ALTON STP, CITY OF
NPDES ID: IL0027464
X — SNC: Effluent violation (non-monthly average limit)
The facility discharged more of a pollutant than its permit allows, measured over a period other than a monthly average.
This quarter: 3 effluent violations, 1 single-event violation.
Violations
June 30, 2026
Chlorine, total residual
119% over limit
Discharged 1.64 mg/L against a permitted limit of 0.75 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
May 31, 2026
Coliform, fecal general
Limit violation
Discharged 2419.6 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
April 30, 2026
Chlorine, total residual
108% over limit
Discharged 1.56 mg/L against a permitted limit of 0.75 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
August 31, 2025
Coliform, fecal general
333% over limit
Discharged 1732.9 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
Solids, total suspended
9% over limit
Discharged 49.15 mg/L against a permitted limit of 45 mg/L (WKLY AVG)
DMR, Limited - Numeric Violation
July 31, 2025
Coliform, fecal general
505% over limit
Discharged 2419.6 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
June 30, 2025
Coliform, fecal general
29% over limit
Discharged 517.2 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
May 31, 2025
Coliform, fecal general
31% over limit
Discharged 524.7 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
Chlorine, total residual
36% over limit
Discharged 1.02 mg/L against a permitted limit of 0.75 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
April 30, 2025
Fluoride, total [as F]
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
October 31, 2024
Coliform, fecal general
505% over limit
Discharged 2419.6 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
September 30, 2024
Chlorine, total residual
35% over limit
Discharged 1.01 mg/L against a permitted limit of 0.75 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Coliform, fecal general
2202% over limit
Discharged 9208 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
August 31, 2024
Chlorine, total residual
15% over limit
Discharged 0.86 mg/L against a permitted limit of 0.75 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
First flagged
April 14, 2026 (4 months ago)
Last confirmed
August 15, 2026 (4 hours ago)