Clean Water Act discharge permit · NPDES MTG580011
TOWN OF DARBY WWTF, Darby, MT: NPDES MTG580011 discharge permit, effluent exceedances, inspections, penalties
- EffectivePermit status
- MinorDischarger class
- 9Pollutants under a numeric limit
- 8Pollutants with an effluent exceedance
TOWN OF DARBY WWTF, held by TOWN OF DARBY, holds NPDES permit MTG580011, which discharges to West Channel Bitterroot River. EPA’s file records it issued December 28, 2017 and expiring December 31, 2022. 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 | TOWN OF DARBY WWTF |
|---|---|
| Permittee as filed | TOWN OF DARBY |
| NPDES ID | MTG580011 |
| Permit status | Effective |
| Permit type | Coverage under a general permit |
| Discharger class | Minor discharger |
| Facility type | Publicly owned treatment works |
| Program | Publicly owned treatment works |
| Issued | December 28, 2017 |
| Expiration date | December 31, 2022 |
| Address | Darby, MT 59829 |
| Receiving water | WEST CHANNEL BITTERROOT RIVER |
| Subwatershed | Bitterroot River-Darby (HUC 170102050806) |
| SIC | 4952 – Sewerage Systems |
Cited to the EPA ICIS-NPDES permit file (ECHO download) and EPA’s NAICS/SIC and component files, the same download.
Effluent limits and exceedances
- 21Pollutants on file
- 9Under a numeric limit
- 20With a violation of any kind
- 8With 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 |
|---|---|---|---|---|---|
| BOD, carbonaceous [5 day, 20 C] | 6 | 25 | 21 | October 31, 2022 | 525% over the limit |
| BOD, 5-day, 20 deg. C | 0 | 30 | 17 | June 30, 2017 | 243% over the limit |
| E. coli, MTEC-MF | 4 | 14 | 14 | October 31, 2023 | 99,999% over the limit |
| Solids, total suspended | 4 | 36 | 12 | June 30, 2025 | 33% over the limit |
| pH | 2 | 15 | 10 | June 30, 2025 | |
| BOD, carbonaceous, percent removal | 1 | 5 | 4 | October 31, 2022 | 91% over the limit |
| BOD, 5-day, percent removal | 0 | 2 | 2 | July 31, 2017 | 140% over the limit |
| Solids, suspended percent removal | 0 | 1 | 1 | July 31, 2017 | 114% over the limit |
| Nitrite + Nitrate total [as N] | 0 | 21 | 0 | ||
| Nitrogen, ammonia total [as N] | 0 | 20 | 0 | ||
| Nitrogen, total [as N] | 0 | 19 | 0 | ||
| Nitrogen, Kjeldahl, total [as N] | 0 | 19 | 0 | ||
| Phosphorus, total [as P] | 0 | 19 | 0 | ||
| Duration of discharge | 1 | 15 | 0 | ||
| Flow rate | 0 | 13 | 0 | ||
| Flow rate | 2 | 2 | 0 | ||
| Oil & Grease | 2 | 2 | 0 | ||
| Coliform, fecal general | 0 | 2 | 0 | ||
| Temperature, water deg. centigrade | 0 | 1 | 0 | ||
| Temperature, water deg. fahrenheit | 0 | 1 | 0 | ||
| Oil and grease visual | 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
- 5Single-event violations
| Date | What EPA recorded | Agency |
|---|---|---|
| December 20, 2022 | Effluent Violations - Numeric effluent violation | ST6 |
| December 20, 2022 | Reporting Violations - Improper/ Incorrect Reporting | ST6 |
| December 20, 2022 | Management Practice Violations - Improper Operation and Maintenance | ST6 |
| October 25, 2019 | Management Practice Violations - Failure to Maintain Records | ST6 |
| October 25, 2019 | 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.
Watch this permit
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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 MTG580011 there.
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Figures from EPA’s ICIS-NPDES download, loaded October 14, 2026.