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Sewage treatment plant, major discharger, O'fallon, Illinois. NPDES permit IL0021083, in force until Nov 30, 2026. Last 12 months: over a limit 2 times (last July 2026), 3 of 34 reports late. Source: EPA ECHO, Oct 22, 2026.
| Period ending | Parameter | Reported | Limit | Over by |
|---|---|---|---|---|
| February 2026 | Zinc, total [as Zn], monthly average | .0433 mg/L | ≤ .0384 mg/L | 13% |
| July 2026 | Phosphorus, total [as P], monthly average | 1.04 mg/L | ≤ 1 mg/L | 4% |
| Parameter | Statistic | Limit | Months | Outfall |
|---|---|---|---|---|
| Oxygen, dissolved [DO] | monthly average minimum | ≥ 5.5 mg/L | Jan, Feb, Aug, Sep, Oct, Nov, Dec | 001 |
| Oxygen, dissolved [DO] | minimum weekly average | ≥ 4 mg/L | Jan, Feb, Aug, Sep, Oct, Nov, Dec | 001 |
| Oxygen, dissolved [DO] | minimum weekly average | ≥ 6 mg/L | Mar–Jul | 001 |
| Oxygen, dissolved [DO] | daily minimum | ≥ 3.5 mg/L | Jan, Feb, Aug, Sep, Oct, Nov, Dec | 001 |
| Oxygen, dissolved [DO] | daily minimum | ≥ 5 mg/L | Mar–Jul | 001 |
| pH | minimum | ≥ 6 SU | all year | 001 |
| pH | maximum | ≤ 9 SU | all year | 001 |
| Solids, total suspended | monthly average | ≤ 12 mg/L | all year | 001 |
| Solids, total suspended | daily maximum | ≤ 24 mg/L | all year | 001 |
| Solids, total suspended | monthly average | ≤ 1140 lb/d | all year | 001 |
| Solids, total suspended | daily maximum | ≤ 2280 lb/d | all year | 001 |
| Oil & Grease | daily maximum | report only (mg/L) | all year | 001 |
| Oil & Grease | daily maximum | report only (mg/L) | all year | 001 |
| Nitrogen, total [as N] | monthly average | report only (mg/L) | all year | 001 |
| Nitrogen, total [as N] | daily maximum | report only (mg/L) | all year | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 1.6 mg/L | Mar | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 1.5 mg/L | Apr–Oct | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 3.6 mg/L | Jan, Feb, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 7.2 mg/L | Mar | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 3 mg/L | Apr–Oct | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 6.9 mg/L | Jan, Feb, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 152 lb/d | Mar | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 142 lb/d | Apr–Oct | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 342 lb/d | Jan, Feb, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 684 lb/d | Mar | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 285 lb/d | Apr–Oct | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 655 lb/d | Jan, Feb, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | weekly average | ≤ 4 mg/L | Mar | 001 |
| Nitrogen, ammonia total [as N] | weekly average | ≤ 380 lb/d | Mar | 001 |
| Phosphorus, total [as P] | monthly average | ≤ 1 mg/L | all year | 001 |
| Phosphorus, total [as P] | monthly average | ≤ 95 lb/d | all year | 001 |
| Cyanide, total [as CN] | daily maximum | report only (ug/L) | all year | 001 |
| Cyanide, total [as CN] | daily maximum | report only (ug/L) | all year | 001 |
| Cyanide, free [amenable to chlorination] | daily maximum | report only (ug/L) | all year | 001 |
| Cyanide, free [amenable to chlorination] | daily maximum | report only (ug/L) | all year | 001 |
| Fluoride, total [as F] | daily maximum | report only (mg/L) | all year | 001 |
| Fluoride, total [as F] | daily maximum | report only (mg/L) | all year | 001 |
| Arsenic, total [as As] | daily maximum | report only (mg/L) | all year | 001 |
| Arsenic, total [as As] | daily maximum | report only (mg/L) | all year | 001 |
| Barium, total [as Ba] | daily maximum | report only (mg/L) | all year | 001 |
| Barium, total [as Ba] | daily maximum | report only (mg/L) | all year | 001 |
| Cadmium, total [as Cd] | daily maximum | report only (mg/L) | all year | 001 |
| Cadmium, total [as Cd] | daily maximum | report only (mg/L) | all year | 001 |
| Chromium, hexavalent [as Cr] | daily maximum | report only (mg/L) | all year | 001 |
| Chromium, hexavalent [as Cr] | daily maximum | report only (mg/L) | all year | 001 |
| Chromium, total [as Cr] | daily maximum | report only (mg/L) | all year | 001 |
| Chromium, total [as Cr] | daily maximum | report only (mg/L) | all year | 001 |
| Copper, total [as Cu] | daily maximum | report only (mg/L) | all year | 001 |
| Copper, total [as Cu] | daily maximum | report only (mg/L) | all year | 001 |
| Iron, total [as Fe] | daily maximum | report only (mg/L) | all year | 001 |
| Iron, total [as Fe] | daily maximum | report only (mg/L) | all year | 001 |
| Iron, dissolved [as Fe] | daily maximum | report only (mg/L) | all year | 001 |
| Iron, dissolved [as Fe] | daily maximum | report only (mg/L) | all year | 001 |
| Lead, total [as Pb] | daily maximum | report only (mg/L) | all year | 001 |
| Lead, total [as Pb] | daily maximum | report only (mg/L) | all year | 001 |
| Manganese, total [as Mn] | daily maximum | report only (mg/L) | all year | 001 |
| Manganese, total [as Mn] | daily maximum | report only (mg/L) | all year | 001 |
| Nickel, total [as Ni] | daily maximum | report only (mg/L) | all year | 001 |
| Nickel, total [as Ni] | daily maximum | report only (mg/L) | all year | 001 |
| Silver, total [as Ag] | daily maximum | report only (mg/L) | all year | 001 |
| Silver, total [as Ag] | daily maximum | report only (mg/L) | all year | 001 |
| Zinc, total [as Zn] | monthly average | ≤ .0384 mg/L | all year | 001 |
| Zinc, total [as Zn] | daily maximum | report only (mg/L) | all year | 001 |
| Zinc, total [as Zn] | daily maximum | report only (mg/L) | all year | 001 |
| Zinc, total [as Zn] | monthly average | ≤ 3.65 lb/d | all year | 001 |
| Selenium, total [as Se] | daily maximum | report only (mg/L) | all year | 001 |
| Selenium, total [as Se] | daily maximum | report only (mg/L) | all year | 001 |
| Phenolics, total recoverable | daily maximum | report only (mg/L) | all year | 001 |
| Phenolics, total recoverable | daily maximum | report only (mg/L) | 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 |
| Chlorine, total residual | daily maximum | ≤ .038 mg/L | all year | 001 |
| Mercury, total [as Hg] | daily maximum | report only (ng/L) | all year | 001 |
| Mercury, total [as Hg] | daily maximum | report only (ng/L) | all year | 001 |
| Coliform, fecal general | daily maximum | ≤ 400 #/100mL | May–Oct | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 10 mg/L | all year | 001 |
| BOD, carbonaceous [5 day, 20 C] | daily maximum | ≤ 20 mg/L | all year | 001 |
| BOD, carbonaceous [5 day, 20 C] | monthly average | ≤ 950 lb/d | all year | 001 |
| BOD, carbonaceous [5 day, 20 C] | daily maximum | ≤ 1900 lb/d | all year | 001 |
| BOD, 5-day, 20 deg. C | monthly average | ≤ 30 mg/L | all year | 002 |
| BOD, 5-day, 20 deg. C | weekly average | ≤ 45 mg/L | all year | 002 |
| pH | minimum | ≥ 6 SU | all year | 002 |
| pH | maximum | ≤ 9 SU | all year | 002 |
| Solids, total suspended | monthly average | ≤ 30 mg/L | all year | 002 |
| Solids, total suspended | weekly average | ≤ 45 mg/L | all year | 002 |
| Nitrogen, ammonia total [as N] | monthly average | report only (mg/L) | all year | 002 |
| Phosphorus, total [as P] | monthly average | report only (mg/L) | all year | 002 |
| Chlorine, total residual | monthly average | ≤ .75 mg/L | all year | 002 |
| Coliform, fecal general | daily maximum | ≤ 400 #/100mL | all year | 002 |
| Flow, total | monthly total | report only (Mgal/mo) | all year | 002 |
| BOD, 5-day, 20 deg. C | monthly average | report only (mg/L) | all year | INF |
| Solids, total suspended | monthly average | report only (mg/L) | all year | INF |
| Flow, in conduit or thru treatment plant | monthly average | report only (MGD) | all year | INF |
| Flow, in conduit or thru treatment plant | daily maximum | report only (MGD) | all year | INF |
Cited limits by parameter: Illinois's rules and the federal ones.
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On EPA ECHO: Facility report · DMR history
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