Clean Water Act discharge permit · NPDES IL0025291

MASCOUTAH STP, CITY OF, Mascoutah, IL: NPDES IL0025291 discharge permit, effluent exceedances, inspections, penalties

Administratively continuedPermit status
MinorDischarger class
34Pollutants under a numeric limit
1Pollutants with an effluent exceedance

MASCOUTAH STP, CITY OF, held by MASCOUTAH, CITY OF, holds NPDES permit IL0025291, which discharges to Silver Creek. EPA’s file records it issued February 19, 2020 and expiring February 28, 2025. The status and dates are as EPA’s permit file stood when Velarion loaded it (October 14, 2026); EPA’s free Detailed Facility Report on ECHO carries the permit’s current standing.

Identity

Facility as filed	MASCOUTAH STP, CITY OF
Permittee as filed	MASCOUTAH, CITY OF
NPDES ID	IL0025291
Permit status	Administratively continued (past its expiration date and still in force until reissued)
Permit type	Individual permit
Discharger class	Minor discharger
Facility type	Publicly owned treatment works
Program	Publicly owned treatment works
Issued	February 19, 2020
Expiration date	February 28, 2025
Address	Mascoutah, IL 62258
Receiving water	SILVER CREEK
Subwatershed	Scott Lake-Silver Creek (HUC 071402040510)
Program components on file	Biosolids, POTW
SIC	4952 – Sewerage Systems

Cited to the EPA ICIS-NPDES permit file (ECHO download) and EPA’s NAICS/SIC and component files, the same download.

Effluent limits and exceedances

34Pollutants on file
34Under a numeric limit
9With a violation of any kind
1With an effluent exceedance

An effluent exceedance is a discharge monitoring report value over the permit’s numeric limit (EPA’s violation code E90). A violation of any kind also counts a report not filed. Each row is EPA’s own count for that pollutant.

Pollutant or measure	Limits	Violations, any kind	Effluent exceedances	Latest exceedance	Largest exceedance, as filed
Solids, total suspended	20	32	1	June 30, 2013	4% over the limit
Nitrogen, ammonia total [as N]	128	28	0
Flow, in conduit or thru treatment plant	8	26	0
BOD, carbonaceous [5 day, 20 C]	16	24	0
Oxygen, dissolved [DO]	20	15	0
pH	8	12	0
BOD, 5-day, 20 deg. C	4	7	0
Chlorine, total residual	4	6	0
Coliform, fecal general	4	3	0
Phosphorus, total [as P]	8	0	0
Oil & Grease	2	0	0
Nitrogen, total [as N]	2	0	0
Cyanide, total [as CN]	2	0	0
Cyanide, free [amenable to chlorination]	2	0	0
Fluoride, total [as F]	2	0	0
Arsenic, total [as As]	2	0	0
Barium, total [as Ba]	2	0	0
Beryllium, total [as Be]	2	0	0
Cadmium, total [as Cd]	2	0	0
Chromium, hexavalent [as Cr]	2	0	0
Chromium, total [as Cr]	2	0	0
Copper, total [as Cu]	2	0	0
Iron, total [as Fe]	2	0	0
Iron, dissolved [as Fe]	2	0	0
Lead, total [as Pb]	2	0	0
Manganese, total [as Mn]	2	0	0
Thallium, total [as Tl]	2	0	0
Nickel, total [as Ni]	2	0	0
Silver, total [as Ag]	2	0	0
Zinc, total [as Zn]	2	0	0
Antimony, total [as Sb]	2	0	0
Selenium, total [as Se]	2	0	0
Phenolics, total recoverable	2	0	0
Mercury, total [as Hg]	2	0	0

Cited to the EPA ICIS-NPDES limits and effluent violations files (ECHO download); up to 60 rows shown, most exceedances first.

Inspections, violations and enforcement

9Single-event violations

Date	What EPA recorded	Agency
March 5, 2026	Dry-weather SSO, no discharge to waters of the U.S., that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6
April 4, 2025	Wet-weather SSO discharge to waters of the U.S. that may endanger health or the environment	ST6

Velarion’s copy of EPA’s ICIS-NPDES files does not include the inspections, formal enforcement actions and informal enforcement actions files, so this page shows none of them. EPA’s free Detailed Facility Report on ECHO lists this permit’s inspections, enforcement actions and penalties.

Cited to the EPA ICIS-NPDES violation, inspection and enforcement files (ECHO download); up to 50 rows of each shown, newest first.

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EPA publishes a free Detailed Facility Report for every permit on ECHO: its compliance status quarter by quarter, its inspections, and its enforcement actions and penalties. EPA also sends free notices of new inspections and enforcement actions through ECHO Notify; enter NPDES ID IL0025291 there.

Nearby on the register

Figures from EPA’s ICIS-NPDES download, loaded October 14, 2026.

This public-records page covers NPDES permit IL0025291 for MASCOUTAH STP, CITY OF in Mascoutah, IL, which discharges to Silver Creek within the Scott Lake-Silver Creek watershed (HUC 071402040510). The permit is listed as administratively continued, with a Minor Discharger class, 34 pollutants under a numeric limit, and 1 pollutant with an effluent exceedance.