MACKINAC ISLAND WWTP
NPDES ID: MI0026751
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: 6 effluent violations.
Violations
May 31, 2026
Mercury, total [as Hg]
120% over limit
Discharged 0.00003995 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
265% over limit
Discharged 0.00001823 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
April 30, 2026
BOD, 5-day, percent removal
38% over limit
Discharged 79.35 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
73% over limit
Discharged 0.00003133 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
188% over limit
Discharged 0.00001438 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Solids, suspended percent removal
268% over limit
Discharged 44.86 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
March 31, 2026
Solids, suspended percent removal
186% over limit
Discharged 57.08 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
BOD, 5-day, percent removal
22% over limit
Discharged 81.77 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
February 28, 2026
BOD, 5-day, 20 deg. C
53% over limit
Discharged 46 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Coliform, fecal general
10% over limit
Discharged 219 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
Solids, total suspended
244% over limit
Discharged 155 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, percent removal
95% over limit
Discharged 70.81 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
Solids, suspended percent removal
440% over limit
Discharged 18.95 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
110% over limit
Discharged 2.1 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
153% over limit
Discharged 76 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
January 31, 2026
Solids, suspended percent removal
13% over limit
Discharged 83 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
November 30, 2025
Chlorine, total residual
10% over limit
Discharged 0.55 mg/L against a permitted limit of 0.5 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
20% over limit
Discharged 1.2 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
190% over limit
Discharged 0.00001451 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
190% over limit
Discharged 0.00001451 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
October 31, 2025
Coliform, fecal general
36% over limit
Discharged 271 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
145% over limit
Discharged 0.00001224 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
80% over limit
Discharged 1.8 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
96% over limit
Discharged 88 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
37% over limit
Discharged 41 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
50% over limit
Discharged 0.00002724 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
8% over limit
Discharged 175.69799852 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
September 30, 2025
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
186% over limit
Discharged 0.0000143 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
186% over limit
Discharged 0.0000143 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Coliform, fecal general
39% over limit
Discharged 277 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
August 31, 2025
BOD, 5-day, 20 deg. C
36% over limit
Discharged 222.45999813 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
60% over limit
Discharged 72 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
18% over limit
Discharged 192.04199839 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
53% over limit
Discharged 69 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
55% over limit
Discharged 168.88799858 kg/d against a permitted limit of 108.95999908 kg/d (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000248 mg/L against a permitted limit of 0 mg/L (MO AVG)
DMR, Monitor Only - Overdue
Coliform, fecal general
8% over limit
Discharged 216 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
77% over limit
Discharged 0.00003223 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
77% over limit
Discharged 0.00003223 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000649 kg/d against a permitted limit of 0 kg/d (DAILY MX)
DMR, Monitor Only - Overdue
Solids, total suspended
17% over limit
Discharged 35 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000649 kg/d against a permitted limit of 0 kg/d (MO AVG)
DMR, Monitor Only - Overdue
Phosphorus, total [as P]
80% over limit
Discharged 1.8 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
28% over limit
Discharged 4.63079996 kg/d against a permitted limit of 3.63199997 kg/d (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
188% over limit
Discharged 0.00001439 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
188% over limit
Discharged 0.00001439 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
120% over limit
Discharged 66 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
July 31, 2025
BOD, 5-day, 20 deg. C
81% over limit
Discharged 296.00799751 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
50% over limit
Discharged 1.5 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
94% over limit
Discharged 211.10999823 kg/d against a permitted limit of 108.95999908 kg/d (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
142% over limit
Discharged 109 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00001875 kg/d against a permitted limit of 0 kg/d (MO AVG)
DMR, Monitor Only - Overdue
Mercury, total [as Hg]
0% over limit
Discharged 0.00000664 mg/L against a permitted limit of 0 mg/L (MO AVG)
DMR, Monitor Only - Overdue
BOD, 5-day, 20 deg. C
76% over limit
Discharged 79 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00001875 kg/d against a permitted limit of 0 kg/d (DAILY MX)
DMR, Monitor Only - Overdue
Mercury, total [as Hg]
189% over limit
Discharged 0.00001443 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
189% over limit
Discharged 0.00001443 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
75% over limit
Discharged 0.00003178 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
78% over limit
Discharged 290.55999756 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Phosphorus, total [as P]
15% over limit
Discharged 4.17679996 kg/d against a permitted limit of 3.63199997 kg/d (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
33% over limit
Discharged 40 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
160% over limit
Discharged 78 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
June 30, 2025
Mercury, total [as Hg]
0% over limit
Discharged 0.00000567 kg/d against a permitted limit of 0 kg/d (DAILY MX)
DMR, Monitor Only - Overdue
BOD, 5-day, 20 deg. C
60% over limit
Discharged 261.04999781 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
30% over limit
Discharged 39 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
65% over limit
Discharged 179.78399849 kg/d against a permitted limit of 108.95999908 kg/d (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
140% over limit
Discharged 72 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000279 mg/L against a permitted limit of 0 mg/L (MO AVG)
DMR, Monitor Only - Overdue
Coliform, fecal general
12% over limit
Discharged 223 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
68% over limit
Discharged 0.00003042 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
68% over limit
Discharged 0.00003042 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
118% over limit
Discharged 355.48199701 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
179% over limit
Discharged 0.00001396 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
179% over limit
Discharged 0.00001396 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000567 kg/d against a permitted limit of 0 kg/d (MO AVG)
DMR, Monitor Only - Overdue
BOD, 5-day, 20 deg. C
58% over limit
Discharged 71 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
273% over limit
Discharged 168 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
May 31, 2025
Mercury, total [as Hg]
65% over limit
Discharged 0.00002996 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
65% over limit
Discharged 0.00002996 kg/d against a permitted limit of 0.00001816 kg/d (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00031294 kg/d against a permitted limit of 0 kg/d (DAILY MX)
DMR, Monitor Only - Overdue
Mercury, total [as Hg]
177% over limit
Discharged 0.00001385 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
177% over limit
Discharged 0.00001385 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.000142 mg/L against a permitted limit of 0 mg/L (MO AVG)
DMR, Monitor Only - Overdue
Solids, total suspended
333% over limit
Discharged 195 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
95% over limit
Discharged 212.01799822 kg/d against a permitted limit of 108.95999908 kg/d (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
30% over limit
Discharged 142.10199881 kg/d against a permitted limit of 108.95999908 kg/d (MO AVG)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00031294 kg/d against a permitted limit of 0 kg/d (MO AVG)
DMR, Monitor Only - Overdue
Phosphorus, total [as P]
10% over limit
Discharged 1.1 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
200% over limit
Discharged 90 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
157% over limit
Discharged 420.40399647 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, suspended percent removal
40% over limit
Discharged 79 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
79% over limit
Discharged 292.82999754 kg/d against a permitted limit of 163.43999863 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
31% over limit
Discharged 59 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
123% over limit
Discharged 67 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, percent removal
13% over limit
Discharged 83 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
April 30, 2025
Mercury, total [as Hg]
0% over limit
Discharged 0.00000447 mg/L against a permitted limit of 0 mg/L (MO AVG)
DMR, Monitor Only - Overdue
Solids, suspended percent removal
100% over limit
Discharged 70 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000813 kg/d against a permitted limit of 0 kg/d (DAILY MX)
DMR, Monitor Only - Overdue
Mercury, total [as Hg]
0% over limit
Discharged 0.00000213 mg/L against a permitted limit of 0.000005 mg/L (12MO AVG)
DMR, Limited - Overdue
Mercury, total [as Hg]
0% over limit
Discharged 0.00000447 mg/L against a permitted limit of 0 mg/L (DAILY MX)
DMR, Monitor Only - Overdue
BOD, 5-day, percent removal
20% over limit
Discharged 82 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
Mercury, total [as Hg]
0% over limit
Discharged 0.00000813 kg/d against a permitted limit of 0 kg/d (MO AVG)
DMR, Monitor Only - Overdue
March 31, 2025
Solids, suspended percent removal
107% over limit
Discharged 69 % against a permitted limit of 85 % (MINIMUM)
DMR, Limited - Numeric Violation
February 28, 2025
Chlorine, total residual
20% over limit
Discharged 0.6 mg/L against a permitted limit of 0.5 mg/L (DAILY MX)
DMR, Limited - Numeric Violation
November 30, 2024
Phosphorus, total [as P]
50% over limit
Discharged 1.5 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
October 31, 2024
Phosphorus, total [as P]
20% over limit
Discharged 1.2 mg/L against a permitted limit of 1 mg/L (MO AVG)
DMR, Limited - Numeric Violation
September 30, 2024
Coliform, fecal general
40% over limit
Discharged 279 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
August 31, 2024
Solids, total suspended
29% over limit
Discharged 58 mg/L against a permitted limit of 45 mg/L (7 DA AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
1% over limit
Discharged 1.80908005 kg/d against a permitted limit of 1.78920005 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
30% over limit
Discharged 39 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
BOD, 5-day, 20 deg. C
27% over limit
Discharged 38 mg/L against a permitted limit of 30 mg/L (MO AVG)
DMR, Limited - Numeric Violation
Solids, total suspended
1% over limit
Discharged 1.79914005 kg/d against a permitted limit of 1.78920005 kg/d (7 DA AVG)
DMR, Limited - Numeric Violation
Coliform, fecal general
29% over limit
Discharged 257 MPN/100mL against a permitted limit of 200 MPN/100mL (MO GEOMN)
DMR, Limited - Numeric Violation
First flagged
April 14, 2026 (3 months ago)
Last confirmed
July 13, 2026 (23 days ago)