Clean Water Act discharge permit · NPDES CT0003263
MILLSTONE POWER STATION, Waterford, CT: NPDES CT0003263 discharge permit, effluent exceedances, inspections, penalties
- Administratively continuedPermit status
- MajorDischarger class
- 37Pollutants under a numeric limit
- 14Pollutants with an effluent exceedance
MILLSTONE POWER STATION holds NPDES permit CT0003263, which discharges to Long Island Sound. EPA’s file records it issued December 14, 1992 and expiring December 13, 1997. 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 filed | MILLSTONE POWER STATION |
|---|---|
| Permittee as filed | MILLSTONE POWER STATION |
| NPDES ID | CT0003263 |
| Permit status | Administratively continued (past its expiration date and still in force until reissued) |
| Permit type | Individual permit |
| Discharger class | Major discharger |
| Facility type | Not a publicly owned treatment works |
| Issued | December 14, 1992 |
| Expiration date | December 13, 1997 |
| Issuing agency | CT DEP |
| Address | Waterford, CT 06385 |
| Receiving water | LONG ISLAND SOUND |
| Receiving water impaired | 303(D) Listed |
| Subwatershed | Niantic River (HUC 011000030304) |
| SIC | 4911 – Electric Services |
| Other EPA IDs (FRS) | RCRA handler CTD000845198; ICIS-AIR source CT0000000901100173 |
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
- 49Pollutants on file
- 37Under a numeric limit
- 27With a violation of any kind
- 14With 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 |
|---|---|---|---|---|---|
| Flow, in conduit or thru treatment plant | 10 | 48 | 48 | October 31, 1999 | 5,614% over the limit |
| Solids, total suspended | 31 | 29 | 23 | October 31, 2024 | 832% over the limit |
| Chlorine, free available | 12 | 14 | 14 | September 30, 2010 | 17,180% over the limit |
| Flow, gallons/batch | 19 | 14 | 12 | August 31, 2010 | 136% over the limit |
| Chlorine, total residual | 3 | 12 | 12 | October 31, 2010 | 2,900% over the limit |
| pH | 27 | 18 | 10 | November 30, 2014 | |
| Temp. diff. between samp. & upstrm deg. F | 12 | 11 | 6 | November 30, 1999 | 110% over the limit |
| Boric acid | 11 | 9 | 6 | June 30, 2000 | 700% over the limit |
| Zinc, total [as Zn] | 11 | 4 | 4 | June 30, 1997 | 171% over the limit |
| Oil & Grease | 20 | 8 | 3 | April 30, 2005 | 71,900% over the limit |
| Temperature, water deg. fahrenheit | 26 | 5 | 2 | July 31, 2010 | 20% over the limit |
| Copper, total [as Cu] | 11 | 2 | 2 | June 30, 1997 | 14% over the limit |
| pH, maximum | 0 | 2 | 2 | March 31, 2016 | |
| Hydrazine | 10 | 9 | 1 | March 31, 1997 | 23% over the limit |
| Boron, total | 0 | 8 | 0 | ||
| Nitrogen, ammonia total [as N] | 6 | 7 | 0 | ||
| Ethanolamine | 0 | 3 | 0 | ||
| Flow rate | 8 | 2 | 0 | ||
| Nitrogen, Kjeldahl, total [as N] | 0 | 2 | 0 | ||
| Dichlorodifluoromethane | 0 | 2 | 0 | ||
| Chlorodifluoromethane | 0 | 2 | 0 | ||
| Flow, maximum during 24 hr period | 0 | 2 | 0 | ||
| Surfactants, anionic | 0 | 2 | 0 | ||
| Turbidity | 0 | 1 | 0 | ||
| Molybdenum, total [as Mo] | 0 | 1 | 0 | ||
| LC50 Static 48Hr Acute Americamysis bahia (formerly Mysidopsis bahia) | 0 | 1 | 0 | ||
| LC50 Static 48Hr Acute Cyprinodon variegatus | 0 | 1 | 0 | ||
| Lead, total [as Pb] | 11 | 0 | 0 | ||
| Nickel, total [as Ni] | 11 | 0 | 0 | ||
| Thermal Discharge | 8 | 0 | 0 | ||
| Pass/Fail Static 48Hr Acute Americamysis bahia (formerly Mysidopsis bahia) | 8 | 0 | 0 | ||
| Pass/Fail Static 4 Day Chronic Mysidopsis Bahia | 8 | 0 | 0 | ||
| Surfactants [MBAS] | 6 | 0 | 0 | ||
| Pass/Fail Static 96 Hr Acute Cyprinodon Variega | 6 | 0 | 0 | ||
| Pass/Fail Static 4 Day Chronic Cyprinodon Variega | 6 | 0 | 0 | ||
| Iron, total [as Fe] | 5 | 0 | 0 | ||
| BOD, 5-day, 20 deg. C | 3 | 0 | 0 | ||
| Oxygen demand, chem. [low level] [COD] | 3 | 0 | 0 | ||
| Cadmium, total [as Cd] | 3 | 0 | 0 | ||
| Chromium, total [as Cr] | 3 | 0 | 0 | ||
| Specific conductance | 2 | 0 | 0 | ||
| Hydrogen peroxide | 2 | 0 | 0 | ||
| Freon, total | 2 | 0 | 0 | ||
| Formic acid | 2 | 0 | 0 | ||
| Oxalic acid | 2 | 0 | 0 | ||
| Citric acid | 2 | 0 | 0 | ||
| EDTA | 2 | 0 | 0 | ||
| Beryllium, total recoverable [as Be] | 1 | 0 | 0 | ||
| Lithium, total [as Li] | 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
- 4Single-event violations
| Date | What EPA recorded | Agency |
|---|---|---|
| July 24, 2024 | Monitoring Violations - Invalid/Unrepresentative Sample | ST6 |
| July 24, 2024 | Permit Violations - Violation Specified in Comment | ST6 |
| April 14, 2022 | Monitoring Violations - Invalid/Unrepresentative Sample | ST6 |
| April 14, 2022 | Monitoring Violations - Improper Analysis or Lab Error | ST6 |
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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Figures from EPA’s ICIS-NPDES download, loaded October 14, 2026.