Watershed-Based Permitting Case Study
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Great Bay Watershed, New Hampshire
Great Bay Total Nitrogen General Permit
Overview
The Great Bay watershed, located in the states
of Maine and New Hampshire, is composed of
an inland estuary with a network of tidal, rivers,
inland bays, and coastal harbors. Great Bay
estuary has been listed as an estuary of
national significance under EPA's National
Estuary Program (NEP) and is a critical
resource in New Hampshire. In past years,
Great Bay has experienced significant water
quality issues related to high loads of total
nitrogen in the watershed, including low
dissolved oxygen, algae blooms, and declining
eelgrass habitats and oyster communities.
Since the 1990s, eelgrass communities in
Great Bay have declined by 50 percent, while
oyster and clam communities have declined
by over 90 percent. Sources of nitrogen to the
watershed include discharges from wastewater
treatment facilities (WWTFs) and significant
loads from various nonpoint sources and
stormwater point sources.
In November 2020, EPA issued a watershed-
based general permit for discharges of
nitrogen from WWTFs with the goal of
restoring water quality to support designated
uses in Great Bay. The discharge of pollutants
other than nitrogen from the WWTFs is
authorized by their individual NPDES permits.
EPA determined that a watershed approach
would be more expeditious and effective than
individual permit issuances. This approach
allows EPA to address total nitrogen impacts
Watershed
Great Bay, New Hampshire
Key Water Quality Concerns
Total Nitrogen
Stakeholder Involvement Techniques
Early engagement with various regulators and
stakeholders to determine the regulatory pathway most
likely to expedite restoration
Meetings with coalitions of potential municipal
permittees and other stakeholders
Stakeholder meetings to describe the scientific basis for
the permit
Public hearing at a local venue
Public comment period for draft permit review
Case Study Issues of Interest
Type of Point Sources
T~)
Publicly Owned Treatment Works Discharges
Type of Watershed-Based Permit or Approach
si Multisource Watershed-Based Permit
Highlighted Approach(es)
# Implementation of Total Maximum Daily Loads
(TMDLs) or Other Watershed Pollutant Reduction
Goals
jpn Coordinated Watershed Monitoring
*>EPA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
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and evaluate receiving water responses on a systemwide, holistic ievei. The goal of the watershed
approach is to achieve a gross reduction in total nitrogen from multiple sources at roughly the same
time.
This case study focuses on EPA's General National Pollutant Discharge Elimination System (NPDES)
Watershed Permit for Total Nitrogen Discharges in Great Bay for Wastewater Treatment Facilities in
New Hampshire (General PermitNHG58A000) and the adaptive management approach
implemented in the permit.
Background
The Piscataqua Region Estuaries Partnership collects, compiles, and analyzes monitoring data from the
Great Bay estuary to produce State of Our Estuary reports every five years. These reports include the
status of the estuary's environmental conditions, environmental trends, and overall environmental
health indicators. The environmental indicators relating to excessive levels of nutrients in the Great
Bay estuary include dissolved oxygen, total nitrogen, and eelgrass.
To confront the challenge of
controlling or accounting for
discharges into the Great Bay
watershed, which is dominated by
nonpoint source nitrogen loading, EPA
chose to implement a watershed-based
permitting approach including adaptive
management to increase monitoring
and data collection throughout the watershed. EPA translated narrative water quality criteria to
establish numeric water quality-based effluent limitations in the permit. EPA evaluated the scientific
literature and identified a range of possible nitrogen thresholds. EPA chose the least stringent
threshold within the "critical range" as a reasonable next step in an adaptive management approach.
The Agency may establish a lower threshold in the future if the system does not fully recover once the
initial threshold is achieved. This adaptive management process reduces uncertainty, builds
knowledge, and improves management over time in a goal-oriented and structured process. One
objective of EPA's adaptive management permitting approach is to give the municipalities flexibility in
achieving the most cost-effective nitrogen reductions that will maximize the benefit to water quality
throughout Great Bay as expeditiously as possible.
Permit Strategy
The watershed-based permit establishes total nitrogen effluent limitations, monitoring requirements,
reporting requirements, and standard conditions for 13 eligible WWTFs in New Hampshire's portion
of the Great Bay watershed. The discharge of pollutants other than nitrogen from these facilities
continues to be authorized by their individual NPDES permits.
Coverage under this permit is optional, allowing the municipalities to choose between controlling
nitrogen discharges through the adaptive approach of the general permit or through nitrogen limits
in their individual permits. Individual permit limits for total nitrogen are expected to result in
upgrades at the POTWs to the limit of technology {i.e., limits of 3.0 mg/L). The individual permit limit
option would not include the flexibilities associated with the systemwide adaptive management
approach in the general permit. The general permit establishes effluent load limitations for total
nitrogen for 11 of 13 eligible POTWs. One objective of the load limits established for the POTWs is
The Great Bay Total Nitrogen General Permit defines total
nitrogen as the sum of the concentrations of total Kjeldahl
nitrogen and nitrate plus nitrite nitrogen expressed as
milligrams of nitrogen per liter. The permit includes
seasonal load limits for total nitrogen (in units of average
pounds per day). Compliance with the effluent limits is
determined using rolling seasonal average loads.
oEPA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
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that limited investments would be necessary for facility upgrades in the short-term, with potential
investments only occurring if flows increase (based on growth) and the facility must treat nitrogen to
a lower concentration to meet the load limit at higher flows. This tradeoff allows municipalities to plan
for immediate and ongoing investments in nonpoint source and stormwater point source nitrogen
reductions, while planning for and incorporating investments at the POTWs, if necessary, in the future.
Although not required by the permit, EPA anticipates that communities will invest in nonpoint source
controls to achieve the nitrogen reductions necessary to meet water quality standards.
Permit Highlights
Adaptive Management Framework Voluntary Submittal
Part 3 of the watershed-based permit gives permittees the opportunity to participate in adaptive
management in collaboration with EPA; the New Hampshire Department of Environmental Services
(NHDES); and public, private, and commercial stakeholders. Elements of the adaptive management
framework include ambient monitoring, pollution tracking, source reduction planning, and review of
permit issues. If permittees elect to participate in the collaboration, they must submit a detailed
proposal to EPA within 180 days following the permit effective date including the following
information:
The approach the permittee will use to monitor the ambient water quality in the Great Bay estuary
to determine progress and trends.
The method(s) the permittee will use to track reductions and additions of total nitrogen over the
permit term.
An outline/plan for overall source reductions of total nitrogen over the permit term.
A process for evaluating any significant scientific or procedural issues relating to the permit (e.g.,
appropriate thresholds), including detailed milestones, culminating in submission of a report to
EPA for inclusion in the administrative record for the permit renewal.
A proposed timeline for completing a total maximum daily load (TMDL) for total nitrogen in Great
Bay and for submitting it to EPA for approval.
Permittees have the option of submitting their proposals individually or jointly with other permittees.
Ten of the 12 municipalities (representing 11 WWTFs) have submitted voluntary adaptive
management plans and are currently implementing the plans in collaboration with EPA and NHDES.
Permit Components
Coverage under the general permit is
only available to the 13 WWTFs located
in New Hampshire that discharge to
Class B waters in the Great Bay
watershed. These facilities have the
option of applying for coverage under
the general permit or complying with
facility-specific nitrogen limits in their individual NPDES permits. Facilities maintain coverage under
their individual permits for all other parameters. To obtain coverage under the general permit,
facilities must complete a notice of intent and submit it to EPA within 60 days following the permit
effective date. Upon receiving approval from EPA, a facility is subject to the conditions of the general
permit.
New Hampshire's surface waters are divided into two
classes. Class A waters are of the highest quality, and Class
B waters are of the second highest quality. Each class must
attain and maintain specified water quality standards (see
New Hampshire Revised Statute Annotated 485-A:8, I, II
and III).
oEPA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
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Effluent Limitations
The permit establishes seasonal load
limits for total nitrogen from April 1
through October 31 for 11 WWTFs. The
two remaining WWTFs are subject to
seasonal monitoring and reporting
requirements for the first 24 months of
the permit term. After the 24-month
period, effluent limits equivalent to the
average monthly load (in pounds per
day) from the initial 14 growing season
months (i.e., all months between April 1
and October 31) will become effective
for these facilities.
Effluent Limitations
New Hampshire's water quality standards lack numeric
nutrient criteria for Class B waters, but include numeric
dissolved oxygen criteria and narrative criteria for nutrients
and biological and aquatic community integrity. In the
absence of numeric criteria, EPA translated the relevant
narrative criteria into a numeric threshold based on several
scientific studies that evaluated nitrogen loading rates
necessary to protect estuarine environments. Effluent limits
were established for the WWTFs consistent with the
numeric threshold. Due to uncertainties in the selection of
the threshold, EPA may establish a more stringent
threshold in the future if the system does not fully recover
once the threshold is achieved. See the permit fact sheet
(pp. 21 -24) for the rationale for EPA's approach for
translating the narrative criterion.
Wastewater Treatment Facility
Rolling Seasonal Average
Total Nitrogen Effluent Limitation (lbs/day)*
Rochester
198
Portsmouth
248
Dover
167
Exeter
106
Durham
59
Somersworth
92
Pease ITP
93
Newmarket
30
Epping
43
Newington
15
Rollinsford
Report
Newfields
16
Milton
Repoi^^
The reported rolling seasonal average value must be calculated as the arithmetic mean of the monthly average
load (in lbs/day) for the reporting month and the monthly average loads (in lbs/day) of the previous six months
from April 1 through October 31 of each year (i.e., rolling seven-month average).
Permittees may request an increase of their permitted load after successfully completing septic
system or private sewer system tie-in projects, as described in Part 2.2 of the permit. Rolling seasonal
average load limits established in the permit were calculated based on the design flow of the facilities
from 2012 through 2016.
Monitoring and Reporting Requirements
General permit holders are required to conduct weekly discharge monitoring to determine
compliance with rolling seasonal average total nitrogen effluent limitations. Permit holders must
calculate and report monthly average monitoring results for total nitrogen, total Kjeldahl nitrogen,
and nitrate plus nitrite nitrogen no later than the 15th day of the month following the completed
reporting period.
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Permit Effectiveness
Environmental Benefits
The watershed-based permit has resulted in a significant focus on implementing best management
practices in the largest urban communities around the estuary. In the first year alone, the communities
funded over $20 million in projects to improve stormwater quality and optimize wastewater
treatment. The permit directly incentivized the Dover City Council to authorize the creation of a
stormwater utilitythe first in New Hampshire.
Because the permit was only recently issued, environmental benefits have not yet been quantified.
However, the watershed-based and adaptive management approaches in the permit will allow for the
Great Bay watershed to be evaluated systemwide. EPA believes this approach will result in gross
reduction of total nitrogen from multiple sources in the watershed at roughly the same time,
improving water quality and restoring designated uses for the watershed. Restoration of eelgrass
communities will also have a significant effect on the watershed by improving habitats for local
wildlife.
Benefits to the Permittee
The permit was developed to provide the permittees with several different tools for achieving
compliance. EPA established seasonal load limits for the WWTFs so that limited investments would be
necessary for short-term facility upgrades, in contrast with higher investments needed to comply with
more stringent nitrogen limits that would be required in the facilities' individual permits without the
flexibilities of the systemwide, adaptive management approach. Under the general permit, potential
investments would only occur in the long term if flows increase significantly, requiring the facility to
treat nitrogen to a lower concentration to continue to meet their seasonal load limit at higher flows.
This allows municipalities to plan for alternative, voluntary source reduction investments (which may
include nonpoint source and stormwater point source nitrogen reductions) while planning any
necessary future investments at the WWTFs. This provides facilities with a more flexible approach than
solely employing treatment upgrades at the WWTF.
Benefits to the Permitting Authority
The watershed-based permit is a more streamlined and efficient permitting approach for EPA to
reduce total nitrogen loads in Great Bay. Following years of delays and litigation from traditional
individual permitting approaches, the watershed-based permit has resulted in stakeholders working
together to achieve the necessary nutrient reductions.
Lessons Learned
Michael Cobb, the EPA Region 10 permit writer, and Ted Diers, the administrator of NHDES's
Watershed Management Bureau, shared their "lessons learned" during development of the watershed-
based permit. They identified balancing the needs of diverse stakeholders and building trust among
stakeholders as the most challenging parts of developing the watershed-based permit.
According to Mr. Cobb, facilitating discussions among stakeholders in advance helped EPA and
stakeholders work through their differences. EPA included the author of a scientific paper used to
support the nutrient target in several early meetings with permittees and environmental groups to
describe the science underlying the nutrient target. These meetings allowed stakeholders to ask
questions and gain a better understanding of the scientific basis of the permit. Additionally, EPA
conducted a public hearing at a local venue during the public comment period. The hearing was well
oEPA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
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attended and provided an opportunity for a variety of stakeholders to submit comments and listen to
comments from other stakeholders.
For Mr. Diers, overcoming mistrust among the various parties was a significant hurdle after more than
a decade of disagreement and legal challenges over nutrient management in the watershed. Working
though mistrust to get to a resolution took some give and take from all parties. The three main
strategies that built trust were 1) being open to flexible approaches, 2) creating a mediation
environment that encouraged open communication, and 3) working toward a positive solution that
everyone could believe in. When asked what could have been differently to resolve this challenge, Mr.
Diers suggested that having more open dialogue earlier in the process and entering the safety of the
mediation environment (or nondisclosure types of agreements) at an earlier stage could have helped.
Both Mr. Cobb and Mr. Diers believe this watershed-based permitting approach could be used to
achieve environmental goals in other watersheds that receive significant stormwater and nonpoint
source nutrient loads and where reductions from publicly owned treatment works alone will not
achieve water quality standards. Mr. Diers also suggested that candidate watersheds would lack a
TMDL and trading opportunities and would have multiple parties involved, elements that are difficult
to deal with in traditional NPDES regulations and permitting approaches. If the approach were to be
applied in another watershed, he recommends that the permitting authority:
Create an inclusive environment with opportunities to speak freely.
Establish opportunities for nontraditional approaches.
Build in alternative pollution reduction strategies.
Recognize that changes will take time and incremental progress is acceptable.
Create opportunities for stakeholders to share science and help form the monitoring and research
questions.
EPA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
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Resources
City of Dover. No date. Nitrogen and the Great Bay. https://www.dover.nh.gov/government/city-
operations/community-services/wastewater/nitroaen/.
U.S. Environmental Protection Agency (EPA). January 2020. EPA Draft Permit Will Significantly Reduce
Nitrogen Discharges, Improve Health of Great Bay. https://www.epa.gov/newsreleases/epa-draft-
permit-will-significantly-reduce-nitrogen-discharges-improve-health-great-bav.
EPA. No date. Draft Fact Sheet: National Pollutant Discharge Elimination System (NPDES) Great Bay
Total Nitrogen General Permit for Wastewater Treatment Facilities in New Hampshire.
https://www3.epa.gov/region1/npdes/gbtn/gbtn-draft-gp-fs.pdf.
EPA. National Poiiutant Discharge Elimination System (NPDES) Great Bay Totai Nitrogen General
Permit for Wastewater Treatment Facilities in New Hampshire. Effective February 1, 2021.
https://www3.epa.gov/region1/npdes/gbtn/nhg58a000-gbtn-gp.pdf.
EPA. No date. Response to Comments: Issuance of NPDES Permit No. NHG58A000 Great Bay Total
Nitrogen General Permit for Wastewater Treatment Facilities in New Hampshire.
https://www3.epa.gov/region1/npdes/gbtn/nhg58a000-gbtn-gp-rtc.pdf.
Great Bay Municipal Coalition. No date. Great Bay Municipal Coalition Adaptive Management Plan.
https://www.dover.nh.gov/Assets/government/city-operations/community-
services/image/b4AMP%20Summary.pdf.
New Hampshire Revised Statutes Annotated (RSA). No date. RSA Section 485-A.8 Classification of
Waters. http://www.gencourt.state.nh.us/rsa/html/l/485-a/485-a-8.htm.
Roseen, Robert M. May 2020. Feasibility Analysis for EPA's Draft Great Bay Total Nitrogen General
Permit in Dover, Durham, Epping, Exeter, Milton, New fields, Newington, Portsmouth, Rochester,
Rollinsford, Somersworth NH and Berwick, Kittery, North Berwick and South Berwick ME.
https://scholars.unh.edu/prep/444/.
Permitting Authority Contact:
Michael Cobb
U.S. Environmental Protection Agency (EPA) Region 1,
Environmental Engineer
617-918-1369
cobb.michael@epa.gov
Stergios Spanos
New Hampshire Department of Environmental Services (NHDES),
Permits and Compliance Program Supervisor
603-271-6637
stergios.spanos@des.nh.gov
Permit Information:
Permit:
https://vwwv3.epa.gov/region1/npdes/gbtn
/nhg58a000-gbtn-gp.pdf
Draft fact sheet:
https://vvvwv3.epa.gov/region1/npdes/gbtn
Znhg58a000-gbtn-gp-draft-permit-fs.pdf
Pollutants of Concern In Watershed:
Excessive nitrogen, low dissolved oxygen
(DO), and chlorophyll-a
Pollutants Addressed In Permit:
Total nitrogen
Permit Issued:
November 24, 2020
EDA Watershed-Based Permitting Case Study Great Bay Watershed, New Hampshire
tnF\ EPA-833-F-22-007 March 2023
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