CITY OF GREAT FALLS — NPDES permit MT0021920: limits, due date and EPA's record

NPDES permit MT0021920 · Major POTW · administratively continued, expires 2024-08-31 · EPA's file as of 2026-09-19

This permit expired on 2024-08-31 and is administratively continued: its last limits keep applying until a new permit is issued, and EPA still expects the reports.

EPA's record, 2025-09-01 to 2026-08-31

Reporting

Reports are due about 28 days after each monitoring period ends (the most common figure among MT permits in EPA's filings — check your permit).

Limits in force (42)

Outfall	Parameter	Statistic	Limit	Months
003	Temperature, water deg. centigrade	MO AVG	report only	all year
003	Temperature, water deg. centigrade	DAILY MX	report only	all year
003	Flow rate	DAILY AV	report only	all year
003	Flow rate	DAILY MX	report only	all year
003	Flow rate	DAILY AV	report only	all year
003	Flow rate	DAILY MX	report only	all year
003	Oxygen, dissolved [DO]	SINGSAMP	report only	all year
003	BOD, 5-day, 20 deg. C	MO AVG	<= 25 mg/L	all year
003	BOD, 5-day, 20 deg. C	7 DA AVG	<= 40 mg/L	all year
003	BOD, 5-day, 20 deg. C	MO AVG	<= 2773 lb/d	all year
003	BOD, 5-day, 20 deg. C	7 DA AVG	<= 4437 lb/d	all year
003	BOD, 5-day, 20 deg. C	MO AVG	report only	all year
003	pH	INST MIN	report only	all year
003	pH	INST MAX	report only	all year
003	Solids, total suspended	MO AVG	<= 30 mg/L	all year
003	Solids, total suspended	7 DA AVG	<= 45 mg/L	all year
003	Solids, total suspended	MO AVG	<= 3328 lb/d	all year
003	Solids, total suspended	7 DA AVG	<= 4991 lb/d	all year
003	Solids, total suspended	MO AVG	report only	all year
003	Oil and grease, hexane extr method	INST MAX	<= 10 mg/L	all year
003	Nitrogen, total [as N]	MO AVG	report only	Jul, Aug, Sep
003	Nitrogen, total [as N]	MO AVG	report only	Jul, Aug, Sep
003	Nitrogen, ammonia total [as N]	MO AVG	report only	all year
003	Nitrogen, Kjeldahl, total [as N]	MO AVG	report only	Jul, Aug, Sep
003	Nitrite + Nitrate total [as N]	MO AVG	report only	all year
003	Nitrite + Nitrate total [as N]	DAILY MX	report only	all year
003	Phosphorus, total [as P]	MO AVG	report only	Jul, Aug, Sep
003	Phosphorus, total [as P]	MO AVG	report only	Jul, Aug, Sep
003	Arsenic, total recoverable	MO AVG	<= 19.8 ug/L	all year
003	Arsenic, total recoverable	DAILY MX	<= 19.8 ug/L	all year
003	Lead, total recoverable	MO AVG	report only	all year
003	E. coli, MTEC-MF	30DA GEO	<= 126 CFU/100mL	Apr, May, Jun, Jul, Aug, Sep, Oct
003	E. coli, MTEC-MF	30DA GEO	<= 630 CFU/100mL	Jan, Feb, Mar, Nov, Dec
003	E. coli, MTEC-MF	7 DA GEO	<= 252 CFU/100mL	Apr, May, Jun, Jul, Aug, Sep, Oct
003	E. coli, MTEC-MF	7 DA GEO	<= 1260 CFU/100mL	Jan, Feb, Mar, Nov, Dec
003	Cyanide, total recoverable	MO AVG	<= 19.9 ug/L	all year
003	Cyanide, total recoverable	DAILY MX	<= 19.9 ug/L	all year
003	BOD, 5-day, percent removal	MINIMUM	>= 85 %	all year
003	Solids, suspended percent removal	MINIMUM	>= 85 %	all year
003	Oil and grease visual	VALUE	report only	all year
003	Pass/Fail Static Renewal 48Hr Acute Ceriodaphnia dubia	VALUE	report only	all year
003	Pass/Fail Static Renewal 96Hr Acute Pimephales Promelas	VALUE	report only	all year