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City of Mackinac Island

Sewage treatment plant, major discharger, Mackinac Island, Michigan. NPDES permit MI0026751, in force until Oct 1, 2028. Last 12 months: over a limit 32 times (last September 2026), 2 required values missing, 1 of 12 reports late. Source: EPA ECHO, Oct 22, 2026.

Reports due
About 21 days after each period: outfall 001 form A monthly (30 values), outfall SLD form L yearly (42 values)
Renewal application due
Apr 4, 2028 · 180 days before expiry; your permit may set another date
Last report on file
September 2026
Oct 2024 – Sep 2025
65 values over a limit, 27 required values missing, 6 of 13 reports late

Last 12 months (Oct 1, 2025 – Sep 30, 2026)

All 32 values over a limit
Period endingParameterReportedLimitOver by
October 2025Coliform, fecal general, monthly geometric mean271≤ 200 #/100mL36%
October 2025Mercury, total [as Hg], 12-month average.00006≤ .00004 lb/d50%
October 2025Mercury, total [as Hg], 12-month average12.242≤ 5 ng/L145%
October 2025Phosphorus, total [as P], monthly average1.8≤ 1 mg/L80%
October 2025Solids, total suspended, 7-day average387≤ 360 lb/d8%
October 2025Solids, total suspended, 7-day average88≤ 45 mg/L96%
October 2025Solids, total suspended, monthly average41≤ 30 mg/L37%
November 2025Chlorine, total residual, daily maximum.55≤ .5 mg/L10%
November 2025Mercury, total [as Hg], 12-month average.00007≤ .00004 lb/d75%
November 2025Mercury, total [as Hg], 12-month average.00007≤ .00004 lb/d75%
November 2025Mercury, total [as Hg], 12-month average14.513≤ 5 ng/L190%
November 2025Mercury, total [as Hg], 12-month average14.513≤ 5 ng/L190%
November 2025Phosphorus, total [as P], monthly average1.2≤ 1 mg/L20%
January 2026Solids, suspended percent removal, minimum83≥ 85 %13%
February 2026BOD, 5-day, 20 deg. C, monthly average46≤ 30 mg/L53%
February 2026BOD, 5-day, percent removal, minimum70.81≥ 85 %95%
February 2026Coliform, fecal general, monthly geometric mean219≤ 200 #/100mL10%
February 2026Phosphorus, total [as P], monthly average2.1≤ 1 mg/L110%
February 2026Solids, suspended percent removal, minimum18.95≥ 85 %440%
February 2026Solids, total suspended, 7-day average155≤ 45 mg/L244%
February 2026Solids, total suspended, monthly average76≤ 30 mg/L153%
March 2026BOD, 5-day, percent removal, minimum81.77≥ 85 %22%
March 2026Solids, suspended percent removal, minimum57.08≥ 85 %186%
April 2026BOD, 5-day, percent removal, minimum79.35≥ 85 %38%
April 2026Mercury, total [as Hg], 12-month average.000069≤ .00004 lb/d73%
April 2026Mercury, total [as Hg], 12-month average14.379≤ 5 ng/L188%
April 2026Solids, suspended percent removal, minimum44.86≥ 85 %268%
May 2026Mercury, total [as Hg], 12-month average.000088≤ .00004 lb/d120%
May 2026Mercury, total [as Hg], 12-month average18.234≤ 5 ng/L265%
August 2026Solids, total suspended, 7-day average387≤ 360 lb/d8%
August 2026Solids, total suspended, 7-day average54≤ 45 mg/L20%
September 2026Phosphorus, total [as P], monthly average1.14≤ 1 mg/L14%

Limits in force (72)

ParameterStatisticLimitMonthsOutfall
Oxygen, dissolved [DO]daily minimum≥ 4 mg/Lall year001
BOD, 5-day, 20 deg. Cmonthly average≤ 30 mg/Lall year001
BOD, 5-day, 20 deg. C7-day average≤ 45 mg/Lall year001
BOD, 5-day, 20 deg. Cmonthly average≤ 240 lb/dall year001
BOD, 5-day, 20 deg. C7-day average≤ 360 lb/dall year001
pHdaily minimum≥ 6.5 SUall year001
pHdaily maximum≤ 9 SUall year001
Solids, total suspendedmonthly average≤ 30 mg/Lall year001
Solids, total suspended7-day average≤ 45 mg/Lall year001
Solids, total suspendedmonthly average≤ 240 lb/dall year001
Solids, total suspended7-day average≤ 360 lb/dall year001
Phosphorus, total [as P]monthly average≤ 1 mg/Lall year001
Phosphorus, total [as P]daily maximumreport only (mg/L)all year001
Phosphorus, total [as P]monthly average≤ 8 lb/dall year001
Phosphorus, total [as P]daily maximumreport only (lb/d)all year001
Flow, in conduit or thru treatment plantmonthly averagereport only (MGD)all year001
Flow, in conduit or thru treatment plantdaily maximumreport only (MGD)all year001
Chlorine, total residualdaily maximum≤ .5 mg/Lall year001
Mercury, total [as Hg]monthly averagereport only (ng/L)Apr–Nov001
Mercury, total [as Hg]daily maximumreport only (ng/L)Apr–Nov001
Mercury, total [as Hg]monthly averagereport only (lb/d)Apr–Nov001
Mercury, total [as Hg]daily maximumreport only (lb/d)Apr–Nov001
Mercury, total [as Hg]12-month average≤ 5 ng/LApr–Nov001
Mercury, total [as Hg]12-month average≤ .00004 lb/dApr–Nov001
Coliform, fecal generalmonthly geometric mean≤ 200 #/100mLall year001
Coliform, fecal general7-day geometric mean≤ 400 #/100mLall year001
BOD, 5-day, percent removalminimum≥ 85 %all year001
BOD, 5-day, percent removaldaily minimumreport only (%)all year001
Solids, suspended percent removalminimum≥ 85 %all year001
Solids, suspended percent removaldaily minimumreport only (%)all year001
Solids, totalmonthly minimumreport only (%)all yearSLD
Solids, totalmonthly averagereport only (%)all yearSLD
Solids, totalmonthly maximumreport only (%)all yearSLD
Arsenic, dry weightmonthly minimumreport only (mg/kg)all yearSLD
Arsenic, dry weightmonthly averagereport only (mg/kg)all yearSLD
Arsenic, dry weightmonthly maximum≤ 75 mg/kgall yearSLD
Selenium, dry weightmonthly minimumreport only (mg/kg)all yearSLD
Selenium, dry weightmonthly averagereport only (mg/kg)all yearSLD
Selenium, dry weightmonthly maximum≤ 100 mg/kgall yearSLD
Copper, dry weightmonthly minimumreport only (mg/kg)all yearSLD
Copper, dry weightmonthly averagereport only (mg/kg)all yearSLD
Copper, dry weightmonthly maximum≤ 4300 mg/kgall yearSLD
Cadmium, dry weightmonthly minimumreport only (mg/kg)all yearSLD
Cadmium, dry weightmonthly averagereport only (mg/kg)all yearSLD
Cadmium, dry weightmonthly maximum≤ 85 mg/kgall yearSLD
Nitrogen, total Kjeldahlmonthly minimumreport only (mg/kg)all yearSLD
Nitrogen, total Kjeldahlmonthly averagereport only (mg/kg)all yearSLD
Nitrogen, total Kjeldahlmonthly maximumreport only (mg/kg)all yearSLD
Molybdenum, sludge, total, dry weight [as Mo]monthly minimumreport only (mg/kg)all yearSLD
Molybdenum, sludge, total, dry weight [as Mo]monthly averagereport only (mg/kg)all yearSLD
Molybdenum, sludge, total, dry weight [as Mo]monthly maximum≤ 75 mg/kgall yearSLD
Zinc, sludge, total, dry weight [as Zn]monthly minimumreport only (mg/kg)all yearSLD
Zinc, sludge, total, dry weight [as Zn]monthly averagereport only (mg/kg)all yearSLD
Zinc, sludge, total, dry weight [as Zn]monthly maximum≤ 7500 mg/kgall yearSLD
Lead, sludge, total, dry weight [as Pb]monthly minimumreport only (mg/kg)all yearSLD
Lead, sludge, total, dry weight [as Pb]monthly averagereport only (mg/kg)all yearSLD
Lead, sludge, total, dry weight [as Pb]monthly maximum≤ 840 mg/kgall yearSLD
Nickel, sludge, total, dry weight [as Ni]monthly minimumreport only (mg/kg)all yearSLD
Nickel, sludge, total, dry weight [as Ni]monthly averagereport only (mg/kg)all yearSLD
Nickel, sludge, total, dry weight [as Ni]monthly maximum≤ 420 mg/kgall yearSLD
Nitrogen, sludge, total, dry weight [as N]monthly minimumreport only (mg/kg)all yearSLD
Nitrogen, sludge, total, dry weight [as N]monthly averagereport only (mg/kg)all yearSLD
Nitrogen, sludge, total, dry weight [as N]monthly maximumreport only (mg/kg)all yearSLD
Mercury, sludge, total, dry weight [as Hg]monthly minimumreport only (mg/kg)all yearSLD
Mercury, sludge, total, dry weight [as Hg]monthly averagereport only (mg/kg)all yearSLD
Mercury, sludge, total, dry weight [as Hg]monthly maximum≤ 57 mg/kgall yearSLD
Potassium, sludge, total, dry weight [as K]monthly minimumreport only (mg/kg)all yearSLD
Potassium, sludge, total, dry weight [as K]monthly averagereport only (mg/kg)all yearSLD
Potassium, sludge, total, dry weight [as K]monthly maximumreport only (mg/kg)all yearSLD
Phosphorus, sludge, total, dry weight [as P]monthly minimumreport only (mg/kg)all yearSLD
Phosphorus, sludge, total, dry weight [as P]monthly averagereport only (mg/kg)all yearSLD
Phosphorus, sludge, total, dry weight [as P]monthly maximumreport only (mg/kg)all yearSLD

How strict are these limits?

Cited limits by parameter: Michigan's rules and the federal ones.

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On EPA ECHO: Facility report · DMR history

Your permit document is the final word. As JSON: /api/v1/permits/MI0026751 · MCP: https://passage-data.com/mcp