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Michigan / Sewer operators /

City of Ann Arbor

Sewer operator · Michigan · Ann Arbor

Map sources: water outlines and launches from OpenBoatLaunch and OpenStreetMap contributors (Open Database License); wastewater outlets from EPA and state records; downstream estimates by DirtyWaterWatch using U.S. Geological Survey maps and flow data. Base map: OpenFreeMap and OpenMapTiles.

Ringed dots mark treatment plant outfalls. Square boat markers mark boat launches listed by OpenBoatLaunch.

Federal wastewater discharge permit (NPDES)
MI0022217, 3112a-0724
Wastewater outlets
2 treatment plant outfalls listed by EPA or state agencies; no combined sewer outfall is listed · List
Waters listed as receiving wastewater
Huron River
Tracked waters
Huron River, MI
Discharge records counted
26 records · latest
Total reported volume in these records
1,478,065 gallons across the 26 records that give a volume

These totals reflect the records we track. Missing volumes and gaps in reporting limit comparisons between operators.

Sources: EPA ECHO and the operator and state sources linked below. Counts use the discharge records on this page. Updated 2026-11-05 01:25 UTC.

Public notices and alerts

Pages where City of Ann Arbor or the state publishes its notices (check them for an alert sign-up):

Its public-notice channels

Source: City of Ann Arbor's public notice and alert pages and the state's notification records; DirtyWaterWatch register of public-notice channels and its page monitor.

Report a missing notice or error

Wastewater outlets

Outfall: a pipe or outlet where wastewater enters a water body.

2 treatment plant outfalls listed by EPA or state agencies; no combined sewer outfall is listed.

Treatment plant outfalls

2 outfalls

Source: U.S. Environmental Protection Agency (EPA) permit records (ICIS-NPDES permitted features): where a treatment plant’s permitted discharge leaves. No national source says whether a plant outfall is open or closed.

Reports and advisories

Sanitary sewer overflow (SSO): sewage spills from a sewer meant to carry sewage separately from rainwater. Treatment bypass: wastewater skips one or more treatment steps.

Reports linked to City of Ann Arbor, newest first
WhenReportStatus
Huron River · SSO · 120 gallons report · notice · mapended
Huron River · SSO · 5 gallons report · notice · mapended
to 1:00 PM“private retention pond” · 71-63612 - city-owned sanitary manhole · SSO · 50 gallons report · noticeended
to 2:00 PMWater not mapped · 71-70439 - City-owned manhole · SSO · 5 gallons report · noticeended
to 9:00 PM“Allen Creek” · Manhole in intersection of South Main Street and Madison. · SSO · 8,400 gallons report · noticeended
to 1:15 AM“Malletts Creek” · Fair Oaks Road - manhole lid (71-69430) · SSO · 300 gallons report · noticeended
to 10:23 AM“Malletts Creek” · Mh71-63127 · SSO · 450 gallons report · noticeended
“Swift Run Drain” · storm drain, u/s of Swift Run Drain - Swift Run Drain · SSO · 75 gallons report · noticeended
to 9:00 PMWater not mapped · Private Residence Address - sanitary manhole (MH71-70533) · SSO · 400 gallons report · noticeended
to Sep 28 ’23, 4:00 PMWater not mapped · Private Residence Address - grassy area · SSO · 10 gallons report · noticeended
to 3:30 PMWater not mapped · corner of South State Street and Monroe Street · SSO · 5 gallons report · noticeended
to Jun 9 ’23, 9:00 AMWater not mapped · near [house number removed] Kuehnle - gravel road ROW near [house number removed] Kuehnle · SSO · 10 gallons report · noticeended
to 2:30 PM“Mallets Creek” · MH - 71-72077 - City owned sanitary sewer manhole. · SSO · 200 gallons report · noticeended
to 2:00 PMHuron River · Huron River - Normal WWTP discharge location. · Bypass · 1.38 million gallons report · notice · mapended
to 5:00 PMWater not mapped · Private Residence Address - Wooded area behind home · SSO · 935 gallons report · noticeended
to 11:30 AMWater not mapped · Sequoia Lift Station · SSO · 1,870 gallons report · noticeended
to Aug 11 ’21, 2:00 PM“Swift Run Drain” · Private Residence Address - cleanout cap of private lead · SSO · 50 gallons report · noticeended
to 2:00 PM“Allen Creek” · 71-71681 - manhole at Jefferson & Ashley · SSO · 60 gallons report · noticeended
to 9:40 AMWater not mapped · 71-70046 - open grassy area · SSO · 600 gallons report · noticeended
to 12:00 PMWater not mapped · Private Residence Address - cleanout of private sewer lead · SSO · 10 gallons report · noticeended
to 12:30 PMWater not mapped · 71-69271 - manhole in UM Arboretum · SSO · 500 gallons report · noticeended
to 2:30 PMHuron River · Main Street/Madison - bypass pumping operations - no outfall · SSO · 10,000 gallons report · notice · mapended
to 10:15 AMHuron River · Ann Arbor WWTP Equalization/Retention Building overflow - [house number removed] Old Dixboro Road, Ann Arbor, MI 48105 · Bypass · 1,000 gallons report · notice · mapended
to 1:20 PMHuron River · Allen Creek - Allen Creek outfall to Huron River · SSO · 3,000 gallons report · notice · mapended
to 6:10 AMHuron River · WWTP East Plant Stormwater - Stormwater outfall to the Huron River · Bypass · 75,000 gallons report · notice · mapended

Sources: EGLE MiEnviro CSO/SSO List, retrieved 2026-11-04 15:09 UTC. A report's record id and times show when you hover or focus its "report" link.

Download these reports as CSV

Showing the latest 25 records of 26 records.See them all with filters.

All reports in Michigan by year: 2025 (6 from City of Ann Arbor) · 2024 (3 from City of Ann Arbor) · 2023 (3 from City of Ann Arbor) · 2022 (4 from City of Ann Arbor) · 2021 (6 from City of Ann Arbor) · 2020 (1 from City of Ann Arbor) · 2019 (3 from City of Ann Arbor)

Other sewer operators on these waters

The last 90 days

Last 90 days, hour by hour. Red: discharge or advisory reported. Amber: caution. Hatched amber: end not confirmed. Plum: algal bloom advisory. Red or amber with a light line inside: beach advisory or caution. Dotted: monthly report (days with discharge, dates not given). Grey: no current status on the water outline. Purple hatching: source update overdue.

No discharge, advisory or caution periods are shown for the waters this sewer operator's reports were placed on in this time span. Check downstream stretches and source coverage.

Source: DirtyWaterWatch calculations using the reports named above and the published status rules. Updated 2026-11-05 01:25 UTC.

Reported discharges over time

  • Discharges reported by City of Ann Arbor, last 12 months1December 2025 to November 2026Verified reports where available, else notices; revisions and duplicates counted once.
  • Days with a discharge reported by City of Ann Arbor, last 12 months1December 2025 to November 2026A day counts once however many discharges were under way on it.
  • Hours with a discharge or advisory status from City of Ann Arbor's reports, last 12 months0December 2025 to November 2026Red hours by the map's rules: each discharge to its reported end plus the state's post-discharge period; overlapping hours count once.
  • 2026 season with a discharge or advisory status (City of Ann Arbor)0.0%May to October 2026Share of May 1 to October 31 hours with red status by the map's rules, of the hours a source covered.

Combined sewer overflow (CSO): sewage mixed with rainwater spills from a shared sewer system. Blended discharge: wastewater that skipped some treatment is mixed with treated wastewater.

Reported discharges per month

16 reported discharges, January 2022 to November 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Treatment bypass, blended or other

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2022 to November 4, 2026.

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Hours with a discharge or advisory status per month

Hours when a water had a discharge or advisory status from this sewer operator's reports, under DirtyWaterWatch rules.

  • Discharge or advisory reported

3 discharge reports have no end time and are not marked ongoing; under DirtyWaterWatch rules they show caution, not a discharge or advisory status, and add no hours here. Official beach and cyanobacteria (harmful blue-green algae) advisories are counted on water pages only.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Days with a reported discharge per month

A day counts when any counted discharge was under way on it, from its start to its reported end in Eastern Time; a report with no end counts its start day.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2022 to November 4, 2026.

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Reported discharges per year, 2001 to 2026

26 reported discharges, 2001 to 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Treatment bypass, blended or other

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Reported volume per year

Gallons (axis: K thousand, M million), summed from the 26 reports that gave a volume as a number.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Hours with a discharge or advisory status per year

Hours with a discharge or advisory status each year under DirtyWaterWatch rules; 2026 to date.

  • Discharge or advisory reported

3 discharge reports have no end time and are not marked ongoing; under DirtyWaterWatch rules they show caution, not a discharge or advisory status, and add no hours here. Official beach and cyanobacteria (harmful blue-green algae) advisories are counted on water pages only.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Share of the May to October season with a discharge or advisory status

Share of the hours from May 1 to October 31 with a discharge or advisory status under DirtyWaterWatch rules.

  • Discharge or advisory reported

3 discharge reports have no end time and are not marked ongoing; under DirtyWaterWatch rules they show caution, not a discharge or advisory status, and add no hours here. Official beach and cyanobacteria (harmful blue-green algae) advisories are counted on water pages only.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Reported discharges by calendar month, all years

Every counted discharge report, by the calendar month it began.

Months are summed over every year a tracked source covers; the table gives the number of years behind each month.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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Reported discharges by wastewater outlet

Wastewater outlets with the most tracked discharge records: 10 of 24, all years. Counts depend on reporting coverage and do not measure legal compliance or harm.

Source: mi-egle-mienviro-cso-sso-list. Records cover January 1, 2001 to November 4, 2026.

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How these charts are counted

We count each discharge once. Where a source publishes notices and confirmed reports, we use confirmed reports for an operator's month when available; otherwise we use notices. We combine revisions and exclude duplicate state reports copied by the U.S. Environmental Protection Agency (EPA). Monthly and yearly totals appear separately. Status hours follow this site's rules. Shaded gaps mean missing coverage, not zero discharges.

  • mi-egle-mienviro-cso-sso-list: records from January 1, 2001 to the latest update