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City of Colfax

Sewage treatment plant, Colfax, Iowa. NPDES permit IA0041980, in force until Aug 31, 2030. Last 12 months: over a limit 7 times (last July 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: form A monthly (29 values)
Last report on file
August 2026
Oct 2024 – Sep 2025
6 values over a limit, 0 required values missing, 0 of 12 reports late

Last 12 months (Oct 1, 2025 – Sep 30, 2026)

Period endingParameterReportedLimitOver by
November 2025Solids, total suspended, 30-day average32≤ 30 mg/L7%
November 2025Solids, total suspended, 7-day average79≤ 45 mg/L76%
December 2025pH, daily minimum6.47≥ 6.5 SU—
December 2025pH, daily maximum9.05≤ 9 SU—
March 2026Solids, total suspended, 7-day average61≤ 45 mg/L36%
April 2026Chlorine, total residual, daily maximum.166414≤ .13 lb/d28%
July 2026Chlorine, total residual, daily maximum.143264≤ .13 lb/d10%

Limits in force (73)

ParameterStatisticLimitMonths
BOD, 5-day, 20 deg. C30-day averagereport only (mg/L)all year
BOD, 5-day, 20 deg. Cdaily maximumreport only (mg/L)all year
BOD, 5-day, 20 deg. C30-day averagereport only (lb/d)all year
BOD, 5-day, 20 deg. Cdaily maximumreport only (lb/d)all year
pHdaily minimum≥ 6.5 SUall year
pHdaily maximum≤ 9 SUall year
pH30-day averagereport only (SU)all year
pHdaily maximumreport only (SU)all year
Solids, total suspended30-day average≤ 30 mg/Lall year
Solids, total suspended7-day average≤ 45 mg/Lall year
Solids, total suspended30-day average≤ 171 lb/dall year
Solids, total suspended7-day average≤ 257 lb/dall year
Solids, total suspended30-day averagereport only (mg/L)all year
Solids, total suspendeddaily maximumreport only (mg/L)all year
Solids, total suspended30-day averagereport only (lb/d)all year
Solids, total suspendeddaily maximumreport only (lb/d)all year
Nitrogen, ammonia total [as N]30-day average≤ 19.6 mg/LMay
Nitrogen, ammonia total [as N]30-day average≤ 20.7 mg/LMar
Nitrogen, ammonia total [as N]30-day average≤ 19.1 mg/LNov
Nitrogen, ammonia total [as N]30-day average≤ 22.3 mg/LJan
Nitrogen, ammonia total [as N]30-day average≤ 20.2 mg/LApr
Nitrogen, ammonia total [as N]30-day average≤ 21.2 mg/LDec
Nitrogen, ammonia total [as N]30-day average≤ 20.9 mg/LOct
Nitrogen, ammonia total [as N]30-day average≤ 22.7 mg/LFeb
Nitrogen, ammonia total [as N]30-day average≤ 21.8 mg/LSep
Nitrogen, ammonia total [as N]30-day average≤ 18.8 mg/LJun
Nitrogen, ammonia total [as N]30-day average≤ 22.7 mg/LJul
Nitrogen, ammonia total [as N]30-day average≤ 20.6 mg/LAug
Nitrogen, ammonia total [as N]daily maximum≤ 19.6 mg/LMay
Nitrogen, ammonia total [as N]daily maximum≤ 20.7 mg/LMar
Nitrogen, ammonia total [as N]daily maximum≤ 19.1 mg/LNov
Nitrogen, ammonia total [as N]daily maximum≤ 22.3 mg/LJan
Nitrogen, ammonia total [as N]daily maximum≤ 20.2 mg/LApr
Nitrogen, ammonia total [as N]daily maximum≤ 21.2 mg/LDec
Nitrogen, ammonia total [as N]daily maximum≤ 20.9 mg/LOct
Nitrogen, ammonia total [as N]daily maximum≤ 22.7 mg/LFeb
Nitrogen, ammonia total [as N]daily maximum≤ 21.8 mg/LSep
Nitrogen, ammonia total [as N]daily maximum≤ 18.8 mg/LJun
Nitrogen, ammonia total [as N]daily maximum≤ 22.7 mg/LJul
Nitrogen, ammonia total [as N]daily maximum≤ 20.6 mg/LAug
Nitrogen, ammonia total [as N]30-day average≤ 99.1 lb/dMay
Nitrogen, ammonia total [as N]30-day average≤ 100.3 lb/dMar
Nitrogen, ammonia total [as N]30-day average≤ 96 lb/dNov
Nitrogen, ammonia total [as N]30-day average≤ 106.2 lb/dJan
Nitrogen, ammonia total [as N]30-day average≤ 102.3 lb/dApr
Nitrogen, ammonia total [as N]30-day average≤ 105.7 lb/dDec
Nitrogen, ammonia total [as N]30-day average≤ 104.1 lb/dOct
Nitrogen, ammonia total [as N]30-day average≤ 104 lb/dFeb
Nitrogen, ammonia total [as N]30-day average≤ 76.6 lb/dSep
Nitrogen, ammonia total [as N]30-day average≤ 71.5 lb/dJun
Nitrogen, ammonia total [as N]30-day average≤ 74.8 lb/dJul
Nitrogen, ammonia total [as N]30-day average≤ 80 lb/dAug
Nitrogen, ammonia total [as N]daily maximum≤ 99.1 lb/dMay
Nitrogen, ammonia total [as N]daily maximum≤ 100.3 lb/dMar
Nitrogen, ammonia total [as N]daily maximum≤ 96 lb/dNov
Nitrogen, ammonia total [as N]daily maximum≤ 106.2 lb/dJan
Nitrogen, ammonia total [as N]daily maximum≤ 102.3 lb/dApr
Nitrogen, ammonia total [as N]daily maximum≤ 105.7 lb/dDec
Nitrogen, ammonia total [as N]daily maximum≤ 104.1 lb/dOct
Nitrogen, ammonia total [as N]daily maximum≤ 104 lb/dFeb
Nitrogen, ammonia total [as N]daily maximum≤ 76.6 lb/dSep
Nitrogen, ammonia total [as N]daily maximum≤ 88 lb/dJun
Nitrogen, ammonia total [as N]daily maximum≤ 74.8 lb/dJul
Nitrogen, ammonia total [as N]daily maximum≤ 84.6 lb/dAug
Chlorine, total residual30-day average≤ .028 mg/Lall year
Chlorine, total residualdaily maximum≤ .028 mg/Lall year
Chlorine, total residual30-day average≤ .13 lb/dall year
Chlorine, total residualdaily maximum≤ .13 lb/dall year
E. coligeometric mean≤ 126 #/100mLMar–Nov
BOD, carbonaceous [5 day, 20 C]30-day average≤ 25 mg/Lall year
BOD, carbonaceous [5 day, 20 C]7-day average≤ 40 mg/Lall year
BOD, carbonaceous [5 day, 20 C]30-day average≤ 143 lb/dall year
BOD, carbonaceous [5 day, 20 C]7-day average≤ 229 lb/dall year

How strict are these limits?

Cited limits by parameter: Iowa's rules and the federal ones.

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