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EPA Extends Comment Period on Draft Clean Water Act Permit for Great Bay

Contact Information: 
John Senn (

PORTSMOUTH, N.H. – The U.S. Environmental Protection Agency (EPA) has extended the public comment period on the draft Clean Water Act permit for New Hampshire's Great Bay by 30 days to allow for additional input from stakeholders. The new deadline for members of the public to submit comments to EPA is April 8, 2020. If finalized as proposed, EPA believes this draft permit could result in significant decreases in nitrogen discharges to New Hampshire's Great Bay estuary, improving water quality and the health of ecosystems throughout the estuary.

The 12 communities that would be covered by the general permit are: Dover, Durham, Epping, Exeter, Milton, Newfields, Newington, Newmarket, Portsmouth, Rochester, Rollinsford and Somersworth. The draft permit was issued under the Clean Water Act's National Pollutant Discharge Elimination System (NPDES). Persons or entities interested in commenting on the permit can do so by following the instructions in the Federal Register at:

Components of the Draft Permit

The draft permit includes requirements designed to ensure that Great Bay meets water quality standards established by New Hampshire. The permit also contains a monitoring program to ensure that EPA and the public are able to track the effectiveness of the permit in restoring water quality.

The permit includes:

Nitrogen requirements based on peer-reviewed science: The permit's nitrogen requirements are based on a target of 100 kilograms per hectare per year (kg/ha-yr), which is the upper end of a range of potential targets identified in a review of scientific literature, including three scientific articles that were independently peer reviewed for publication in scientific journals. The target is consistent with recent water quality improvements that have been observed in a much larger estuary in New England, Rhode Island's Narragansett Bay.

Adaptive management approach: The target of 100 kg/ha-yr is not itself a permit requirement; it is a judgment based on the best available science about how much nitrogen reduction will be needed to meet New Hampshire's water quality criteria. This initial target may change over time as part of the permit's proposed "adaptive management" approach, which relies on monitoring conditions in Great Bay as nitrogen is reduced to determine whether the target should be adjusted up or down to achieve water quality standards.

Focus on "non-point" sources: To meet the nitrogen target, the permit sets achievable reductions at the 13 wastewater treatment facilities in the 12 communities, and also assumes that Great Bay communities will make significant reductions in other sources of nitrogen—for example, stormwater runoff and "non-point" sources (such as fertilizer or septic systems). This assumption is based on the desire expressed by many Great Bay communities to invest in reductions of these other sources, possibly avoiding the need to invest in significant upgrades of wastewater treatment facilities.

Optional non-point source reductions: Non-point source reductions are optional—they are not required by the permit. Many of the Great Bay communities expressed a preference to reduce nitrogen through non-point source controls rather than wastewater treatment facility upgrades, and EPA designed the permit to allow that local choice. If the optional non-point source reductions don't occur, wastewater treatment facilities may need to further reduce nitrogen in the future to meet water quality standards.

Local flexibility: The draft permit requires municipal wastewater facilities to meet nitrogen discharge limits, which are achievable by most of the communities with their current wastewater facilities. If a municipality experiences significant growth at some point in the future, the permit allows the community the flexibility to address increasing nitrogen loads through optional non-point source reductions and, if necessary, through upgrades at its wastewater treatment facility.

Implementation and affordability: The draft permit's requirements for wastewater treatment plants can be achieved by most of the facilities through optimization of their existing treatment processes, without costly upgrades. The optional non-point source reductions are designed to be implemented in a phased manner over more than two decades; this phased approach should ensure that that the work remains affordable. The permit's adaptive management approach ensures that the schedule for this work will be revisited every five years when the permit is reissued. As with all NPDES permits, adjustments to the schedule can be made if necessary to preserve affordability. The draft permit does require participation in a program to monitor Great Bay; this monitoring is essential to the adaptive management approach, because it will help determine when Great Bay has met water quality standards and no further nitrogen reductions are necessary.

For more information on NPDES permits, go to:

For more information about EPA's work in New Hampshire, go to: