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Sewage treatment plant, major discharger, Casper, Wyoming. NPDES permit WY0021920, in force until Oct 31, 2030. Last 12 months: over a limit 8 times (last August 2026). Source: EPA ECHO, Oct 22, 2026.
| Period ending | Parameter | Reported | Limit | Over by |
|---|---|---|---|---|
| January 2026 | Ammonia nitrogen, total, [as N] 30 day, monthly average | 12.74 mg/L | ≤ 10.19 mg/L | 25% |
| January 2026 | BOD, 5-day, 20 deg. C, daily maximum | 106.61 mg/L | ≤ 90 mg/L | 18% |
| January 2026 | BOD, 5-day, 20 deg. C, weekly average | 59.33 mg/L | ≤ 45 mg/L | 32% |
| January 2026 | Solids, total suspended, daily maximum | 103 mg/L | ≤ 90 mg/L | 14% |
| January 2026 | Solids, total suspended, weekly average | 56.5 mg/L | ≤ 45 mg/L | 26% |
| February 2026 | Ammonia nitrogen, total, [as N] 30 day, monthly average | 10.71 mg/L | ≤ 10.19 mg/L | 5% |
| February 2026 | E. coli, daily maximum | 3110 #/100mL | ≤ 2501 #/100mL | 24% |
| August 2026 | E. coli, daily maximum | 850 #/100mL | ≤ 770 #/100mL | 10% |
| Parameter | Statistic | Limit | Months | Outfall |
|---|---|---|---|---|
| Temperature, water deg. centigrade | daily maximum | report only (deg C) | all year | 001 |
| Oxygen, dissolved [DO] | daily maximum | report only (mg/L) | all year | 001 |
| BOD, 5-day, 20 deg. C | monthly average | ≤ 30 mg/L | all year | 001 |
| BOD, 5-day, 20 deg. C | weekly average | ≤ 45 mg/L | all year | 001 |
| BOD, 5-day, 20 deg. C | monthly average | report only (mg/L) | all year | 001 |
| BOD, 5-day, 20 deg. C | weekly average | report only (mg/L) | all year | 001 |
| pH | instantaneous minimum | ≥ 6.5 SU | all year | 001 |
| pH | instantaneous maximum | ≤ 9 SU | all year | 001 |
| Solids, total suspended | monthly average | ≤ 30 mg/L | all year | 001 |
| Solids, total suspended | weekly average | ≤ 45 mg/L | all year | 001 |
| Solids, total suspended | monthly average | report only (mg/L) | all year | 001 |
| Solids, total suspended | weekly 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 | ≤ 12.6 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 5 mg/L | May–Sep | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 31.1 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 17.1 mg/L | May–Sep | 001 |
| Nitrite + Nitrate total [as N] | daily maximum | report only (mg/L) | all year | 001 |
| Phosphorus, total [as P] | daily maximum | report only (mg/L) | all year | 001 |
| Selenium, total [as Se] | daily maximum | report only (ug/L) | all year | 001 |
| Phosphate, ortho [as P] | daily maximum | report only (mg/L) | all year | 001 |
| Chlorine, total residual | monthly average | ≤ .0612 mg/L | May–Sep | 001 |
| Chlorine, total residual | monthly average | ≤ .0618 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| Chlorine, total residual | daily maximum | ≤ .1058 mg/L | May–Sep | 001 |
| Chlorine, total residual | daily maximum | ≤ .1067 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| E. coli | monthly average | ≤ 3306 #/100mL | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| E. coli | monthly average | ≤ 473 #/100mL | May–Sep | 001 |
| E. coli | daily maximum | ≤ 3306 #/100mL | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| E. coli | daily maximum | ≤ 1080 #/100mL | May–Sep | 001 |
| Solids, total dissolved | daily maximum | report only (mg/L) | all year | 001 |
| Flow | daily maximum | report only (MGD) | all year | 001 |
| Flow | monthly average | ≤ 10 MGD | all year | 001 |
| BOD, 5-day, percent removal | monthly average minimum | ≥ 85 % | all year | 001 |
| Solids, suspended percent removal | monthly average minimum | ≥ 85 % | all year | 001 |
| Produced water, oil and grease | daily maximum | ≤ 10 mg/L | all year | 001 |
| Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubia | 7-day maximum | ≤ 0 pass=0;fail=1 | May–Sep | 001 |
| Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubia | 7-day maximum | ≤ 0 pass=0;fail=1 | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| Pass/Fail Static Renewal 7Day Chronic Pimephales promelas | 7-day maximum | ≤ 0 pass=0;fail=1 | May–Sep | 001 |
| Pass/Fail Static Renewal 7Day Chronic Pimephales promelas | 7-day maximum | ≤ 0 pass=0;fail=1 | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 001 |
| Temperature, water deg. centigrade | daily maximum | report only (deg C) | all year | 002 |
| Oxygen, dissolved [DO] | daily maximum | report only (mg/L) | all year | 002 |
| 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 |
| BOD, 5-day, 20 deg. C | monthly average | report only (mg/L) | all year | 002 |
| BOD, 5-day, 20 deg. C | weekly average | report only (mg/L) | all year | 002 |
| pH | instantaneous minimum | ≥ 6.5 SU | all year | 002 |
| pH | instantaneous 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 |
| Solids, total suspended | monthly average | report only (mg/L) | all year | 002 |
| Solids, total suspended | weekly average | report only (mg/L) | all year | 002 |
| Nitrogen, total [as N] | daily maximum | report only (mg/L) | all year | 002 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 12.6 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Nitrogen, ammonia total [as N] | monthly average | ≤ 5 mg/L | May–Sep | 002 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 31.1 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 17.1 mg/L | May–Sep | 002 |
| Nitrite + Nitrate total [as N] | daily maximum | report only (mg/L) | all year | 002 |
| Phosphorus, total [as P] | daily maximum | report only (mg/L) | all year | 002 |
| Selenium, total [as Se] | daily maximum | report only (ug/L) | all year | 002 |
| Phosphate, ortho [as P] | daily maximum | report only (mg/L) | all year | 002 |
| Chlorine, total residual | monthly average | ≤ .0612 mg/L | May–Sep | 002 |
| Chlorine, total residual | monthly average | ≤ .0618 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Chlorine, total residual | daily maximum | ≤ .1058 mg/L | May–Sep | 002 |
| Chlorine, total residual | daily maximum | ≤ .1067 mg/L | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| E. coli | monthly average | ≤ 473 #/100mL | May–Sep | 002 |
| E. coli | monthly average | ≤ 3306 #/100mL | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| E. coli | daily maximum | ≤ 1080 #/100mL | May–Sep | 002 |
| E. coli | daily maximum | ≤ 3306 #/100mL | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Solids, total dissolved | daily maximum | report only (mg/L) | all year | 002 |
| Flow | daily maximum | report only (MGD) | all year | 002 |
| Flow | monthly average | ≤ 10 MGD | all year | 002 |
| BOD, 5-day, percent removal | monthly average minimum | ≥ 85 % | all year | 002 |
| Solids, suspended percent removal | monthly average minimum | ≥ 85 % | all year | 002 |
| Produced water, oil and grease | daily maximum | ≤ 10 mg/L | all year | 002 |
| Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubia | 7-day maximum | ≤ 0 pass=0;fail=1 | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubia | 7-day maximum | ≤ 0 pass=0;fail=1 | May–Sep | 002 |
| Pass/Fail Static Renewal 7Day Chronic Pimephales promelas | 7-day maximum | ≤ 0 pass=0;fail=1 | Jan, Feb, Mar, Apr, Oct, Nov, Dec | 002 |
| Pass/Fail Static Renewal 7Day Chronic Pimephales promelas | 7-day maximum | ≤ 0 pass=0;fail=1 | May–Sep | 002 |
| Temperature, water deg. centigrade | daily maximum | report only (deg C) | all year | DMP1 |
| pH | instantaneous minimum | report only (SU) | all year | DMP1 |
| pH | instantaneous maximum | report only (SU) | all year | DMP1 |
Cited limits by parameter: Wyoming's rules and the federal ones.
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On EPA ECHO: Facility report · DMR history
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