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Sewage treatment plant, Walden, Colorado. NPDES permit CO0020788 expired Aug 31, 2020; its limits still apply. Last 12 months: no values over a limit, 2 of 25 reports late. Source: EPA ECHO, Oct 22, 2026.
| Parameter | Statistic | Limit | Months | Outfall |
|---|---|---|---|---|
| BOD, 5-day, 20 deg. C | 30-day average | ≤ 30 mg/L | all year | 001 |
| BOD, 5-day, 20 deg. C | maximum 7-day average | ≤ 45 mg/L | all year | 001 |
| pH | minimum | ≥ 6.5 SU | all year | 001 |
| pH | maximum | ≤ 9 SU | all year | 001 |
| Solids, total suspended | 30-day average | ≤ 30 mg/L | all year | 001 |
| Solids, total suspended | maximum 7-day average | ≤ 45 mg/L | all year | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 4.6 mg/L | Apr | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.8 mg/L | Jan | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.8 mg/L | Feb | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 4.4 mg/L | Aug | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 25 mg/L | May | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 12 mg/L | Jun | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 7.1 mg/L | Jul | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.6 mg/L | Dec | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.7 mg/L | Mar | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 4.4 mg/L | Sep | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 18 mg/L | Oct | 001 |
| Nitrogen, ammonia total [as N] | 30-day average | ≤ 5.6 mg/L | Nov | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 21 mg/L | Apr | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 23 mg/L | Jan | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 23 mg/L | Feb | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 16 mg/L | Aug | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 25 mg/L | May | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 25 mg/L | Jun | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 25 mg/L | Jul | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 21 mg/L | Dec | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 22 mg/L | Mar | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 17 mg/L | Sep | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 25 mg/L | Oct | 001 |
| Nitrogen, ammonia total [as N] | daily maximum | ≤ 21 mg/L | Nov | 001 |
| Oil and grease | instantaneous maximum | ≤ 10 mg/L | all year | 001 |
| Flow, in conduit or thru treatment plant | 30-day average | ≤ .215 MGD | all year | 001 |
| Flow, in conduit or thru treatment plant | daily maximum | report only (MGD) | all year | 001 |
| Chlorine, total residual | 30-day average | ≤ .011 mg/L | all year | 001 |
| Chlorine, total residual | instantaneous maximum | ≤ .019 mg/L | all year | 001 |
| E. coli | 30-day geometric mean | ≤ 630 #/100mL | all year | 001 |
| E. coli | maximum 7-day geometric mean | ≤ 1260 #/100mL | all year | 001 |
| Solids, total dissolved | 30-day average | report only (mg/L) | all year | 001 |
| Solids, total dissolved | daily maximum | report only (mg/L) | all year | 001 |
| Solids, total dissolved | 30-day average | report only (mg/L) | all year | 001 |
| Solids, total dissolved | daily maximum | report only (mg/L) | 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 |
| Oil and grease visual | instantaneous maximum | report only (abst=0;prst=1) | all year | 001 |
| Plant capacity fact. percent of capacity | 30-day average | report only (%) | all year | 300 |
| Plant capacity fact. percent of capacity | 30-day average | report only (%) | all year | 300 |
| BOD, 5-day, 20 deg. C | 30-day average | report only (mg/L) | all year | 300 |
| BOD, 5-day, 20 deg. C | maximum 7-day average | report only (mg/L) | all year | 300 |
| BOD, 5-day, 20 deg. C | 30-day average | report only (lb/d) | all year | 300 |
| BOD, 5-day, 20 deg. C | maximum 7-day average | report only (lb/d) | all year | 300 |
| Solids, total suspended | 30-day average | report only (mg/L) | all year | 300 |
| Solids, total suspended | maximum 7-day average | report only (mg/L) | all year | 300 |
| Flow, in conduit or thru treatment plant | 30-day average | report only (MGD) | all year | 300 |
| Flow, in conduit or thru treatment plant | daily maximum | report only (MGD) | all year | 300 |
Cited limits by parameter: Colorado'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/CO0020788 · MCP: https://passage-data.com/mcp