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Sewage treatment plant, major discharger, South Lyon, Michigan. NPDES permit MI0020273, in force until Oct 1, 2028. Last 12 months: over a limit once (last April 2026). Source: EPA ECHO, Oct 22, 2026.
| Period ending | Parameter | Reported | Limit | Over by |
|---|---|---|---|---|
| April 2026 | Toxicity, choice of species, value | 1.4 | ≤ 1 tox chronic | 40% |
| Parameter | Statistic | Limit | Months | Outfall |
|---|---|---|---|---|
| Oxygen, dissolved [DO] | daily minimum | ≥ 7 mg/L | all year | 001 |
| pH | daily minimum | ≥ 6.5 SU | all year | 001 |
| pH | daily maximum | ≤ 9 SU | all year | 001 |
| Solids, total suspended | monthly average | ≤ 30 mg/L | Jan, Feb, Mar, Dec | 001 |
| Solids, total suspended | monthly average | ≤ 20 mg/L | Apr–Nov | 001 |
| Solids, total suspended | 7-day average | ≤ 45 mg/L | Jan, Feb, Mar, Dec | 001 |
| Solids, total suspended | 7-day average | ≤ 30 mg/L | Apr–Nov | 001 |
| Solids, total suspended | monthly average | ≤ 630 lb/d | Jan, Feb, Mar, Dec | 001 |
| Solids, total suspended | monthly average | ≤ 420 lb/d | Apr–Nov | 001 |
| Solids, total suspended | 7-day average | ≤ 940 lb/d | Jan, Feb, Mar, Dec | 001 |
| Solids, total suspended | 7-day average | ≤ 630 lb/d | Apr–Nov | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 7.3 mg/L | Jan, Feb, Mar, Dec | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ .5 mg/L | May–Nov | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 4.2 mg/L | Apr | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 10 mg/L | Jan, Feb, Mar, Dec | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 2 mg/L | May–Nov | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 4.6 mg/L | Apr | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 150 lb/d | Jan, Feb, Mar, Dec | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 10 lb/d | May–Nov | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 88 lb/d | Apr | 001 |
| Nitrogen, ammonia total [as N] | 7-day average | ≤ 210 lb/d | Jan, Feb, Mar, Dec | 001 |
| Nitrogen, ammonia total [as N] | 7-day average | ≤ 42 lb/d | May–Nov | 001 |
| Nitrogen, ammonia total [as N] | 7-day average | ≤ 96 lb/d | Apr | 001 |
| Phosphorus, total [as P] | monthly average | ≤ .3 mg/L | all year | 001 |
| Phosphorus, total [as P] | daily maximum | report only (mg/L) | all year | 001 |
| Phosphorus, total [as P] | monthly average | ≤ 6.3 lb/d | all year | 001 |
| Phosphorus, total [as P] | daily maximum | report only (lb/d) | all year | 001 |
| Phosphorus, total [as P] | annual maximum | ≤ 800 lb/yr | all year | 001 |
| Phosphorus, total [as P] | monthly average | report only (lb/mo) | all year | 001 |
| Chloride [as Cl] | daily maximum | report only (mg/L) | all year | 001 |
| Sulfate, total [as SO4] | daily maximum | report only (mg/L) | all year | 001 |
| Selenium, total [as Se] | monthly average | ≤ 5 ug/L | all year | 001 |
| Selenium, total [as Se] | daily maximum | report only (ug/L) | all year | 001 |
| Selenium, total [as Se] | monthly average | ≤ .1 lb/d | all year | 001 |
| Selenium, total [as Se] | daily maximum | report only (lb/d) | all year | 001 |
| Toxicity, choice of species | value | ≤ 1 tox chronic | all year | 001 |
| Flow, in conduit or thru treatment plant | monthly average | report only (MGD) | all year | 001 |
| Flow, in conduit or thru treatment plant | daily maximum | report only (MGD) | all year | 001 |
| Perfluorooctanesulfonate | daily maximum | report only (ng/L) | all year | 001 |
| Toxicity [acute], Ceriodaphnia dubia | daily maximum | ≤ 1 tox acute | all year | 001 |
| Mercury, total [as Hg] | monthly average | report only (ng/L) | all year | 001 |
| Mercury, total [as Hg] | daily maximum | report only (ng/L) | all year | 001 |
| Mercury, total [as Hg] | monthly average | report only (lb/d) | all year | 001 |
| Mercury, total [as Hg] | daily maximum | report only (lb/d) | all year | 001 |
| Coliform, fecal general | monthly geometric mean | ≤ 200 #/100mL | all year | 001 |
| Coliform, fecal general | 7-day geometric mean | ≤ 400 #/100mL | all year | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 4 mg/L | Apr–Nov | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 23 mg/L | Jan, Feb, Mar, Dec | 001 |
| BOD, carbonaceous [5 day, 20 C] | daily maximum | ≤ 10 mg/L | Apr–Nov | 001 |
| BOD, carbonaceous [5 day, 20 C] | daily maximum | ≤ 35 mg/L | Jan, Feb, Mar, Dec | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 83 lb/d | Apr–Nov | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 480 lb/d | Jan, Feb, Mar, Dec | 001 |
| BOD, carbonaceous [5 day, 20 C] | 7-day average | ≤ 210 lb/d | Apr–Nov | 001 |
| BOD, carbonaceous [5 day, 20 C] | 7-day average | ≤ 730 lb/d | Jan, Feb, Mar, Dec | 001 |
| BOD, carb-5 day, 20 deg C, percent removal | minimum | ≥ 85 % | Jan, Feb, Mar, Dec | 001 |
| BOD, carb-5 day, 20 deg C, percent removal | daily minimum | report only (%) | Jan, Feb, Mar, Dec | 001 |
| Solids, suspended percent removal | minimum | ≥ 85 % | Jan, Feb, Mar, Dec | 001 |
| Solids, suspended percent removal | daily minimum | report only (%) | Jan, Feb, Mar, Dec | 001 |
| TU Static 24 Hr Acute Pimephales promelas | daily maximum | ≤ 1 tox acute | all year | 001 |
| Static 48 Hr Chronic Pimphales Promelas | value | ≤ 1 tox chronic | all year | 001 |
| Solids, total | monthly minimum | report only (%) | all year | SLD |
| Solids, total | monthly average | report only (%) | all year | SLD |
| Solids, total | monthly maximum | report only (%) | all year | SLD |
| Arsenic, dry weight | monthly minimum | report only (mg/kg) | all year | SLD |
| Arsenic, dry weight | monthly average | report only (mg/kg) | all year | SLD |
| Arsenic, dry weight | monthly maximum | ≤ 75 mg/kg | all year | SLD |
| Selenium, dry weight | monthly minimum | report only (mg/kg) | all year | SLD |
| Selenium, dry weight | monthly average | report only (mg/kg) | all year | SLD |
| Selenium, dry weight | monthly maximum | ≤ 100 mg/kg | all year | SLD |
| Copper, dry weight | monthly minimum | report only (mg/kg) | all year | SLD |
| Copper, dry weight | monthly average | report only (mg/kg) | all year | SLD |
| Copper, dry weight | monthly maximum | ≤ 4300 mg/kg | all year | SLD |
| Cadmium, dry weight | monthly minimum | report only (mg/kg) | all year | SLD |
| Cadmium, dry weight | monthly average | report only (mg/kg) | all year | SLD |
| Cadmium, dry weight | monthly maximum | ≤ 85 mg/kg | all year | SLD |
| Nitrogen, total Kjeldahl | monthly minimum | report only (mg/kg) | all year | SLD |
| Nitrogen, total Kjeldahl | monthly average | report only (mg/kg) | all year | SLD |
| Nitrogen, total Kjeldahl | monthly maximum | report only (mg/kg) | all year | SLD |
| Molybdenum, sludge, total, dry weight [as Mo] | monthly minimum | report only (mg/kg) | all year | SLD |
| Molybdenum, sludge, total, dry weight [as Mo] | monthly average | report only (mg/kg) | all year | SLD |
| Molybdenum, sludge, total, dry weight [as Mo] | monthly maximum | ≤ 75 mg/kg | all year | SLD |
| Zinc, sludge, total, dry weight [as Zn] | monthly minimum | report only (mg/kg) | all year | SLD |
| Zinc, sludge, total, dry weight [as Zn] | monthly average | report only (mg/kg) | all year | SLD |
| Zinc, sludge, total, dry weight [as Zn] | monthly maximum | ≤ 7500 mg/kg | all year | SLD |
| Lead, sludge, total, dry weight [as Pb] | monthly minimum | report only (mg/kg) | all year | SLD |
| Lead, sludge, total, dry weight [as Pb] | monthly average | report only (mg/kg) | all year | SLD |
| Lead, sludge, total, dry weight [as Pb] | monthly maximum | ≤ 840 mg/kg | all year | SLD |
| Nickel, sludge, total, dry weight [as Ni] | monthly minimum | report only (mg/kg) | all year | SLD |
| Nickel, sludge, total, dry weight [as Ni] | monthly average | report only (mg/kg) | all year | SLD |
| Nickel, sludge, total, dry weight [as Ni] | monthly maximum | ≤ 420 mg/kg | all year | SLD |
| Nitrogen, sludge, total, dry weight [as N] | monthly minimum | report only (mg/kg) | all year | SLD |
| Nitrogen, sludge, total, dry weight [as N] | monthly average | report only (mg/kg) | all year | SLD |
| Nitrogen, sludge, total, dry weight [as N] | monthly maximum | report only (mg/kg) | all year | SLD |
| Mercury, sludge, total, dry weight [as Hg] | monthly minimum | report only (mg/kg) | all year | SLD |
| Mercury, sludge, total, dry weight [as Hg] | monthly average | report only (mg/kg) | all year | SLD |
| Mercury, sludge, total, dry weight [as Hg] | monthly maximum | ≤ 57 mg/kg | all year | SLD |
| Potassium, sludge, total, dry weight [as K] | monthly minimum | report only (mg/kg) | all year | SLD |
| Potassium, sludge, total, dry weight [as K] | monthly average | report only (mg/kg) | all year | SLD |
| Potassium, sludge, total, dry weight [as K] | monthly maximum | report only (mg/kg) | all year | SLD |
| Phosphorus, sludge, total, dry weight [as P] | monthly minimum | report only (mg/kg) | all year | SLD |
| Phosphorus, sludge, total, dry weight [as P] | monthly average | report only (mg/kg) | all year | SLD |
| Phosphorus, sludge, total, dry weight [as P] | monthly maximum | report only (mg/kg) | all year | SLD |
| Parameter | New limit | New or tighter | Median, last 12 months | × new limit |
|---|---|---|---|---|
| Nitrogen, ammonia total [as N], monthly average | 1.7 mg/L (Jan, Feb, Mar, Dec) | tighter | 0.06 mg/L (4 values) | 0.0353× |
| Nitrogen, ammonia total [as N], monthly average | 35 lb/d (Jan, Feb, Mar, Dec) | tighter | 0.666 lb/d (4 values) | 0.019× |
| Nitrogen, ammonia total [as N], monthly average | 25 lb/d (Apr) | tighter | — | — |
| Nitrogen, ammonia total [as N], monthly average | 1.2 mg/L (Apr) | tighter | — | — |
Cited limits by parameter: Michigan's rules and the federal ones.
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Your permit document is the final word. As JSON: /api/v1/permits/MI0020273 · MCP: https://passage-data.com/mcp