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Sewage treatment plant, Tiffin, Iowa. NPDES permit IA0036617, in force until Jun 30, 2030. Last 12 months: over a limit 2 times (last January 2026), 1 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.
| Period ending | Parameter | Reported | Limit | Over by |
|---|---|---|---|---|
| December 2025 | Oxygen, dissolved [DO], daily minimum | 2.57 | ≥ 4.3 mg/L | 40% |
| January 2026 | Oxygen, dissolved [DO], daily minimum | 2.27 | ≥ 4.3 mg/L | 47% |
| Parameter | Statistic | Limit | Months |
|---|---|---|---|
| Oxygen, dissolved [DO] | daily minimum | ≥ 4.3 mg/L | all year |
| BOD, 5-day, 20 deg. C | 30-day average | report only (mg/L) | all year |
| BOD, 5-day, 20 deg. C | daily maximum | report only (mg/L) | all year |
| BOD, 5-day, 20 deg. C | 30-day average | report only (lb/d) | all year |
| BOD, 5-day, 20 deg. C | daily maximum | report only (lb/d) | all year |
| pH | daily minimum | ≥ 6 SU | all year |
| pH | daily maximum | ≤ 9 SU | all year |
| pH | 30-day average | report only (SU) | all year |
| pH | daily maximum | report only (SU) | all year |
| Solids, total suspended | 30-day average | ≤ 30 mg/L | all year |
| Solids, total suspended | 7-day average | ≤ 45 mg/L | all year |
| Solids, total suspended | 30-day average | ≤ 244 lb/d | all year |
| Solids, total suspended | 7-day average | ≤ 366 lb/d | all year |
| Solids, total suspended | 30-day average | report only (mg/L) | all year |
| Solids, total suspended | daily maximum | report only (mg/L) | all year |
| Solids, total suspended | 30-day average | report only (lb/d) | all year |
| Solids, total suspended | daily maximum | report only (lb/d) | all year |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 8.8 mg/L | Feb |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 2.9 mg/L | Jun |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 3.4 mg/L | Apr |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 2.4 mg/L | Sep |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 7.6 mg/L | Mar |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.2 mg/L | Nov |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 7.7 mg/L | Jan |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 3.5 mg/L | Oct |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 3.9 mg/L | May |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.6 mg/L | Dec |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 2.3 mg/L | Jul |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 2.1 mg/L | Aug |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 14.6 mg/L | Feb |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 14.8 mg/L | Jun |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16 mg/L | Apr |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16.8 mg/L | Sep |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 15 mg/L | Mar |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 15 mg/L | Nov |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 15.5 mg/L | Jan |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16 mg/L | Oct |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 15.5 mg/L | May |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16.3 mg/L | Dec |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 18 mg/L | Jul |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16.6 mg/L | Aug |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 57.5 lb/d | Feb |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 19.1 lb/d | Jun |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 22.2 lb/d | Apr |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 15.4 lb/d | Sep |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 49.2 lb/d | Mar |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 33.9 lb/d | Nov |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 49.8 lb/d | Jan |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 22.7 lb/d | Oct |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 25.3 lb/d | May |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 36.1 lb/d | Dec |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 14.6 lb/d | Jul |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 13.9 lb/d | Aug |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 117.4 lb/d | Feb |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 119.2 lb/d | Jun |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 129.3 lb/d | Apr |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 136 lb/d | Sep |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 121.2 lb/d | Mar |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 121 lb/d | Nov |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 125.4 lb/d | Jan |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 129.4 lb/d | Oct |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 125.3 lb/d | May |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 131.4 lb/d | Dec |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 145.2 lb/d | Jul |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 134 lb/d | Aug |
| Nitrogen, Kjeldahl, total [as N] | 30-day average | report only (mg/L) | all year |
| Nitrogen, Kjeldahl, total [as N] | daily maximum | report only (mg/L) | all year |
| Nitrogen, Kjeldahl, total [as N] | 30-day average | report only (lb/d) | all year |
| Nitrogen, Kjeldahl, total [as N] | daily maximum | report only (lb/d) | all year |
| E. coli | geometric mean | ≤ 127 #/100mL | Mar–Nov |
| BOD, carbonaceous [5 day, 20 C] | 30-day average | ≤ 25 mg/L | all year |
| BOD, carbonaceous [5 day, 20 C] | 7-day average | ≤ 40 mg/L | all year |
| BOD, carbonaceous [5 day, 20 C] | 30-day average | ≤ 203 lb/d | all year |
| BOD, carbonaceous [5 day, 20 C] | 7-day average | ≤ 325 lb/d | all year |
Cited limits by parameter: Iowa's rules and the federal ones.
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