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City of Oskaloosa

Sewage treatment plant, major discharger, Oskaloosa, Iowa. NPDES permit IA0038539 expired Mar 31, 2026; its limits still apply. Last 12 months: over a limit 25 times (last August 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: form A monthly (51 values)
Last report on file
August 2026
Oct 2024 – Sep 2025
16 values over a limit, 0 required values missing, 1 of 12 reports late

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

All 25 values over a limit
Period endingParameterReportedLimitOver by
October 2025Copper, total [as Cu], 30-day average.017≤ .01687 mg/L1%
October 2025Copper, total [as Cu], daily maximum.027≤ .0269 mg/L0%
October 2025Nitrogen, ammonia total [as N], 30-day average4.981111≤ 1.6 mg/L211%
October 2025Nitrogen, ammonia total [as N], daily maximum19.2≤ 11.1 mg/L73%
October 2025Oxygen, dissolved [DO], daily minimum2.35≥ 5 mg/L53%
November 2025Copper, total [as Cu], 30-day average.02525≤ .01687 mg/L50%
November 2025Copper, total [as Cu], daily maximum.059≤ .0269 mg/L119%
November 2025Nitrogen, ammonia total [as N], 30-day average2.71≤ 2.3 mg/L18%
December 2025Copper, total [as Cu], daily maximum.028≤ .0269 mg/L4%
December 2025Nitrogen, ammonia total [as N], 30-day average3.9955≤ 2.5 mg/L60%
December 2025Oxygen, dissolved [DO], daily minimum3.93≥ 5 mg/L21%
January 2026Copper, total [as Cu], daily maximum.038≤ .0269 mg/L41%
February 2026Copper, total [as Cu], 30-day average111.6762≤ .3517 lb/d31653%
February 2026Copper, total [as Cu], 30-day average19.68812≤ .01687 mg/L—
February 2026Copper, total [as Cu], daily maximum290.2194≤ .5608 lb/d51651%
February 2026Copper, total [as Cu], daily maximum49.5≤ .0269 mg/L—
March 2026Copper, total [as Cu], 30-day average.01736≤ .01687 mg/L3%
March 2026Copper, total [as Cu], daily maximum.032≤ .0269 mg/L19%
July 2026Copper, total [as Cu], 30-day average.01745≤ .01687 mg/L3%
July 2026Nitrogen, ammonia total [as N], 30-day average2.095≤ 1 mg/L110%
July 2026Oxygen, dissolved [DO], daily minimum2.8≥ 5 mg/L44%
July 2026Solids, total suspended, 7-day average55≤ 45 mg/L22%
August 2026Nitrogen, ammonia total [as N], 30-day average2.8325≤ 1 mg/L183%
August 2026Nitrogen, ammonia total [as N], daily maximum7.84≤ 5 mg/L57%
August 2026Oxygen, dissolved [DO], daily minimum3.27≥ 5 mg/L35%

Limits in force (95)

ParameterStatisticLimitMonths
Oxygen, dissolved [DO]daily minimum≥ 5 mg/Lall year
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≤ 416 lb/dall year
Solids, total suspended7-day average≤ 623 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, total [as N]30-day averagereport only (mg/L)all year
Nitrogen, total [as N]daily maximumreport only (mg/L)all year
Nitrogen, total [as N]30-day averagereport only (lb/d)all year
Nitrogen, total [as N]daily maximumreport only (lb/d)all year
Nitrogen, total [as N]30-day averagereport only (mg/L)all year
Nitrogen, total [as N]daily maximumreport only (mg/L)all year
Nitrogen, total [as N]30-day averagereport only (lb/d)all year
Nitrogen, total [as N]daily maximumreport only (lb/d)all year
Nitrogen, ammonia total [as N]30-day average≤ 3.4 mg/LMar
Nitrogen, ammonia total [as N]30-day average≤ 3.4 mg/LJan
Nitrogen, ammonia total [as N]30-day average≤ 1.3 mg/LJun
Nitrogen, ammonia total [as N]30-day average≤ 2.5 mg/LDec
Nitrogen, ammonia total [as N]30-day average≤ 1.7 mg/LMay
Nitrogen, ammonia total [as N]30-day average≤ 1.6 mg/LOct
Nitrogen, ammonia total [as N]30-day average≤ 1.5 mg/LApr
Nitrogen, ammonia total [as N]30-day average≤ 4 mg/LFeb
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LAug
Nitrogen, ammonia total [as N]30-day average≤ 1 mg/LJul
Nitrogen, ammonia total [as N]30-day average≤ 2.3 mg/LNov
Nitrogen, ammonia total [as N]30-day average≤ 1.1 mg/LSep
Nitrogen, ammonia total [as N]daily maximum≤ 14.7 mg/LMar
Nitrogen, ammonia total [as N]daily maximum≤ 15.2 mg/LJan
Nitrogen, ammonia total [as N]daily maximum≤ 6.6 mg/LJun
Nitrogen, ammonia total [as N]daily maximum≤ 16 mg/LDec
Nitrogen, ammonia total [as N]daily maximum≤ 11.1 mg/LMay
Nitrogen, ammonia total [as N]daily maximum≤ 11.1 mg/LOct
Nitrogen, ammonia total [as N]daily maximum≤ 15.7 mg/LApr
Nitrogen, ammonia total [as N]daily maximum≤ 14.2 mg/LFeb
Nitrogen, ammonia total [as N]daily maximum≤ 5 mg/LAug
Nitrogen, ammonia total [as N]daily maximum≤ 4.5 mg/LJul
Nitrogen, ammonia total [as N]daily maximum≤ 14.7 mg/LNov
Nitrogen, ammonia total [as N]daily maximum≤ 6.1 mg/LSep
Nitrogen, ammonia total [as N]30-day average≤ 71 lb/dMar
Nitrogen, ammonia total [as N]30-day average≤ 71 lb/dJan
Nitrogen, ammonia total [as N]30-day average≤ 27.3 lb/dJun
Nitrogen, ammonia total [as N]30-day average≤ 51.6 lb/dDec
Nitrogen, ammonia total [as N]30-day average≤ 36.2 lb/dMay
Nitrogen, ammonia total [as N]30-day average≤ 32.4 lb/dOct
Nitrogen, ammonia total [as N]30-day average≤ 31.8 lb/dApr
Nitrogen, ammonia total [as N]30-day average≤ 82.4 lb/dFeb
Nitrogen, ammonia total [as N]30-day average≤ 19.9 lb/dAug
Nitrogen, ammonia total [as N]30-day average≤ 21 lb/dJul
Nitrogen, ammonia total [as N]30-day average≤ 48.4 lb/dNov
Nitrogen, ammonia total [as N]30-day average≤ 22 lb/dSep
Nitrogen, ammonia total [as N]daily maximum≤ 306.2 lb/dMar
Nitrogen, ammonia total [as N]daily maximum≤ 316.7 lb/dJan
Nitrogen, ammonia total [as N]daily maximum≤ 131.4 lb/dJun
Nitrogen, ammonia total [as N]daily maximum≤ 332.8 lb/dDec
Nitrogen, ammonia total [as N]daily maximum≤ 223.1 lb/dMay
Nitrogen, ammonia total [as N]daily maximum≤ 166.8 lb/dOct
Nitrogen, ammonia total [as N]daily maximum≤ 327.4 lb/dApr
Nitrogen, ammonia total [as N]daily maximum≤ 296 lb/dFeb
Nitrogen, ammonia total [as N]daily maximum≤ 100.1 lb/dAug
Nitrogen, ammonia total [as N]daily maximum≤ 87.6 lb/dJul
Nitrogen, ammonia total [as N]daily maximum≤ 306.2 lb/dNov
Nitrogen, ammonia total [as N]daily maximum≤ 120.9 lb/dSep
Nitrogen, Kjeldahl, total [as N]30-day averagereport only (mg/L)all year
Nitrogen, Kjeldahl, total [as N]daily maximumreport only (mg/L)all year
Nitrogen, Kjeldahl, total [as N]30-day averagereport only (lb/d)all year
Nitrogen, Kjeldahl, total [as N]daily maximumreport only (lb/d)all year
Phosphorus, total [as P]30-day averagereport only (mg/L)all year
Phosphorus, total [as P]daily maximumreport only (mg/L)all year
Phosphorus, total [as P]30-day averagereport only (lb/d)all year
Phosphorus, total [as P]daily maximumreport only (lb/d)all year
Phosphorus, total [as P]30-day averagereport only (mg/L)all year
Phosphorus, total [as P]daily maximumreport only (mg/L)all year
Phosphorus, total [as P]30-day averagereport only (lb/d)all year
Phosphorus, total [as P]daily maximumreport only (lb/d)all year
Copper, total [as Cu]30-day average≤ .01687 mg/Lall year
Copper, total [as Cu]daily maximum≤ .0269 mg/Lall year
Copper, total [as Cu]30-day average≤ .3517 lb/dall year
Copper, total [as Cu]daily maximum≤ .5608 lb/dall year
Toxicity [acute], Ceriodaphnia dubiadaily maximum≤ 1 N=0;Y=1all year
Toxicity [acute], Pimephales promelas [Fathead Minnow]daily maximum≤ 1 N=0;Y=1all year
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≤ 346 lb/dall year
BOD, carbonaceous [5 day, 20 C]7-day average≤ 554 lb/dall year

How strict are these limits?

Cited limits by parameter: Iowa'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/IA0038539 · MCP: https://passage-data.com/mcp