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City of Larchwood

Sewage treatment plant, Larchwood, Iowa. NPDES permit IA0047333, in force until Sep 30, 2029. Last 12 months: over a limit 2 times (last November 2025), 1 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 15 days after each period: form A monthly (14 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
2 values over a limit, 0 required values missing, 1 of 12 reports late

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

Period endingParameterReportedLimitOver by
November 2025Chloride [as Cl], 30-day average394≤ 389 mg/L1%
November 2025pH, daily maximum9.33≤ 9 SU—

Limits in force (58)

ParameterStatisticLimitMonths
pHdaily minimum≥ 6 SUall year
pHdaily maximum≤ 9 SUall year
Solids, total suspended30-day average≤ 80 mg/Lall year
Solids, total suspended7-day average≤ 120 mg/Lall year
Nitrogen, ammonia total [as N]30-day average≤ 2.4 mg/LApr
Nitrogen, ammonia total [as N]30-day average≤ 1.4 mg/LJul
Nitrogen, ammonia total [as N]30-day average≤ 3.2 mg/LOct
Nitrogen, ammonia total [as N]30-day average≤ 4.2 mg/LDec
Nitrogen, ammonia total [as N]30-day average≤ 1.7 mg/LJun
Nitrogen, ammonia total [as N]30-day average≤ 5.4 mg/LJan
Nitrogen, ammonia total [as N]30-day average≤ 1.8 mg/LSep
Nitrogen, ammonia total [as N]30-day average≤ 1.3 mg/LAug
Nitrogen, ammonia total [as N]30-day average≤ 3.8 mg/LNov
Nitrogen, ammonia total [as N]30-day average≤ 2.2 mg/LMay
Nitrogen, ammonia total [as N]30-day average≤ 6.2 mg/LFeb
Nitrogen, ammonia total [as N]30-day average≤ 4.9 mg/LMar
Nitrogen, ammonia total [as N]daily maximum≤ 7.8 mg/LApr
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LJul
Nitrogen, ammonia total [as N]daily maximum≤ 6.9 mg/LOct
Nitrogen, ammonia total [as N]daily maximum≤ 9 mg/LDec
Nitrogen, ammonia total [as N]daily maximum≤ 8.3 mg/LJun
Nitrogen, ammonia total [as N]daily maximum≤ 12.8 mg/LJan
Nitrogen, ammonia total [as N]daily maximum≤ 6.9 mg/LSep
Nitrogen, ammonia total [as N]daily maximum≤ 6.9 mg/LAug
Nitrogen, ammonia total [as N]daily maximum≤ 6.9 mg/LNov
Nitrogen, ammonia total [as N]daily maximum≤ 8.2 mg/LMay
Nitrogen, ammonia total [as N]daily maximum≤ 15.5 mg/LFeb
Nitrogen, ammonia total [as N]daily maximum≤ 10.1 mg/LMar
Nitrogen, ammonia total [as N]30-day average≤ 26.6 lb/dApr
Nitrogen, ammonia total [as N]30-day average≤ 16 lb/dJul
Nitrogen, ammonia total [as N]30-day average≤ 36.3 lb/dOct
Nitrogen, ammonia total [as N]30-day average≤ 47.8 lb/dDec
Nitrogen, ammonia total [as N]30-day average≤ 19 lb/dJun
Nitrogen, ammonia total [as N]30-day average≤ 61.3 lb/dJan
Nitrogen, ammonia total [as N]30-day average≤ 20.7 lb/dSep
Nitrogen, ammonia total [as N]30-day average≤ 14.6 lb/dAug
Nitrogen, ammonia total [as N]30-day average≤ 42.3 lb/dNov
Nitrogen, ammonia total [as N]30-day average≤ 24.3 lb/dMay
Nitrogen, ammonia total [as N]30-day average≤ 70.2 lb/dFeb
Nitrogen, ammonia total [as N]30-day average≤ 55 lb/dMar
Nitrogen, ammonia total [as N]daily maximum≤ 88 lb/dApr
Nitrogen, ammonia total [as N]daily maximum≤ 93.4 lb/dJul
Nitrogen, ammonia total [as N]daily maximum≤ 77.3 lb/dOct
Nitrogen, ammonia total [as N]daily maximum≤ 101.7 lb/dDec
Nitrogen, ammonia total [as N]daily maximum≤ 93.4 lb/dJun
Nitrogen, ammonia total [as N]daily maximum≤ 144.1 lb/dJan
Nitrogen, ammonia total [as N]daily maximum≤ 77.3 lb/dSep
Nitrogen, ammonia total [as N]daily maximum≤ 77.3 lb/dAug
Nitrogen, ammonia total [as N]daily maximum≤ 77.3 lb/dNov
Nitrogen, ammonia total [as N]daily maximum≤ 92.2 lb/dMay
Nitrogen, ammonia total [as N]daily maximum≤ 174.4 lb/dFeb
Nitrogen, ammonia total [as N]daily maximum≤ 113.3 lb/dMar
Chloride [as Cl]30-day average≤ 389 mg/Lall year
Chloride [as Cl]daily maximum≤ 629 mg/Lall year
Chloride [as Cl]30-day average≤ 4376 lb/dall year
Chloride [as Cl]daily maximum≤ 7080 lb/dall 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

New limits from Sep 1, 2029

ParameterNew limitNew or tighterMedian, last 12 months× new limit
Nitrogen, ammonia total [as N], 30-day average13.5 lb/d (Sep)tighter——
Nitrogen, ammonia total [as N], 30-day average1.2 mg/L (Sep)tighter——
Nitrogen, ammonia total [as N], 30-day average47.8 lb/d (Feb)tighter——
Nitrogen, ammonia total [as N], 30-day average1.7 mg/L (Oct)tighter——
Nitrogen, ammonia total [as N], 30-day average1.5 mg/L (Jun)tighter——
Nitrogen, ammonia total [as N], 30-day average16.8 lb/d (Jun)tighter——
Nitrogen, ammonia total [as N], 30-day average41.2 lb/d (Mar)tighter——
Nitrogen, ammonia total [as N], 30-day average3.6 mg/L (Jan)tighter——
Nitrogen, ammonia total [as N], 30-day average41 lb/d (Jan)tighter——
Nitrogen, ammonia total [as N], 30-day average19.3 lb/d (Oct)tighter——
Nitrogen, ammonia total [as N], 30-day average2.5 mg/L (Nov)tighter——
Nitrogen, ammonia total [as N], 30-day average28.4 lb/d (Nov)tighter——
Nitrogen, ammonia total [as N], 30-day average2.7 mg/L (Dec)tighter——
Nitrogen, ammonia total [as N], 30-day average30 lb/d (Dec)tighter——
Nitrogen, ammonia total [as N], 30-day average3.7 mg/L (Mar)tighter——
Nitrogen, ammonia total [as N], 30-day average4.2 mg/L (Feb)tighter——
Nitrogen, ammonia total [as N], 30-day average12.5 lb/d (Aug)tighter——
Nitrogen, ammonia total [as N], 30-day average1.1 mg/L (Aug)tighter——
Nitrogen, ammonia total [as N], 30-day average1.9 mg/L (May)tighter——
Nitrogen, ammonia total [as N], 30-day average21.8 lb/d (May)tighter——
Nitrogen, ammonia total [as N], 30-day average1.2 mg/L (Jul)tighter——
Nitrogen, ammonia total [as N], 30-day average13.1 lb/d (Jul)tighter——
Nitrogen, ammonia total [as N], 30-day average1.7 mg/L (Apr)tighter——
Nitrogen, ammonia total [as N], 30-day average18.8 lb/d (Apr)tighter——
Nitrogen, ammonia total [as N], daily maximum35.2 lb/d (Sep)tighter——
Nitrogen, ammonia total [as N], daily maximum3.1 mg/L (Sep)tighter——
Nitrogen, ammonia total [as N], daily maximum42.7 lb/d (Jun)tighter——
Nitrogen, ammonia total [as N], daily maximum33.7 lb/d (Nov)tighter——
Nitrogen, ammonia total [as N], daily maximum9 mg/L (Feb)tighter——
Nitrogen, ammonia total [as N], daily maximum34.2 lb/d (Oct)tighter——
Nitrogen, ammonia total [as N], daily maximum47.5 lb/d (Dec)tighter——
Nitrogen, ammonia total [as N], daily maximum4.2 mg/L (Dec)tighter——
Nitrogen, ammonia total [as N], daily maximum101.8 lb/d (Feb)tighter——
Nitrogen, ammonia total [as N], daily maximum48.8 lb/d (Mar)tighter——
Nitrogen, ammonia total [as N], daily maximum3.8 mg/L (Jun)tighter——
Nitrogen, ammonia total [as N], daily maximum3 mg/L (Oct)tighter——
Nitrogen, ammonia total [as N], daily maximum3 mg/L (Nov)tighter——
Nitrogen, ammonia total [as N], daily maximum4.3 mg/L (Mar)tighter——
Nitrogen, ammonia total [as N], daily maximum3.3 mg/L (Aug)tighter——
Nitrogen, ammonia total [as N], daily maximum36.6 lb/d (Aug)tighter——
Nitrogen, ammonia total [as N], daily maximum3.7 mg/L (May)tighter——
Nitrogen, ammonia total [as N], daily maximum41.7 lb/d (May)tighter——
Nitrogen, ammonia total [as N], daily maximum43.5 lb/d (Jul)tighter——
Nitrogen, ammonia total [as N], daily maximum3.9 mg/L (Jul)tighter——
Nitrogen, ammonia total [as N], daily maximum5.2 mg/L (Apr)tighter——
Nitrogen, ammonia total [as N], daily maximum58.1 lb/d (Apr)tighter——

How strict are these limits?

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

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