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Federal facility (Sewerage Systems), Keystone, South Dakota. NPDES permit SD0021610 expired Jun 30, 2023; its limits still apply. Last 12 months: over a limit once (last February 2026). Source: EPA ECHO, Oct 22, 2026.
| Period ending | Parameter | Reported | Limit | Over by |
|---|---|---|---|---|
| February 2026 | BOD, 5-day, 20 deg. C, daily maximum | 23 mg/L | ≤ 17.5 mg/L | 31% |
| Parameter | Statistic | Limit | Months |
|---|---|---|---|
| Temperature, water deg. centigrade | daily maximum | ≤ 24 deg C | all year |
| Temperature, water deg. centigrade | maximum 7-day average | report only (deg C) | all year |
| Temperature, water deg. centigrade | daily maximum | report only (deg C) | all year |
| Temperature, water deg. centigrade | maximum 7-day average | report only (deg C) | all year |
| Temperature, water deg. centigrade | daily maximum | report only (deg C) | all year |
| Flow rate | 30-day average | report only (MGD) | all year |
| Flow rate | daily maximum | report only (MGD) | all year |
| Conductivity | daily maximum | report only (umho/cm) | all year |
| Oxygen, dissolved [DO] | daily minimum | ≥ 6 mg/L | Apr–Sep |
| Oxygen, dissolved [DO] | daily minimum | ≥ 7 mg/L | Jan, Feb, Mar, Oct, Nov, Dec |
| BOD, 5-day, 20 deg. C | 30-day average | ≤ 10 mg/L | all year |
| BOD, 5-day, 20 deg. C | daily maximum | ≤ 17.5 mg/L | all year |
| BOD, 5-day, 20 deg. C | 30-day average | report only (mg/L) | all year |
| pH | daily minimum | ≥ 6.6 SU | all year |
| pH | daily maximum | ≤ 8.6 SU | all year |
| Alkalinity, total [as CaCO3] | daily maximum | report only (mg/L) | all year |
| Solids, total suspended | 30-day average | ≤ 10 mg/L | all year |
| Solids, total suspended | daily maximum | ≤ 17.5 mg/L | all year |
| Solids, total suspended | 30-day average | report only (mg/L) | all year |
| Oil and grease, hexane extr method | daily maximum | ≤ 10 mg/L | all year |
| Nitrogen, total [as N] | daily maximum | report only (mg/L) | all year |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1.3 mg/L | Jan |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1.3 mg/L | Feb |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 2.2 mg/L | Mar |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1.9 mg/L | Apr |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | May |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | Jun |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | Jul |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | Aug |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | Sep |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1 mg/L | Oct |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1.2 mg/L | Nov |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 1.2 mg/L | Dec |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 2.2 mg/L | Jan |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 2.2 mg/L | Feb |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 4.8 mg/L | Mar |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 4.6 mg/L | Apr |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 1.7 mg/L | May |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 1.7 mg/L | Jun |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 1.7 mg/L | Jul |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 1.7 mg/L | Aug |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 1.7 mg/L | Sep |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 3 mg/L | Oct |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 3.1 mg/L | Nov |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 2.2 mg/L | Dec |
| Phosphorus, total [as P] | daily maximum | report only (mg/L) | all year |
| Arsenic, total recoverable | daily maximum | report only (mg/L) | all year |
| E. coli, colony forming units [CFU] | 30-day geometric mean | ≤ 126 #/100mL | May–Sep |
| E. coli, colony forming units [CFU] | daily maximum | ≤ 235 #/100mL | May–Sep |
| Solids, total dissolved | daily maximum | report only (mg/L) | all year |
| BOD, 5-day, percent removal | monthly average minimum | ≥ 85 % | all year |
| Solids, suspended percent removal | monthly average minimum | ≥ 85 % | all year |
| Oil and grease visual | daily maximum | ≤ 0 abst=0;prst=1 | all year |
Cited limits by parameter: South Dakota's rules and the federal ones.
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On EPA ECHO: Facility report · DMR history
Your permit document is the final word. As JSON: /api/v1/permits/SD0021610 · MCP: https://passage-data.com/mcp