HILLSBORO STP, CITY OF
NPDES ID: IL0029203
E — SNC: Effluent violation (monthly average limit)
The facility discharged more of a pollutant than its permit allows, based on a monthly average.
This quarter: 6 effluent violations, 4 permit schedule violations.
Violations
May 31, 2026
Solids, total suspended
56% over limit
Discharged 18.66 mg/L against a permitted limit of 12 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
25% over limit
Discharged 30.1 mg/L against a permitted limit of 24 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
April 30, 2026
BOD, carbonaceous [5 day, 20 C]
10% over limit
Discharged 10.98 mg/L against a permitted limit of 10 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
20% over limit
Discharged 3.61 mg/L against a permitted limit of 3 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
47% over limit
Discharged 2.2 mg/L against a permitted limit of 1.5 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
13% over limit
Discharged 39.35271967 kg/d against a permitted limit of 34.95799971 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
March 31, 2026
Nitrogen, ammonia total [as N]
28% over limit
Discharged 5.62 mg/L against a permitted limit of 4.4 mg/L (WKLY AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
56% over limit
Discharged 8.09 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
BOD, carbonaceous [5 day, 20 C]
30% over limit
Discharged 13.01 mg/L against a permitted limit of 10 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
111% over limit
Discharged 3.37 mg/L against a permitted limit of 1.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
34% over limit
Discharged 16.08 mg/L against a permitted limit of 12 mg/L (MO AVG)
DMR, Limited - Numeric Violation
February 28, 2026
BOD, carbonaceous [5 day, 20 C]
80% over limit
Discharged 17.97 mg/L against a permitted limit of 10 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
69% over limit
Discharged 8.8 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
BOD, carbonaceous [5 day, 20 C]
31% over limit
Discharged 26.2 mg/L against a permitted limit of 20 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Solids, total suspended
16% over limit
Discharged 13.9 mg/L against a permitted limit of 12 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
106% over limit
Discharged 5.36 mg/L against a permitted limit of 2.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Coliform, fecal general
1353% over limit
Discharged 5810 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
January 31, 2026
BOD, carbonaceous [5 day, 20 C]
21% over limit
Discharged 12.05 mg/L against a permitted limit of 10 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
106% over limit
Discharged 10.7 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
87% over limit
Discharged 4.87 mg/L against a permitted limit of 2.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
December 31, 2025
Nitrogen, ammonia total [as N]
17% over limit
Discharged 6.08 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
March 31, 2025
1H,1H, 2H, 2H-Perfluorodecane sulfonic acid (8:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
1H,1H,2H,2H-Perfluorohexane sulfonic acid (4:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
1H,1H,2H,2H-Perfluorooctane sulfonic acid (6:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
1H,1H,2H,2H-Perfluorohexane sulfonic acid (4:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
1H,1H,2H,2H-Perfluorooctane sulfonic acid (6:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
1H,1H, 2H, 2H-Perfluorodecane sulfonic acid (8:2 FTS)
0% over limit
Discharged 0 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
Nitrogen, ammonia total [as N]
42% over limit
Discharged 2.27 mg/L against a permitted limit of 1.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
January 31, 2025
Nitrogen, ammonia total [as N]
42% over limit
Discharged 3.7 mg/L against a permitted limit of 2.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
9% over limit
Discharged 13.1 mg/L against a permitted limit of 12 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
10% over limit
Discharged 5.7 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
December 31, 2024
Nitrogen, ammonia total [as N]
23% over limit
Discharged 3.2 mg/L against a permitted limit of 2.6 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
34% over limit
Discharged 6.95 mg/L against a permitted limit of 5.2 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
July 31, 2024
Coliform, fecal general
1235% over limit
Discharged 5340 MPN/100mL against a permitted limit of 400 MPN/100mL (DAILY MX)
DMR, Limited - Numeric Violation
First flagged
April 14, 2026 (3 months ago)
Last confirmed
July 13, 2026 (22 days ago)