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, 1 single-event violation, 4 permit schedule 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
First flagged
April 14, 2026 (5 months ago)
Last confirmed
September 15, 2026 (4 days ago)