Clean Water Act discharge permit · NPDES MI0020273
SOUTH LYON WWTP, South Lyon, MI: NPDES MI0020273 discharge permit, effluent exceedances, inspections, penalties
- Administratively continuedPermit status
- MajorDischarger class
- 27Pollutants under a numeric limit
- 10Pollutants with an effluent exceedance
- 2Inspections on file
- 0Formal enforcement actions
SOUTH LYON WWTP, held by City of South Lyon, holds NPDES permit MI0020273, which discharges to Yerkes Drain. EPA’s file records it issued January 15, 2015 and expiring October 1, 2018.
SOUTH LYON WWTP, South Lyon, Michigan: Individual permit MI0020273, held by City of South Lyon; Publicly owned treatment works; Administratively continued (past its expiration date and still in force until reissued); issued January 15, 2015, term to October 1, 2018, by State; discharges to Yerkes Drain; Sewage Treatment Facilities.
- Mercury, total [as Hg]: 6 limits, 51 violations of any kind, 23 effluent exceedances, latest December 31, 2011, largest 662% over the limit.
- Phosphorus, total [as P]: 5 limits, 41 violations of any kind, 13 effluent exceedances, latest November 30, 2020, largest 13% over the limit.
- Nitrogen, ammonia total [as N]: 12 limits, 275 violations of any kind, 11 effluent exceedances, latest June 30, 2010, largest 500% over the limit.
- Cyanide [A]: 4 limits, 41 violations of any kind, 5 effluent exceedances, latest April 30, 2009, largest 40% over the limit.
- Toxicity, choice of species: 0 limits, 4 violations of any kind, 4 effluent exceedances, latest April 30, 2026, largest 70% over the limit.
- Coliform, fecal general: 2 limits, 23 violations of any kind, 3 effluent exceedances, latest July 31, 2023, largest 50% over the limit.
- Oxygen, dissolved [DO]: 1 limit, 11 violations of any kind, 2 effluent exceedances, latest September 30, 2012, largest 11% over the limit.
- BOD, carbonaceous [5 day, 20 C]: 8 limits, 37 violations of any kind, 1 effluent exceedance, latest June 30, 2005, largest 2% over the limit.
- Chlorine, total residual: 0 limits, 4 violations of any kind, 1 effluent exceedance, latest April 30, 2005, largest 637% over the limit.
- Toxicity [chronic], Ceriodaphnia dubia: 0 limits, 1 violation of any kind, 1 effluent exceedance, latest January 31, 2006, largest 30% over the limit.
- Barium, total [as Ba]: 2 limits, 88 violations of any kind, 0 effluent exceedances.
- Solids, total suspended: 8 limits, 44 violations of any kind, 0 effluent exceedances.
- Copper, total [as Cu]: 0 limits, 36 violations of any kind, 0 effluent exceedances.
- pH: 2 limits, 18 violations of any kind, 0 effluent exceedances.
- Flow, in conduit or thru treatment plant: 2 limits, 18 violations of any kind, 0 effluent exceedances.
- Toxicity [acute], Ceriodaphnia dubia: 0 limits, 11 violations of any kind, 0 effluent exceedances.
- Solids, total: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Arsenic, dry weight: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Selenium, dry weight: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Copper, dry weight: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Cadmium, dry weight: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Nitrogen, total Kjeldahl: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Molybdenum, sludge, total, dry weight [as Mo]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Zinc, sludge, total, dry weight [as Zn]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Lead, sludge, total, dry weight [as Pb]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Nickel, sludge, total, dry weight [as Ni]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Nitrogen, sludge, total, dry weight [as N]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Mercury, sludge, total, dry weight [as Hg]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Potassium, sludge, total, dry weight [as K]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Phosphorus, sludge, total, dry weight [as P]: 3 limits, 3 violations of any kind, 0 effluent exceedances.
- Solids, suspended percent removal: 2 limits, 2 violations of any kind, 0 effluent exceedances.
- BOD, carb-5 day, 20 deg C, percent removal: 2 limits, 0 violations of any kind, 0 effluent exceedances.
- September 28, 2026: Letter of Violation/ Warning Letter (State).
- September 24, 2026: Evaluation (S).
- June 12, 2026: Notice of Violation (State).
- March 31, 2026: Toxics (S).
- May 16, 2024: Monitoring Violations - Invalid/Unrepresentative Sample (ST6).
- May 16, 2024: Monitoring Violations - Improper Analysis or Lab Error (ST6).
- April 21, 2020: Reporting Violations - Late Submittal of DMRs (ST6).
- April 29, 2019: Management Practice Violations - No Licensed/Certified Operator (ST6).
- April 29, 2019: Management Practice Violations - Improper Operation and Maintenance (ST6).
- April 29, 2019: Monitoring Violations - Failure to Monitor for Non-Toxicity Requirements (ST6).
Michigan holds 200 Publicly owned treatment works coverages of this permit type in EPA’s file; 19 were issued before MI0020273. City of South Lyon holds 2 permits in Michigan.
Other permits held by City of South Lyon
- SOUTH LYON MS4-OAKLAND, South Lyon: MI0059519, issued April 27, 2016
Coverages issued nearest MI0020273
- July 7, 2014: SOUTHERN CLINTON CO WWTP, Dewitt, MI0021008, held by Southern Clinton County Municipal Utilities Authority
- August 5, 2014: MENOMINEE WWTP, Menominee, MI0025631, held by City of Menominee
- September 30, 2014: ST CLAIR WWTP, St. Clair, MI0020591, held by City of St. Clair
- September 30, 2014: BRIGHTON TWP WWTP, Brighton, MI0054968, held by Brighton Township
- October 21, 2014: ST CLAIR RIVER SA WWTP, East China, MI0022845, held by St. Clair River Sewer Authority
- January 21, 2015: MATCH-BE-NASH-SHE-WISH BAND OF POTTAWATOMI INDIANS TRIBAL UTILITY AUTHORITY WWTF, Wayland, MI0058661, held by GUN LAKE GAMING/ENTERTAINMENT
- February 9, 2015: ST JOHNS WWTP, St Johns, MI0026468, held by City of St. Johns
- March 24, 2015: MT PLEASANT WWTP, Mount Pleasant, MI0023655
- March 27, 2015: ST CLAIR COUNTY-ALGONAC WWTP, Algonac, MI0020389, held by St. Clair County, Department of Public Works
- April 3, 2015: IRON MOUNTAIN-KINGSFORD WWTP, Kingsford, MI0023205, held by Iron Mountain/Kingsford Joint Sewage Authority
SOUTH LYON WWTP among its neighbors
EPA’s permit file holds 5 discharge permits in the Inchwagh Lake subwatershed (HUC 040900050109), MI0020273 among them. Its county holds 124, 6 of them major permits; MI0020273 is a major permit.
Other permits in the Inchwagh Lake subwatershed (HUC 040900050109)
- MICH SEAMLESS TUBE LLC, South Lyon: MI0001902, major permit, discharging to Yerkes Drain, permit term to October 1, 2021
- NATIONAL BLOCK COMPANY, South Lyon: MIS410889, minor permit, permit term to April 1, 2029
- SOUTH LYON MS4-OAKLAND, South Lyon: MI0059519, minor permit, permit term to October 1, 2021
- SOUTH LYON PS MS4-OAKLAND, South Lyon: MI0059522, minor permit, permit term to October 1, 2021
Identity
| Facility as filed | SOUTH LYON WWTP |
|---|---|
| Permittee as filed | City of South Lyon |
| NPDES ID | MI0020273 |
| 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 | January 15, 2015 |
| Expiration date | October 1, 2018 |
| Issuing agency | State |
| Address | South Lyon, MI 48178 |
| Receiving water | Yerkes Drain |
| Receiving water impaired | 303(D) Listed |
| Subwatershed | Inchwagh Lake (HUC 040900050109) |
| Program components on file | Biosolids, POTW |
| NAICS | 221320 – Sewage Treatment Facilities |
| SIC | 4952 – Sewerage Systems |
Effluent limits and exceedances
- 32Pollutants on file
- 27Under a numeric limit
- 31With a violation of any kind
- 10With 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 |
|---|---|---|---|---|---|
| Mercury, total [as Hg] | 6 | 51 | 23 | December 31, 2011 | 662% over the limit |
| Phosphorus, total [as P] | 5 | 41 | 13 | November 30, 2020 | 13% over the limit |
| Nitrogen, ammonia total [as N] | 12 | 275 | 11 | June 30, 2010 | 500% over the limit |
| Cyanide [A] | 4 | 41 | 5 | April 30, 2009 | 40% over the limit |
| Toxicity, choice of species | 0 | 4 | 4 | April 30, 2026 | 70% over the limit |
| Coliform, fecal general | 2 | 23 | 3 | July 31, 2023 | 50% over the limit |
| Oxygen, dissolved [DO] | 1 | 11 | 2 | September 30, 2012 | 11% over the limit |
| BOD, carbonaceous [5 day, 20 C] | 8 | 37 | 1 | June 30, 2005 | 2% over the limit |
| Chlorine, total residual | 0 | 4 | 1 | April 30, 2005 | 637% over the limit |
| Toxicity [chronic], Ceriodaphnia dubia | 0 | 1 | 1 | January 31, 2006 | 30% over the limit |
| Barium, total [as Ba] | 2 | 88 | 0 | ||
| Solids, total suspended | 8 | 44 | 0 | ||
| Copper, total [as Cu] | 0 | 36 | 0 | ||
| pH | 2 | 18 | 0 | ||
| Flow, in conduit or thru treatment plant | 2 | 18 | 0 | ||
| Toxicity [acute], Ceriodaphnia dubia | 0 | 11 | 0 | ||
| Solids, total | 3 | 3 | 0 | ||
| Arsenic, dry weight | 3 | 3 | 0 | ||
| Selenium, dry weight | 3 | 3 | 0 | ||
| Copper, dry weight | 3 | 3 | 0 | ||
| Cadmium, dry weight | 3 | 3 | 0 | ||
| Nitrogen, total Kjeldahl | 3 | 3 | 0 | ||
| Molybdenum, sludge, total, dry weight [as Mo] | 3 | 3 | 0 | ||
| Zinc, sludge, total, dry weight [as Zn] | 3 | 3 | 0 | ||
| Lead, sludge, total, dry weight [as Pb] | 3 | 3 | 0 | ||
| Nickel, sludge, total, dry weight [as Ni] | 3 | 3 | 0 | ||
| Nitrogen, sludge, total, dry weight [as N] | 3 | 3 | 0 | ||
| Mercury, sludge, total, dry weight [as Hg] | 3 | 3 | 0 | ||
| Potassium, sludge, total, dry weight [as K] | 3 | 3 | 0 | ||
| Phosphorus, sludge, total, dry weight [as P] | 3 | 3 | 0 | ||
| Solids, suspended percent removal | 2 | 2 | 0 | ||
| BOD, carb-5 day, 20 deg C, percent removal | 2 | 0 | 0 |
Inspections, violations and enforcement
- 6Single-event violations
| Date | What EPA recorded | Agency |
|---|---|---|
| May 16, 2024 | Monitoring Violations - Invalid/Unrepresentative Sample | ST6 |
| May 16, 2024 | Monitoring Violations - Improper Analysis or Lab Error | ST6 |
| April 21, 2020 | Reporting Violations - Late Submittal of DMRs | ST6 |
| April 29, 2019 | Management Practice Violations - No Licensed/Certified Operator | ST6 |
| April 29, 2019 | Management Practice Violations - Improper Operation and Maintenance | ST6 |
| April 29, 2019 | Monitoring Violations - Failure to Monitor for Non-Toxicity Requirements | ST6 |
Inspections
| Date | What EPA recorded | Agency |
|---|---|---|
| September 24, 2026 | Evaluation | S |
| March 31, 2026 | Toxics | S |
Formal enforcement and penalties
0 formal actions, 0 of them with a penalty assessed. Federal and state penalties are separate figures from separate authorities and are shown as each was filed, never added together.
Informal enforcement
| Date | What EPA recorded | Agency |
|---|---|---|
| September 28, 2026 | Letter of Violation/ Warning Letter | State |
| June 12, 2026 | Notice of Violation | State |
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Figures from EPA’s ICIS-NPDES download, loaded October 14, 2026.