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Clean Water Act discharge permit · NPDES NH0100161

MERRIMACK WASTE WATER TREATMENT PLANT, Merrimack, NH: NPDES NH0100161 discharge permit, effluent exceedances, inspections, penalties

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 filedMERRIMACK WASTE WATER TREATMENT PLANT
Permittee as filedMERRIMACK W W T F
NPDES IDNH0100161
Permit statusAdministratively continued (past its expiration date and still in force until reissued)
Permit typeIndividual permit
Discharger classMajor discharger
Facility typePublicly owned treatment works
ProgramPublicly owned treatment works
IssuedSeptember 25, 2007
Expiration dateNovember 30, 2012
AddressMerrimack, NH 03054
Receiving waterMERRIMACK RIVER
Receiving water impaired303(D) Listed
SubwatershedNesenkeag Brook-Merrimack River (HUC 010700061002)
Other EPA IDs (FRS)RCRA handler NHD986483386; ICIS-AIR source NH0000003301100094

Cited to the EPA ICIS-NPDES permit file (ECHO download); cross-program IDs from EPA’s FRS facility-registry crosswalk.

Effluent limits and exceedances

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 measureLimitsViolations, any kindEffluent exceedancesLatest exceedanceLargest exceedance, as filed
E. coli, thermotol, MF, MTEC24141February 28, 201499,999% over the limit
E. coli, colony forming units [CFU]02321April 30, 2025496% over the limit
Chlorine, total residual299November 30, 202399% over the limit
Solids, total suspended974March 31, 2010154% over the limit
pH233July 31, 2026
BOD, 5-day, 20 deg. C922March 31, 2010106% over the limit
LC50 Static 48Hr Acute Ceriodaphnia dubia111September 30, 200936% over the limit
Solids, suspended percent removal110
Phosphorus, total [as P]010
Flow, in conduit or thru treatment plant300
Flow, process wastewater300
Nitrogen, ammonia total [as N]100
Hardness, total [as CaCO3]100
Nickel, total recoverable100
Zinc, total recoverable100
Aluminum, total recoverable100
Cadmium, total recoverable100
Lead, total recoverable100
Chromium, total recoverable100
Copper, total recoverable100
BOD, 5-day, percent removal100
LC50 Static 48Hr Acute Pimephales promelas100

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

DateWhat EPA recordedAgency
June 30, 2026Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
June 26, 2026Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
April 28, 2025Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
April 30, 2024Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
April 16, 2024Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environmentEP6
March 8, 2024Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
January 29, 2024Dry-weather SSO discharge to waters of the U.S. that may endanger health or the environmentEP6
January 22, 2024Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
May 2, 2023Dry-weather SSO, no discharge to waters of the U.S., not permit compliant, no endangermentEP6
March 16, 2023Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6
August 16, 2022Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environmentEP6

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

Figures from EPA’s ICIS-NPDES download, loaded September 15, 2026.

What this page shows

This public-records page covers Clean Water Act discharge permit NPDES NH0100161 for the Merrimack Waste Water Treatment Plant in Merrimack, NH, a Major Discharger with an administratively continued permit status. The page lists 20 pollutants under a numeric limit and 7 pollutants with an effluent exceedance, with the permit issued September 25, 2007 and expiring November 30, 2012.