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City of Helena

Sewage treatment plant, major discharger, Helena, Montana. NPDES permit MT0022641 expired Sep 30, 2017; its limits still apply. Last 12 months: over a limit 4 times (last February 2026). Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (44 values), form Q quarterly (12 values), form W quarterly (2 values), form Y yearly, form YR yearly
Last report on file
August 2026
Oct 2024 – Sep 2025
17 values over a limit, 0 required values missing, 1 of 22 reports late

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

Period endingParameterReportedLimitOver by
December 2025Zinc, total recoverable, daily maximum.77 mg/L≤ .11 mg/L600%
December 2025Zinc, total recoverable, monthly average.412 mg/L≤ .11 mg/L275%
February 2026Zinc, total recoverable, daily maximum.122 mg/L≤ .11 mg/L11%
February 2026Zinc, total recoverable, monthly average.122 mg/L≤ .11 mg/L11%

Limits in force (79)

ParameterStatisticLimitMonths
Temperature, water deg. centigrademonthly averagereport only (deg C)all year
Temperature, water deg. centigradedaily maximumreport only (deg C)all year
Flow ratemonthly averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
Flow ratemonthly averagereport only (MGD)all year
Flow ratedaily maximumreport only (MGD)all year
BOD, 5-day, 20 deg. Cmonthly average≤ 30 mg/Lall year
BOD, 5-day, 20 deg. Cweekly average≤ 45 mg/Lall year
BOD, 5-day, 20 deg. Cmonthly average≤ 1351 lb/dall year
BOD, 5-day, 20 deg. Cweekly average≤ 2027 lb/dall year
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all year
BOD, 5-day, 20 deg. Cweekly averagereport only (mg/L)all year
pHinstantaneous minimum≥ 6.5 SUall year
pHinstantaneous maximum≤ 9 SUall year
Solids, total suspendedmonthly average≤ 30 mg/Lall year
Solids, total suspendedweekly average≤ 45 mg/Lall year
Solids, total suspendedmonthly average≤ 1351 lb/dall year
Solids, total suspendedweekly average≤ 2027 lb/dall year
Solids, total suspendedmonthly averagereport only (mg/L)all year
Solids, total suspendedweekly averagereport only (mg/L)all year
Oil and grease, hexane extr methoddaily maximum≤ 10 mg/Lall year
Nitrogen, total [as N]annual averagereport only (ton/yr)all year
Nitrogen, total [as N]monthly averagereport only (mg/L)all year
Nitrogen, total [as N]weekly averagereport only (mg/L)all year
Nitrogen, total [as N]monthly average≤ 241 lb/dall year
Nitrogen, total [as N]weekly average≤ 308 lb/dall year
Nitrogen, ammonia total [as N]monthly average≤ 1.67 mg/Lall year
Nitrogen, ammonia total [as N]weekly average≤ 3.83 mg/Lall year
Nitrogen, Kjeldahl, total [as N]monthly averagereport only (mg/L)all year
Nitrogen, Kjeldahl, total [as N]weekly averagereport only (mg/L)all year
Nitrite + Nitrate total [as N]monthly averagereport only (mL/L)all year
Nitrite + Nitrate total [as N]weekly averagereport only (mL/L)all year
Phosphorus, total [as P]monthly averagereport only (mg/L)all year
Phosphorus, total [as P]weekly averagereport only (mg/L)all year
Phosphorus, total [as P]monthly average≤ 108 lb/dall year
Phosphorus, total [as P]annual averagereport only (ton/yr)all year
Phosphorus, total [as P]weekly average≤ 166 lb/dall year
Cyanide, total [as CN]valuereport only (mg/L)all year
Hardness, total [as CaCO3]valuereport only (mg/L)all year
Arsenic, total recoverablevaluereport only (mg/L)all year
Arsenic, total recoverablevaluereport only (mg/L)all year
Selenium, total recoverablevaluereport only (mg/L)all year
Selenium, total recoverablevaluereport only (mg/L)all year
Thallium, total recoverablevaluereport only (mg/L)all year
Thallium, total recoverablevaluereport only (mg/L)all year
Beryllium, total recoverable [as Be]valuereport only (mg/L)all year
Beryllium, total recoverable [as Be]valuereport only (mg/L)all year
Nickel, total recoverablevaluereport only (mg/L)all year
Nickel, total recoverablevaluereport only (mg/L)all year
Silver total recoverablevaluereport only (mg/L)all year
Silver total recoverablevaluereport only (mg/L)all year
Zinc, total recoverablemonthly average≤ .11 mg/Lall year
Zinc, total recoverabledaily maximum≤ .11 mg/Lall year
Aluminum, dissolved [as Al]valuereport only (mg/L)all year
Aluminum, dissolved [as Al]valuereport only (mg/L)all year
Cadmium, total recoverablevaluereport only (mg/L)all year
Cadmium, total recoverablevaluereport only (mg/L)all year
Lead, total recoverablevaluereport only (mg/L)all year
Lead, total recoverablevaluereport only (mg/L)all year
Chromium, total recoverablevaluereport only (mg/L)all year
Copper, total recoverablemonthly average≤ .009 mg/Lall year
Copper, total recoverablevaluereport only (mg/L)all year
Copper, total recoverabledaily maximum≤ .013 mg/Lall year
Antimony, total recoverablevaluereport only (mg/L)all year
Antimony, total recoverablevaluereport only (mg/L)all year
E. coli, MTEC-MFmonthly geometric mean≤ 126 CFU/100mLApr–Oct
E. coli, MTEC-MFmonthly geometric mean≤ 630 CFU/100mLJan, Feb, Mar, Nov, Dec
E. coli, MTEC-MFweekly average≤ 252 CFU/100mLApr–Oct
E. coli, MTEC-MFweekly average≤ 1260 CFU/100mLJan, Feb, Mar, Nov, Dec
Phenolsvaluereport only (mg/L)all year
Solids, total dissolved [TDS]valuereport only (mg/L)all year
Mercury, total recoverablevaluereport only (mg/L)all year
Mercury, total recoverablevaluereport only (mg/L)all year
BOD, 5-day, percent removalminimum≥ 85 %all year
Solids, suspended percent removalminimum≥ 85 %all year
Oil and grease visualvaluereport only (N=0;Y=1)all year
Report due [yrmoda]valuereport only (N=0;Y=1)all year
Pass/Fail Static Renewal 7 Day Chronic Ceriodaphnia dubiasingle samplereport only (pass=0;fail=1)all year
Pass/Fail Static Renewal 7Day Chronic Pimephales promelassingle samplereport only (pass=0;fail=1)all year

How strict are these limits?

Cited limits by parameter: Montana'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/MT0022641 · MCP: https://passage-data.com/mcp