Clean Water Act discharge permit · NPDES NH0100161
MERRIMACK WASTE WATER TREATMENT PLANT, Merrimack, NH: NPDES NH0100161 discharge permit, effluent exceedances, inspections, penalties
- Administratively continuedPermit status
- MajorDischarger class
- 20Pollutants under a numeric limit
- 7Pollutants with an effluent exceedance
MERRIMACK WASTE WATER TREATMENT PLANT, held by MERRIMACK W W T F, holds NPDES permit NH0100161, which discharges to Merrimack River. EPA’s file records it issued September 25, 2007 and expiring November 30, 2012. The status and dates are as EPA’s permit file stood when Velarion loaded it (September 15, 2026); EPA’s free Detailed Facility Report on ECHO carries the permit’s current standing.
Identity
| Facility as filed | MERRIMACK WASTE WATER TREATMENT PLANT |
|---|---|
| Permittee as filed | MERRIMACK W W T F |
| NPDES ID | NH0100161 |
| Permit status | Administratively continued (past its expiration date and still in force until reissued) |
| Permit type | Individual permit |
| Discharger class | Major discharger |
| Facility type | Publicly owned treatment works |
| Program | Publicly owned treatment works |
| Issued | September 25, 2007 |
| Expiration date | November 30, 2012 |
| Address | Merrimack, NH 03054 |
| Receiving water | MERRIMACK RIVER |
| Receiving water impaired | 303(D) Listed |
| Subwatershed | Nesenkeag Brook-Merrimack River (HUC 010700061002) |
Cited to the EPA ICIS-NPDES permit file (ECHO download).
Effluent limits and exceedances
- 22Pollutants on file
- 20Under a numeric limit
- 9With a violation of any kind
- 7With an effluent exceedance
An effluent exceedance is a discharge monitoring report value over the permit’s numeric limit (EPA’s violation code E90). A violation of any kind also counts a report not filed. Each row is EPA’s own count for that pollutant.
| Pollutant or measure | Limits | Violations, any kind | Effluent exceedances | Latest exceedance | Largest exceedance, as filed |
|---|---|---|---|---|---|
| E. coli, thermotol, MF, MTEC | 2 | 41 | 41 | February 28, 2014 | 99,999% over the limit |
| E. coli, colony forming units [CFU] | 0 | 23 | 21 | April 30, 2025 | 496% over the limit |
| Chlorine, total residual | 2 | 9 | 9 | November 30, 2023 | 99% over the limit |
| Solids, total suspended | 9 | 7 | 4 | March 31, 2010 | 154% over the limit |
| pH | 2 | 3 | 3 | July 31, 2026 | |
| BOD, 5-day, 20 deg. C | 9 | 2 | 2 | March 31, 2010 | 106% over the limit |
| LC50 Static 48Hr Acute Ceriodaphnia dubia | 1 | 1 | 1 | September 30, 2009 | 36% over the limit |
| Solids, suspended percent removal | 1 | 1 | 0 | ||
| Phosphorus, total [as P] | 0 | 1 | 0 | ||
| Flow, in conduit or thru treatment plant | 3 | 0 | 0 | ||
| Flow, process wastewater | 3 | 0 | 0 | ||
| Nitrogen, ammonia total [as N] | 1 | 0 | 0 | ||
| Hardness, total [as CaCO3] | 1 | 0 | 0 | ||
| Nickel, total recoverable | 1 | 0 | 0 | ||
| Zinc, total recoverable | 1 | 0 | 0 | ||
| Aluminum, total recoverable | 1 | 0 | 0 | ||
| Cadmium, total recoverable | 1 | 0 | 0 | ||
| Lead, total recoverable | 1 | 0 | 0 | ||
| Chromium, total recoverable | 1 | 0 | 0 | ||
| Copper, total recoverable | 1 | 0 | 0 | ||
| BOD, 5-day, percent removal | 1 | 0 | 0 | ||
| LC50 Static 48Hr Acute Pimephales promelas | 1 | 0 | 0 |
Cited to the EPA ICIS-NPDES limits and effluent violations files (ECHO download); up to 60 rows shown, most exceedances first.
Inspections, violations and enforcement
- 11Single-event violations
| Date | What EPA recorded | Agency |
|---|---|---|
| June 30, 2026 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| June 26, 2026 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| April 28, 2025 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| April 30, 2024 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| April 16, 2024 | Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment | EP6 |
| March 8, 2024 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| January 29, 2024 | Dry-weather SSO discharge to waters of the U.S. that may endanger health or the environment | EP6 |
| January 22, 2024 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| May 2, 2023 | Dry-weather SSO, no discharge to waters of the U.S., not permit compliant, no endangerment | EP6 |
| March 16, 2023 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
| August 16, 2022 | Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment | EP6 |
Velarion’s copy of EPA’s ICIS-NPDES files does not include the inspections, formal enforcement actions and informal enforcement actions files, so this page shows none of them. EPA’s free Detailed Facility Report on ECHO lists this permit’s inspections, enforcement actions and penalties.
Cited to the EPA ICIS-NPDES violation, inspection and enforcement files (ECHO download); up to 50 rows of each shown, newest first.
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EPA publishes a free Detailed Facility Report for every permit on ECHO: its compliance status quarter by quarter, its inspections, and its enforcement actions and penalties. EPA also sends free notices of new inspections and enforcement actions through ECHO Notify; enter NPDES ID NH0100161 there.
Nearby on the register
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- Every permit record in New Hampshire, A to Z
Figures from EPA’s ICIS-NPDES download, loaded September 15, 2026.