen from 17 WWTFs located in New Hampshire and Maine. Additionally, the estuary receives a significant nitrogen load from a variety of nonpoint sources and stormwater point sources throughout the watershed. Upon an evaluation of years of ambient monitoring data and other relevant technical and scientific information, EPA has determined that the nitrogen load is exceeding the assimilative capacity of the estuary and is causing or contributing, or has the reasonable potential to cause or contribute, to pervasive nutrient-related impairments and violations of water quality standards.

EPA has developed this General Permit to address a difficult environmental regulatory problem with the goal of restoring the designated uses throughout the estuary. When confronting the challenge of controlling or accounting for discharges into a complex waterbody like the Great Bay estuary, which is dominated by nonpoint source nitrogen loading, EPA considered a variety of potential permitting approaches. Rather than address this permitting task on a permit-by-permit basis, EPA instead fashioned a general permit designed to comprehensively regulate nitrogen loading from 13 WWTFs in New Hampshire on a gross, watershed-wide scale, incorporating an innovative and adaptive approach to achieving water quality standards in the Great Bay estuary through a combination of mandatory load limits at the WWTFs and voluntary nonpoint source nitrogen reductions.

One objective of the load limits established for the WWTFs is that limited investments would be necessary for facility upgrades in the short term, with potential investments only occurring in the long term if flows increase (based on growth) and the facility must then treat nitrogen to a lower concentration in order to continue to meet the load limit at higher flows. This trade-off allows municipalities to plan for immediate and ongoing voluntary investments in nonpoint source and stormwater point source nitrogen reductions, while planning for and incorporating investments at the WWTFs, if necessary, in the future.

This General Permit is structured to be opt-in, allowing the municipalities to choose whether to obtain coverage under the adaptive approach of the General Permit or to have nitrogen limits imposed by EPA through the renewal process of their individual permits. Those individual permit limits (for WWTFs that do not opt-in to be covered by the General Permit) will be calculated on a straightforward water quality basis to ensure that the discharge does not cause or contribute to a violation of water quality standards, and will not reflect the flexibilities associated with the system-wide, adaptive management approach contained in the General Permit (i.e., without forestalling WWTF upgrades in favor of voluntary nonpoint source reductions).

The Final General Permit and Response to Comments may be found at the links below. The Draft General Permit and Fact Sheet are also provided for reference.

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General Permit Documents

For reference only:

How to Obtain Coverage under this General Permit

To obtain coverage under this General Permit, WWTFs identified in Part 1.1 of the General Permit may, at their election, submit a Notice of Intent (NOI) to EPA by April 1, 2021. See Part 4 of the General Permit for more details regarding how to submit a NOI.

EPA Contacts

Michael Cobb (, 617-918-1369

Dan Arsenault (, 617-918-1562

Samir Bukhari, Esq. (Office of Regional Counsel) (, 617-918-1095

NHDES Contacts

Stergios Spanos (, 603-271-6637

Hayley Franz (, 603-271-0671