Who issues NPDES permits in New Hampshire?

US EPA Region 1 (with NHDES) issues and enforces NPDES permits for wastewater discharges in New Hampshire. Klarifi tracks 46 permits held by publicly owned treatment plants in the state.

How many NPDES permits in New Hampshire are expired or administratively continued?

11 permits are administratively continued (the plant applied for renewal and the old permit stays in force) and 6 are recorded as expired, out of 46 permits tracked. 29 are effective.

How many New Hampshire wastewater permits come up for renewal soon?

28 in 2026, 4 in 2027 and 2 in 2028. Each year has its own renewal calendar with the plants listed.

How do I look up an NPDES permit number?

Enter the permit number (two letters and seven characters, for example TX0021873) or the plant name in the lookup on the NPDES page; each result opens the plant profile with status, expiry, design flow and the three-year violation count.

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NPDES permits in New Hampshire

Name: NPDES permits held by wastewater treatment plants in New Hampshire
Creator: Klarifi
License: https://klarifi.io/terms-of-service

46 permits held by publicly owned wastewater treatment plants · issued by EPA Region 1

Effective

Administratively continued

Expired

Total tracked

New Hampshire is not a delegated state: NPDES permits are issued by US EPA Region 1 (with NHDES), with the state agency handling water-quality certification. Klarifi tracks 46 permits held by publicly owned treatment plants in the state, with status, expiry, design flow and three-year compliance for each. Agency website →

An NPDES permit runs for five years. To keep discharging, a plant must apply for renewal at least 180 days before the expiry date, and the renewed permit usually arrives with tighter effluent limits, new monitoring requirements or a compliance schedule. That is why the year a permit expires is the year a plant starts budgeting for upgrades: nutrient removal, disinfection, capacity or controls.

Permit renewals by year

2026: 28 permits →

2027: 4 permits

2028: 2 permits

2029: 2 permits

Largest permit holders in New Hampshire

The 25 largest publicly owned wastewater treatment plants in New Hampshire by permitted design flow, with NPDES permit number, status and expiry. Source: EPA ICIS-NPDES via Klarifi.
Facility	City	Avg flow (MGD)	Design (MGD)	NPDES permit	Status	Expires	Violations (3y)
Nashua WWTP	Nashua	9.2	16	NH0100170	Administratively continued	May 2020	87
Wrbp Franklin Wastewater Treatment Plant	Franklin	3.53	11.5	NH0100960	Effective	Jun 2029	22
Concord Wastewater Treatment Facility	Concord	3.2	10.1	NH0100901	Effective	Aug 2027	9
Keene Wastewater Treatment Facility	Keene	1.26	6	NH0100790	Effective	Nov 2026	8
Rochester Wastewater Treatment Facility	Rochester	2.35	5	NH0100668	Effective	Jun 2028	3
Pierce Island Wastewater Treatment Plant	Portsmouth	2.38	4.8	NH0100234	Effective	Nov 2028	47
Huckleberry Hill Wastewater Treatment Facility	Dover	1.91	4.7	NHG58A003	Expired	Jan 2026	30
Leavitt E. Magrath Wastewater Treatment Facility	Hampton	2.08	4.7	NH0100625	Expired	Feb 2026	27
Derry, Town Of, Wastewater Treatment Plant	Derry	1.17	4	NH0100056	Administratively continued	Feb 2016	17
Claremont Wastewater Treatment Facility	Claremont	1.2	3.9	NH0101257	Administratively continued	Sep 2021	0
Durham Wastewater Treatment Facility	Durham	0.83	2.5	NHG58A005	Expired	Jan 2026	8
Penacook Wastewater Treatment Plant	Concord	0.18	2.37	NH0100331	Administratively continued	Jul 2025	5
Hanover Wastewater Treatment Facility	Hanover	0.99	2.3	NH0100099	Administratively continued	Jan 2021	45
Hooksett Wastewater Treatment Facility	Hooksett	0.68	2.2	NH0100129	Administratively continued	Sep 2018	1
Milford Wastewater Treatment Facility	Milford	0.78	2.15	NH0100471	Administratively continued	Oct 2025	191
Littleton Wastewater Treatment Plant	Littleton	0.27	1.5	NH0100153	Expired	Oct 2025	17
Suncook Wastewater Treatment Facility	Allenstown	0.45	1.5	NH0101390	Effective	Jan 2027	9
Merrimack WWTF	Merrimack	1.37	—	NHR053094	Administratively continued	Feb 2026	9
Lancaster Wastewater Treatment Facility	Lancaster	0.23	1.2	NH0100145	Administratively continued	Sep 2025	37
Berlin Pollution Control Facility	Berlin	1.12	—	NH0100013	Effective	Jun 2029	5
Charlestown Wastewater Treatment Plant	Charlestown	0.03	1.12	NH0100765	Administratively continued	Sep 2025	21
Exeter Wastewater Treatment Facility	Exeter	1.1	—	NHG58A004	Expired	Jan 2026	18
Lebanon Wastewater Treatment Facility	Lebanon	0.89	—	NHR053176	Administratively continued	Feb 2026	2
Waterville Valley Wastewater Treatment Plant	Waterville Valley	0.14	0.55	NH0100781	Effective	Mar 2027	6
Newmarket, Town Of - WPCF	Newmarket	0.35	—	NHG580013	Effective	Nov 2026	17

All 46 plants in New Hampshire →

NPDES permits in New Hampshire: questions

Sources and methodology

Flow, permit and violation figures come from the EPA's ICIS-NPDES discharge monitoring records. Population served comes from the Clean Watersheds Needs Survey 2022. Treatment structures are identified by Klarifi's review of aerial imagery, and capital improvement projects are extracted from published municipal budget documents. Violations are counted over the last three years of monitoring reports.

Data refreshed September 11, 2026.

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