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City of Missoula

Sewage treatment plant, major discharger, Missoula, Montana. NPDES permit MT0022594 expired Apr 30, 2020; its limits still apply. Last 12 months: over a limit 7 times (last September 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (50 values), form UP quarterly (1 value), form W quarterly (2 values)
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 0 of 20 reports late

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

Period endingParameterReportedLimitOver by
April 2026BOD, carbonaceous [5 day, 20 C], 30-day average> 269 lb/d≤ 1874 lb/d—
April 2026BOD, carbonaceous [5 day, 20 C], 30-day average> 4.14 mg/L≤ 19 mg/L—
April 2026BOD, carbonaceous [5 day, 20 C], maximum 7-day average> 369 lb/d≤ 2999 lb/d—
April 2026BOD, carbonaceous [5 day, 20 C], maximum 7-day average> 5.39 mg/L≤ 30 mg/L—
April 2026BOD, carbonaceous, percent removal, minimum< 98.4 %≥ 85 %—
June 2026Phosphorus, total [as P], 30-day average102 lb/d≤ 101 lb/d1%
September 2026Nitrogen, total [as N], 30-day average951 lb/d≤ 910 lb/d5%

Limits in force (63)

ParameterStatisticLimitMonths
Temperature, water deg. centigrademinimumreport only (deg C)all year
Temperature, water deg. centigrade30-day averagereport only (deg C)all year
Temperature, water deg. centigrademaximumreport only (deg C)all year
Flow rate30-day averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
Flow rate30-day averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
Oxygen, dissolved [DO]minimumreport only (mg/L)all year
Oxygen, dissolved [DO]30-day averagereport only (mg/L)all year
Oxygen, dissolved [DO]maximumreport only (mg/L)all year
pHdaily minimum≥ 6 SUall year
pHdaily maximum≤ 9 SUall year
Solids, total suspended30-day average≤ 23 mg/Lall year
Solids, total suspendedmaximum 7-day average≤ 34 mg/Lall year
Solids, total suspended30-day average≤ 2249 lb/dall year
Solids, total suspendedmaximum 7-day average≤ 3374 lb/dall year
Solids, total suspended30-day averagereport only (mg/L)all year
Solids, total suspendedmaximum 7-day averagereport only (mg/L)all year
Oil and grease, hexane extr methoddaily maximum≤ 10 mg/Lall year
Nitrogen, total [as N]30-day averagereport only (mg/L)Jun–Sep
Nitrogen, total [as N]30-day averagereport only (mg/L)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Nitrogen, total [as N]maximum 7-day averagereport only (mg/L)Jun–Sep
Nitrogen, total [as N]maximum 7-day averagereport only (mg/L)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Nitrogen, total [as N]30-day average≤ 910 lb/dJun–Sep
Nitrogen, total [as N]30-day averagereport only (lb/d)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Nitrogen, total [as N]maximum 7-day averagereport only (lb/d)Jun–Sep
Nitrogen, total [as N]maximum 7-day averagereport only (lb/d)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Nitrogen, ammonia total [as N]30-day average≤ 3.4 mg/Lall year
Nitrogen, ammonia total [as N]maximum 7-day average≤ 6.9 mg/Lall year
Nitrogen, Kjeldahl, total [as N]30-day averagereport only (mg/L)all year
Nitrite + Nitrate total [as N]30-day averagereport only (mg/L)all year
Phosphorus, total [as P]30-day averagereport only (mg/L)Jun–Sep
Phosphorus, total [as P]30-day averagereport only (mg/L)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Phosphorus, total [as P]maximum 7-day averagereport only (mg/L)Jun–Sep
Phosphorus, total [as P]maximum 7-day averagereport only (mg/L)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Phosphorus, total [as P]30-day average≤ 101 lb/dJun–Sep
Phosphorus, total [as P]30-day averagereport only (lb/d)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Phosphorus, total [as P]daily maximumreport only (lb/d)Jun–Sep
Phosphorus, total [as P]daily maximumreport only (lb/d)Jan, Feb, Mar, Apr, May, Oct, Nov, Dec
Cyanide, total [as CN]daily maximumreport only (ug/L)all year
Iron, total recoverablemonthly average≤ 950 ug/Lall year
Iron, total recoverabledaily maximum≤ 1640 ug/Lall year
Lead, total recoverablemonthly average≤ 2.6 ug/Lall year
Lead, total recoverabledaily maximum≤ 2.9 ug/Lall year
Copper, total recoverablemonthly average≤ 11 ug/Lall year
Copper, total recoverabledaily maximum≤ 13.6 ug/Lall year
E. coli, MTEC-MF30-day geometric mean≤ 630 CFU/100mLJan, Feb, Mar, Nov, Dec
E. coli, MTEC-MF30-day geometric mean≤ 126 CFU/100mLApr–Oct
E. coli, MTEC-MF7-day geometric mean≤ 1260 CFU/100mLJan, Feb, Mar, Nov, Dec
E. coli, MTEC-MF7-day geometric mean≤ 252 CFU/100mLApr–Oct
Chlorine, total residual30-day average≤ .011 mg/Lall year
Chlorine, total residualdaily maximum≤ .019 mg/Lall year
BOD, carbonaceous [5 day, 20 C]30-day average≤ 19 mg/Lall year
BOD, carbonaceous [5 day, 20 C]maximum 7-day average≤ 30 mg/Lall year
BOD, carbonaceous [5 day, 20 C]30-day average≤ 1874 lb/dall year
BOD, carbonaceous [5 day, 20 C]maximum 7-day average≤ 2999 lb/dall year
BOD, carbonaceous [5 day, 20 C]30-day averagereport only (mg/L)all year
BOD, carbonaceous [5 day, 20 C]maximum 7-day averagereport only (mg/L)all year
BOD, carbonaceous, percent removalminimum≥ 85 %all year
Solids, suspended percent removalminimum≥ 85 %all year
Oil and grease visualsingle samplereport only (N=0;Y=1)all year
Pass/Fail Static 48Hr Acute Ceriodaphnia dubiavalue≤ 0 pass=0;fail=1all year
Pass/Fail Static 96 Hr Acute Pimephales Promelasvalue≤ 0 pass=0;fail=1all year

How strict are these limits?

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

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Your permit document is the final word. As JSON: /api/v1/permits/MT0022594 · MCP: https://passage-data.com/mcp