MARENGO CITY OF STP
NPDES ID: IA0047937
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: 5 effluent violations, 3 reporting violations.
Violations
May 31, 2026
Oxygen, dissolved [DO]
59% over limit
Discharged 2.03 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
April 30, 2026
pH
0% over limit
Discharged 0 SU against a permitted limit of 6.5 SU (DAILY MN)
DMR, Limited - Overdue
pH
0% over limit
Discharged 0 SU against a permitted limit of 9 SU (DAILY MX)
DMR, Limited - Overdue
Nitrogen, ammonia total [as N]
107% over limit
Discharged 47.989434 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
15% over limit
Discharged 21.8 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
89% over limit
Discharged 32.54288771 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
0% over limit
Discharged 0 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Overdue
Nitrogen, ammonia total [as N]
16% over limit
Discharged 16.2475 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
March 31, 2026
Nitrogen, ammonia total [as N]
66% over limit
Discharged 23.275 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
36% over limit
Discharged 25.9 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
January 31, 2026
Oxygen, dissolved [DO]
18% over limit
Discharged 4.12 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
December 31, 2025
Oxygen, dissolved [DO]
36% over limit
Discharged 3.2 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
61% over limit
Discharged 22.54 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
38% over limit
Discharged 26.2 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
24% over limit
Discharged 28.76876304 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
5% over limit
Discharged 18.19759559 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
November 30, 2025
Nitrogen, ammonia total [as N]
18% over limit
Discharged 16.475 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
34% over limit
Discharged 3.29 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
October 31, 2025
Oxygen, dissolved [DO]
83% over limit
Discharged 0.86 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
pH
0% over limit
Discharged 6.48 SU against a permitted limit of 6.5 SU (DAILY MN)
DMR, Limited - Numeric Violation
September 30, 2025
Nitrogen, ammonia total [as N]
2% over limit
Discharged 14.3 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
78% over limit
Discharged 1.1 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
August 31, 2025
Nitrogen, ammonia total [as N]
1% over limit
Discharged 17.04358208 kg/d against a permitted limit of 16.79799986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
19% over limit
Discharged 26.98549645 kg/d against a permitted limit of 22.69999981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
66% over limit
Discharged 1.69 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
July 31, 2025
Nitrogen, ammonia total [as N]
47% over limit
Discharged 33.3932524 kg/d against a permitted limit of 22.69999981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
52% over limit
Discharged 25.45545745 kg/d against a permitted limit of 16.79799986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
48% over limit
Discharged 17.8 mg/L against a permitted limit of 12 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
18% over limit
Discharged 22.4 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
83% over limit
Discharged 0.87 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
June 30, 2025
Oxygen, dissolved [DO]
83% over limit
Discharged 0.84 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
35% over limit
Discharged 25.6 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
71% over limit
Discharged 24 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
May 31, 2025
Nitrogen, ammonia total [as N]
76% over limit
Discharged 24.7 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
55% over limit
Discharged 29.4 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
42% over limit
Discharged 2.9 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
33% over limit
Discharged 22.97239981 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
25% over limit
Discharged 29.01059976 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
April 30, 2025
Nitrogen, ammonia total [as N]
86% over limit
Discharged 26.04 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
42% over limit
Discharged 24.56030565 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
61% over limit
Discharged 1.95 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
65% over limit
Discharged 38.1294984 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
47% over limit
Discharged 27.9 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
March 31, 2025
Nitrogen, ammonia total [as N]
26% over limit
Discharged 21.70065048 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
55% over limit
Discharged 29.5 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
82% over limit
Discharged 25.475 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
28% over limit
Discharged 29.74736457 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
February 28, 2025
BOD, carbonaceous [5 day, 20 C]
0% over limit
Discharged 0 mg/L against a permitted limit of 25 mg/L (30DA AVG)
DMR, Limited - Overdue
Solids, total suspended
0% over limit
Discharged 0 mg/L against a permitted limit of 120 mg/L (7 DA AVG)
DMR, Limited - Overdue
Solids, total suspended
0% over limit
Discharged 0 mg/L against a permitted limit of 80 mg/L (30DA AVG)
DMR, Limited - Overdue
Solids, total suspended
0% over limit
Discharged 0 kg/d against a permitted limit of 166.1639986 kg/d (30DA AVG)
DMR, Limited - Overdue
Solids, total suspended
0% over limit
Discharged 0 kg/d against a permitted limit of 249.24599791 kg/d (7 DA AVG)
DMR, Limited - Overdue
BOD, carbonaceous [5 day, 20 C]
0% over limit
Discharged 0 mg/L against a permitted limit of 40 mg/L (7 DA AVG)
DMR, Limited - Overdue
BOD, carbonaceous [5 day, 20 C]
0% over limit
Discharged 0 kg/d against a permitted limit of 83.0819993 kg/d (7 DA AVG)
DMR, Limited - Overdue
BOD, carbonaceous [5 day, 20 C]
0% over limit
Discharged 0 kg/d against a permitted limit of 52.20999956 kg/d (30DA AVG)
DMR, Limited - Overdue
January 31, 2025
Oxygen, dissolved [DO]
21% over limit
Discharged 3.97 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
December 31, 2024
Nitrogen, ammonia total [as N]
78% over limit
Discharged 33.8 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
12% over limit
Discharged 25.96626192 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
56% over limit
Discharged 2.2 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
126% over limit
Discharged 31.65 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
29% over limit
Discharged 22.25791731 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
November 30, 2024
Nitrogen, ammonia total [as N]
122% over limit
Discharged 31.025 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
151% over limit
Discharged 58.22913151 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
39% over limit
Discharged 3.05 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
97% over limit
Discharged 33.99492497 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
77% over limit
Discharged 33.7 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
October 31, 2024
Nitrogen, ammonia total [as N]
8% over limit
Discharged 25.08891147 kg/d against a permitted limit of 23.15399981 kg/d (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
73% over limit
Discharged 1.35 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
119% over limit
Discharged 41.7 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
3% over limit
Discharged 17.74389069 kg/d against a permitted limit of 17.25199986 kg/d (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
152% over limit
Discharged 35.26 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
September 30, 2024
Oxygen, dissolved [DO]
80% over limit
Discharged 0.98 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
88% over limit
Discharged 26.325 mg/L against a permitted limit of 14 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
81% over limit
Discharged 34.3 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
August 31, 2024
Nitrogen, ammonia total [as N]
37% over limit
Discharged 16.385 mg/L against a permitted limit of 12 mg/L (30DA AVG)
DMR, Limited - Numeric Violation
Nitrogen, ammonia total [as N]
15% over limit
Discharged 21.8 mg/L against a permitted limit of 19 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Oxygen, dissolved [DO]
86% over limit
Discharged 0.71 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
July 31, 2024
Oxygen, dissolved [DO]
89% over limit
Discharged 0.54 mg/L against a permitted limit of 5 mg/L (DAILY MN)
DMR, Limited - Numeric Violation
First flagged
April 14, 2026 (3 months ago)
Last confirmed
July 13, 2026 (23 days ago)