DirtyWaterWatch

Connecticut / Waters /

Mystic River

River in Connecticut · near Groton, Mystic, Stonington

Status now

No current report

At least one source we follow covers this water, and nothing it reports applies right now.

Why this colour: No current report: nothing a covering source reports colours this water now. How long a water stays coloured, and why

Source: CT DEEP CSO/SSO Performance Dashboard (QScend), last answered 2026-11-02 11:53 UTC; ct-deep-annual, last answered 2026-11-02 11:54 UTC; ct-deep-archive, last answered 2026-11-02 11:54 UTC. Status computed by DirtyWaterWatch as of 2026-11-02 11:56 UTC.

It is not a finding about the water. Discharges go unreported, reports arrive late, and storm runoff carries bacteria too. Follow posted signs and local health advice.

Rivers are not coloured as a whole: a discharge colours a modeled stretch downstream of its outfall, listed below when there is one.

As of Nov 2, 2026, 6:56 AM EST.

Map

Source: water outlines from OpenBoatLaunch and OpenStreetMap contributors (ODbL); outfalls from EPA ECHO and the state outfall layers; modeled reaches computed by DirtyWaterWatch from USGS NLDI, NHDPlus and the nearest USGS gauge (Jobson 1996); basemap OpenFreeMap and OpenMapTiles.

Outfalls are small brown dots.

Modeled downstream reaches on Mystic River

No discharge colours a modeled reach on this water now.

The last 90 days

Last 90 days, hour by hour. Red: advisory in effect; yellow: caution; hatched yellow: unresolved, no end reported; grey: no current report; hatched purple: a source was not updating.

No red or yellow period in this span.

Source: hourly statuses computed by DirtyWaterWatch (pipeline build/status.py) from the events linked above and the rules on the methods page; history as of 2026-11-02 11:56 UTC.

Discharges over the years

  • Discharge events, last 12 months1Dec 2025 to Nov 2026
  • Days with a discharge, last 12 months1Dec 2025 to Nov 2026
  • Hours under advisory, last 12 months0Dec 2025 to Nov 2026
  • 2026 season under advisory0.0%May to October; 0 h

Discharge events per month

2 events, Jan 2022 to Nov 2026. Counted from 1 verified or annual reports, 1 public notices.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Bypass, blended or other

CT DEEP dashboard records begin 2021-12-02; where CT DEEP's annual report covers a discharger's month, the annual report is counted instead. CT DEEP annual reports (Sewage Right-to-Know) cover 2021-01-01 to 2026-11-02.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports. Covered 2022-01-01 to 2026-11-02.

Show table
Discharge events per month
MonthCombined sewer overflowSanitary sewer overflowBypass, blended or otherTotalCounted fromCoverage
Jan 20220000
Feb 20220000
Mar 20220000
Apr 20220000
May 20220000
Jun 20220000
Jul 20220000
Aug 20220000
Sep 20220000
Oct 20220000
Nov 20220000
Dec 20220000
Jan 20230000
Feb 20230000
Mar 20230000
Apr 20230000
May 20230000
Jun 20230000
Jul 20230000
Aug 20230000
Sep 20230000
Oct 20230000
Nov 20230000
Dec 20230000
Jan 20240011Verified or annual reports
Feb 20240000
Mar 20240000
Apr 20240000
May 20240000
Jun 20240000
Jul 20240000
Aug 20240000
Sep 20240000
Oct 20240000
Nov 20240000
Dec 20240000
Jan 20250000
Feb 20250000
Mar 20250000
Apr 20250000
May 20250000
Jun 20250000
Jul 20250000
Aug 20250000
Sep 20250000
Oct 20250000
Nov 20250000
Dec 20250000
Jan 20260000
Feb 20260000
Mar 20260000
Apr 20260101Public notices (no report yet)
May 20260000
Jun 20260000
Jul 20260000
Aug 20260000
Sep 20260000
Oct 20260000
Nov 20260000

Hours under advisory per month

Hours this water was under an advisory, by the map's red rules.

  • Advisory in effect

1 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here. CT DEEP dashboard records begin 2021-12-02; where CT DEEP's annual report covers a discharger's month, the annual report is counted instead. CT DEEP annual reports (Sewage Right-to-Know) cover 2021-01-01 to 2026-11-02. CT DEEP's reporting archive runs 2016-07-04 to 2021-12-02.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Hours under advisory per month
MonthHours under advisoryFrom discharge windowsHours in monthCoverage
Jan 202200744
Feb 202200672
Mar 202200744
Apr 202200720
May 202200744
Jun 202200720
Jul 202200744
Aug 202200744
Sep 202200720
Oct 202200744
Nov 202200720
Dec 202200744
Jan 202300744
Feb 202300672
Mar 202300744
Apr 202300720
May 202300744
Jun 202300720
Jul 202300744
Aug 202300744
Sep 202300720
Oct 202300744
Nov 202300720
Dec 202300744
Jan 20245858744
Feb 202400696
Mar 202400744
Apr 202400720
May 202400744
Jun 202400720
Jul 202400744
Aug 202400744
Sep 202400720
Oct 202400744
Nov 202400720
Dec 202400744
Jan 202500744
Feb 202500672
Mar 202500744
Apr 202500720
May 202500744
Jun 202500720
Jul 202500744
Aug 202500744
Sep 202500720
Oct 202500744
Nov 202500720
Dec 202500744
Jan 202600744
Feb 202600672
Mar 202600744
Apr 202600720
May 202600744
Jun 202600720
Jul 202600744
Aug 202600744
Sep 202600720
Oct 202600744
Nov 20260032

Days with a discharge per month

A day counts when any counted discharge was under way on it (start to reported end, local time); an event with no end counts its start day.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports. Covered 2022-01-01 to 2026-11-02.

Show table
Days with a discharge per month
MonthDays with a dischargeCoverage
Jan 20220
Feb 20220
Mar 20220
Apr 20220
May 20220
Jun 20220
Jul 20220
Aug 20220
Sep 20220
Oct 20220
Nov 20220
Dec 20220
Jan 20230
Feb 20230
Mar 20230
Apr 20230
May 20230
Jun 20230
Jul 20230
Aug 20230
Sep 20230
Oct 20230
Nov 20230
Dec 20230
Jan 20241
Feb 20240
Mar 20240
Apr 20240
May 20240
Jun 20240
Jul 20240
Aug 20240
Sep 20240
Oct 20240
Nov 20240
Dec 20240
Jan 20250
Feb 20250
Mar 20250
Apr 20250
May 20250
Jun 20250
Jul 20250
Aug 20250
Sep 20250
Oct 20250
Nov 20250
Dec 20250
Jan 20260
Feb 20260
Mar 20260
Apr 20261
May 20260
Jun 20260
Jul 20260
Aug 20260
Sep 20260
Oct 20260
Nov 20260

Discharge events per year, 2016 to 2026

5 events, 2016 to 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Bypass, blended or other
  • Partly covered or sparse source

CT DEEP dashboard records begin 2021-12-02; where CT DEEP's annual report covers a discharger's month, the annual report is counted instead. CT DEEP annual reports (Sewage Right-to-Know) cover 2021-01-01 to 2026-11-02. CT DEEP's reporting archive runs 2016-07-04 to 2021-12-02.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Discharge events per year, 2016 to 2026
YearCombined sewer overflowSanitary sewer overflowBypass, blended or otherTotalCoverage
20160000Partly covered or sparse source
20170202
20180000
20190000
20200000
20210101Partly covered or sparse source
20220000
20230000
20240011
20250000
20260101

Reported volume per year

Gallons, summed from the 4 events that gave a number (1 did not).

  • Partly covered or sparse source

1 of 5 events gave no volume as a number (1 gave a range); only numbers are summed. CT DEEP's 2016-2021 archive gives volumes as ranges ("20,001 - 50,000 gallons"); they are not summed.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Reported volume per year
YearGallonsEvents with a numberEvents withoutCoverage
2016000Partly covered or sparse source
201720,00020
2018000
2019000
2020000
2021001Partly covered or sparse source
2022000
2023000
2024010
2025000
202666010

Hours under advisory per year

Hours under advisory each year; 2026 to date.

  • Advisory in effect
  • Partly covered or sparse source

1 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Hours under advisory per year
YearHours under advisoryShare of the yearCoverage
201600.0%Partly covered or sparse source
2017490.6%
201800.0%
201900.0%
202000.0%
2021490.6%Partly covered or sparse source
202200.0%
202300.0%
2024580.7%
202500.0%
202600.0%

Share of the May to October season under advisory

Share of the hours from May 1 to October 31 with an advisory in effect.

  • Advisory in effect
  • Season partly covered

Seasons only partly covered by a source: 2016 (share is of the covered hours). 1 discharge events have no reported end and no ongoing status; under the status rules they set caution, not an advisory, and add no hours here.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Share of the May to October season under advisory
SeasonShare under advisoryHours under advisoryHours coveredSeason hoursPartly covered
20160.0%02,8764,416yes
20170.0%04,4164,416
20180.0%04,4164,416
20190.0%04,4164,416
20200.0%04,4164,416
20210.0%04,4164,416
20220.0%04,4164,416
20230.0%04,4164,416
20240.0%04,4164,416
20250.0%04,4164,416
20260.0%04,4164,416

Discharge events by calendar month, all years

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

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

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Discharge events by calendar month, all years
MonthEventsYears of records
Jan110
Feb010
Mar110
Apr110
May010
Jun010
Jul011
Aug011
Sep011
Oct011
Nov011
Dec210

Discharge events by outfall

The 4 outfalls with the most events of 4, all years.

CT DEEP dashboard records begin 2021-12-02; where CT DEEP's annual report covers a discharger's month, the annual report is counted instead. CT DEEP annual reports (Sewage Right-to-Know) cover 2021-01-01 to 2026-11-02. CT DEEP's reporting archive runs 2016-07-04 to 2021-12-02.

Sources: CT DEEP CSO/SSO dashboard; CT DEEP Sewage Right-to-Know annual reports; CT DEEP reporting archive 2016-2021. Covered 2016-07-04 to 2026-11-02.

Show table
Discharge events by outfall
OutfallDischargerEvents
Manhole, intersection coogan blvd greenmanville aveStonington - Mystic2
Treatment Plant, 22 Edgemont St, Stonington, CTSTONINGTON - MYSTIC1
175 Whitehall aveStonington - Mystic1
Manhole, Coogan Blvd, Stonington, CTSTONINGTON - MYSTIC1
How these charts are counted

Discharge events are counted once: where a source publishes both public notices and verified reports (MassDEP, Vermont DEC), a discharger's month with any verified report counts its verified reports only, and other months count notices. Revisions are folded into the record they revise, and EPA copies of a state report are not counted twice. Monthly and yearly totals (Maine DEP, EPA discharge monitoring reports, Portsmouth) are shown on their own and never added to the event counts. Hours under advisory follow the map's red rules. A muted band marks periods no source covers: a gap there is missing data, not a quiet month.

  • CT DEEP CSO/SSO dashboard: 2021-12-02 to now
  • CT DEEP Sewage Right-to-Know annual reports: 2021-01-01 to now
  • CT DEEP reporting archive 2016-2021: 2016-07-04 to 2021-12-02

Every event on Mystic River

Events placed on Mystic River, newest first
StartEnd Discharger OutfallTypeVolumeSourceLinks
Apr 21, 2026, 7:30 AM EDT not reported STONINGTON - MYSTIC Manhole, Coogan Blvd, Stonington, CT Sanitary sewer overflow 660 gal STONINGTON - MYSTIC (CT DEEP Performance Dashboard) via CT DEEP CSO/SSO Performance Dashboard (QScend), record 10582, the source gives no report time, retrieved 2026-11-02 11:20 UTC · notice record below · Map
Full record (older than 180 days, so no page of its own)

This record in the archive list
Jan 13, 2024, 6:00 AM EST Jan 13, 2024, 3:45 PM EST STONINGTON - MYSTIC Treatment Plant, 22 Edgemont St, Stonington, CT Treatment plant bypass 0 gal STONINGTON - MYSTIC (CT DEEP Sewage Right-to-Know annual report 2025) via ct-deep-annual, record x034acc8235ec, published Mar 31, 2025, 1:52 PM EDT, retrieved 2026-11-02 11:53 UTC · notice record below · Map
Full record (older than 180 days, so no page of its own)

This record in the archive list
Mar 26, 2021, 3:18 PM EDT Mar 26, 2021, 4:18 PM EDT Stonington - Mystic 175 Whitehall ave Sanitary sewer overflow “51 - 500 gallons” Stonington - Mystic (CT DEEP reporting archive 2016-2021) via ct-deep-archive, record bypass-35964823, reported Mar 26, 2021, 5:22 PM EDT, retrieved 2026-11-02 11:54 UTC · notice record below · Map
Full record (older than 180 days, so no page of its own)

This record in the archive list
Dec 2, 2017, 9:50 AM EST Dec 2, 2017, 11:00 AM EST Stonington - Mystic Manhole, intersection coogan blvd greenmanville ave Sanitary sewer overflow 10,000 gal Stonington - Mystic (CT DEEP reporting archive 2016-2021) via ct-deep-archive, record bypass-35964480, reported Mar 1, 2018, 10:47 AM EST, retrieved 2026-11-02 11:54 UTC · notice record below · Map
Full record (older than 180 days, so no page of its own)

This record in the archive list
Dec 2, 2017, 9:50 AM EST Dec 2, 2017, 11:00 AM EST Stonington - Mystic Manhole, intersection coogan blvd greenmanville ave Sanitary sewer overflow 10,000 gal Stonington - Mystic (CT DEEP reporting archive 2016-2021) via ct-deep-archive, record bypass-35964479, reported Dec 2, 2017, 10:30 AM EST, retrieved 2026-11-02 11:54 UTC · notice record below · Map
Full record (older than 180 days, so no page of its own)

This record in the archive list

Outfalls on this water

No outfall in the registry is matched to this water.

Launches

Source: OpenBoatLaunch launch records (public agency data and OpenStreetMap, ODbL). · Mystic River on OpenBoatLaunch

Sources covering this water

5 events placed on this water in this build.