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Clean Water Act discharge permit · NPDES CT0003921

NAVAL SUB BASE NEW LONDON, Groton, CT: NPDES CT0003921 discharge permit, effluent exceedances, inspections, penalties

NAVAL SUB BASE NEW LONDON, held by NAVAL SUBMARINE BASE NEW LONDO, holds NPDES permit CT0003921, which discharges to Thames River. EPA’s file records it issued September 27, 2006 and expiring September 30, 2011. The status and dates are as EPA’s permit file stood when Velarion loaded it (October 14, 2026); EPA’s free Detailed Facility Report on ECHO carries the permit’s current standing.

Identity

Facility as filedNAVAL SUB BASE NEW LONDON
Permittee as filedNAVAL SUBMARINE BASE NEW LONDO
NPDES IDCT0003921
Permit statusAdministratively continued (past its expiration date and still in force until reissued)
Permit typeIndividual permit
Discharger classMajor discharger
Facility typeFederal facility
IssuedSeptember 27, 2006
Expiration dateSeptember 30, 2011
Issuing agencyCT DEP
AddressGroton, CT 06349
Receiving waterTHAMES RIVER
Receiving water impaired303(D) Listed
SubwatershedThames River-Frontal New London Harbor (HUC 011000030203)
SIC9711 – National Security
Other EPA IDs (FRS)RCRA handler CT4170022020; ICIS-AIR source CT0000000901100628

Cited to the EPA ICIS-NPDES permit file (ECHO download) and EPA’s NAICS/SIC and component files, the same 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
pH25193184March 31, 2025
Flow, maximum during 24 hr period12101100December 31, 202596,994% over the limit
Flow rate28381August 31, 200694,357% over the limit
Copper, total [as Cu]135753August 31, 20101,967% over the limit
Flow124438December 31, 202592,700% over the limit
Temperature, water deg. fahrenheit83330January 31, 202275% over the limit
Oil & Grease82018December 31, 2016690% over the limit
Lead, total [as Pb]131411May 31, 20091,200% over the limit
Zinc, total [as Zn]131310August 31, 2010118% over the limit
LC50 Static 48Hr Acute Americamysis bahia (formerly Mysidopsis bahia)23119June 30, 202273% over the limit
NOAEL Static Renewal 96Hr Acute Menidia sp.355January 31, 2025100% over the limit
Chlorine, total residual444December 31, 2025151% over the limit
Nickel, total [as Ni]963November 30, 200740% over the limit
LC50 Static 96Hr Acute Menidia2043December 31, 202169% over the limit
Solids, total suspended1080
Duration of discharge560
Nitrogen, ammonia total [as N]520
Pass/Fail Static 48Hr Acute Americamysis bahia (formerly Mysidopsis bahia)020
Pass/Fail Static 96 Hr Acute Cyprinodon Variega020
Pass/Fail Static 4 Day Chronic Mysidopsis Bahia020
Pass/Fail Static 4 Day Chronic Cyprinodon Variega020
Iron, total [as Fe]910
Nitrogen, nitrate total [as N]610
Cyclohexylamine410
pH, minimum010
Nitrogen, nitrite total [as N]500
Tin, total [as Sn]500
Flow rate400
Silver, total [as Ag]300
Aluminum, total [as Al]300
Surfactants [MBAS]300
Temp. diff. between intake and discharge300
Rainfall duration100
BOD, 5-day, 20 deg. C100
Oxygen demand, chem. [low level] [COD]100
Nitrogen, Kjeldahl, total [as N]100
Phosphorus, total [as P]100
Cadmium, total [as Cd]100
Chromium, total [as Cr]100
Oxidants, total residual100
Rainfall100

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
September 5, 2019Permit Violations - Discharge Without a Valid PermitST6
September 5, 2019Permit Violations - Violation Specified in CommentST6
September 5, 2019Monitoring Violations - Improper Analysis or Lab ErrorST6

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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Nearby on the register

Figures from EPA’s ICIS-NPDES download, loaded October 14, 2026.

What this page shows

This public-records page covers Clean Water Act discharge permit NPDES CT0003921 for NAVAL SUB BASE NEW LONDON in Groton, CT, which discharges to the Thames River and is administratively continued. The page lists 36 pollutants under a numeric limit and 14 pollutants with an effluent exceedance.