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City of Chinook

Sewage treatment plant, Chinook, Montana. NPDES permit MT0020125 expired Dec 31, 2025; its limits still apply. Last 12 months: no values over a limit. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 28 days after each period: form A monthly (30 values), form UP quarterly (5 values), form S1 twice a year
Last report on file
September 2026
Oct 2024 – Sep 2025
0 values over a limit, 0 required values missing, 0 of 18 reports late

Limits in force (38)

ParameterStatisticLimitMonths
Temperature, water deg. centigrademonthly averagereport only (deg C)all year
Temperature, water deg. centigradeweekly maximumreport only (deg C)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. Cmaximum weekly average≤ 45 mg/Lall year
BOD, 5-day, 20 deg. Cmonthly average≤ 125 lb/dall year
BOD, 5-day, 20 deg. Cmaximum weekly average≤ 188 lb/dall year
BOD, 5-day, 20 deg. Cmonthly averagereport only (mg/L)all year
pHdaily minimum≥ 6 SUall year
pHdaily maximum≤ 9 SUall year
pHminimumreport only (SU)all year
pHmaximumreport only (SU)all year
Solids, total suspendedmonthly average≤ 30 mg/Lall year
Solids, total suspendedmaximum weekly average≤ 45 mg/Lall year
Solids, total suspendedmonthly average≤ 125 lb/dall year
Solids, total suspendedmaximum weekly average≤ 188 lb/dall year
Solids, total suspendedmonthly averagereport only (mg/L)all year
Oil & Greasemonthly maximum≤ 10 mg/Lall year
Oil & Greasedaily maximum≤ 10 mg/Lall year
Nitrogen, total [as N]monthly averagereport only (mg/L)Jun–Sep
Nitrogen, total [as N]monthly average≤ 31.1 lb/dJun–Sep
Nitrogen, ammonia total [as N]monthly averagereport only (mg/L)all year
Nitrogen, ammonia total [as N]maximum weekly averagereport only (mg/L)all year
Nitrogen, ammonia total [as N]monthly averagereport only (mg/L)all year
Nitrogen, ammonia total [as N]daily maximumreport only (mg/L)all year
Nitrogen, Kjeldahl, total [as N]monthly averagereport only (mg/L)Jun–Sep
Nitrite + Nitrate total [as N]monthly averagereport only (mg/L)all year
Nitrite + Nitrate total [as N]monthly averagereport only (mg/L)all year
Phosphorus, total [as P]monthly averagereport only (mg/L)Jun–Sep
Phosphorus, total [as P]monthly average≤ 5.7 lb/dJun–Sep
E. coli, MTEC-MFmonthly geometric mean≤ 126 #/100mLApr–Oct
E. coli, MTEC-MFmonthly geometric mean≤ 630 #/100mLJan, Feb, Mar, Nov, Dec
E. coli, MTEC-MFmaximum weekly average≤ 252 #/100mLApr–Oct
E. coli, MTEC-MFmaximum weekly average≤ 1260 #/100mLJan, Feb, Mar, Nov, Dec
BOD, 5-day, percent removalminimum≥ 85 %all year
Solids, suspended percent removalminimum≥ 85 %all year
Oil and grease visualvaluereport only (Y=0;N=1)all year

How strict are these limits?

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

Check this month's numbers Email me before each report is due

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On EPA ECHO: Facility report · DMR history

Your permit document is the final word. As JSON: /api/v1/permits/MT0020125 · MCP: https://passage-data.com/mcp