Massachusetts / Events /

Combined sewer overflow: CITY OF CHELSEA, Jul 21, 2026

Ended (as reported) · CITY OF CHELSEA (MassDEP sewage notification portal)

Source: CITY OF CHELSEA (MassDEP sewage notification portal) via MassDEP CSO API behind the portal (eeaonline.eea.state.ma.us/dep/CSOAPI/api/), record b4b38171-499b-4300-8007-01b6a8c0874e, published Jul 21, 2026, 6:05 PM EDT, retrieved 2026-11-02 10:58 UTC · notice

1. The reported outfall

Outfall reported by CITY OF CHELSEA (MA0101877 outfall CHE004): “PEARL ST”. Location: 42.38665, -71.03929, from the state's or EPA's outfall layer.

2. Waters named in the notice

The notice names: “MYSTIC RIVER”. We place it on Mystic River, MA. Matched by the name of the water in the source record.

3. Modeled downstream reach

No modeled reach for this record in this build.

Open on the main map

When: three different times

The time of the event, the time the source reported, published or updated it, and the time we fetched it are kept apart. Times are shown in New England time; the record keeps the original offsets.

Started

Jul 21, 2026, 5:45 PM EDT

Ended

not reported

Precision

Known to the minute

Reported to the source

not given

Published

Jul 21, 2026, 6:05 PM EDT

Source last updated

not given

We fetched it

2026-11-02 10:58 UTC

What and how much

Type

Combined sewer overflow

Status in the record

Ended (as reported)

Material

“CSO – UnTreated”

Volume

not reported (not stated whether estimated or measured)

Volume in the source's words

none

Advice

“Avoid contact with these water bodies for 48 hours after the discharge or overflow ceases due to increased health risks from bacteria and other pollutants. See website for more information on whether specific resource areas, such as bathing beaches, are affected.”

Advice window

48 hours

Basis

314 CMR 16.04(10)(g)

What it does to the map, over time

• Caution Mystic River: Discharge record with no status and no reported end, Jul 21, 2026, 5:45 PM EDT to Aug 4, 2026, 6:05 PM EDT
• Unresolved: no end reported Mystic River: Unresolved: no end reported, Aug 4, 2026, 6:05 PM EDT to Aug 20, 2026, 6:05 PM EDT
• No current report Mystic River: Unresolved: no end reported (off the map after 30 days), Aug 20, 2026, 6:05 PM EDT to Oct 19, 2026, 5:45 PM EDT

Source: intervals computed by DirtyWaterWatch (build/status.py) from this record and the rules on the methods page, as of 2026-11-02 11:56 UTC.

Source and revisions

Source

MassDEP CSO API behind the portal (eeaonline.eea.state.ma.us/dep/CSOAPI/api/)

Record id at the source

b4b38171-499b-4300-8007-01b6a8c0874e

Original notice

https://eeaonline.eea.state.ma.us/portal/dep/cso-data-portal/detail…

Revision of

none (first record)

Revised by

no later revision

{
  "incidentId": "b4b38171-499b-4300-8007-01b6a8c0874e",
  "incidentNumber": "26016747",
  "incidentDate": "2026-07-21T00:00:00",
  "incidentTime": "17:45",
  "amPm": null,
  "reporterClass": "Public Notification Report",
  "eventType": "CSO – UnTreated",
  "permiteeClass": "CSO",
  "permiteeName": "CITY OF CHELSEA",
  "permiteeId": "MA0101877",
  "outfallId": "CHE004",
  "municipality": "CHELSEA",
  "reportingType": "Initial-Ceased",
  "location": "PEARL ST",
  "latitude": null,
  "longitude": null,
  "waterBody": "MYSTIC RIVER",
  "waterBodyDescription": null,
  "volumnOfEvent": "",
  "rainfallData": "",
  "hours": "",
  "minutes": "",
  "month": null,
  "year": null,
  "additionalInformation": null,
  "submittedDate": "2026-07-21T18:05:43.11",
  "parentIncidentId": null,
  "_report_class": "Public Notification Report",
  "_tz_assumed": "America/New_York (portal gives local clock time without zone)",
  "_ended_note": "reported ceased; the portal gives no cessation time",
  "_coords": "MassDEP CSOs layer DEP_OUTFL_ CHE004 (locations are estimates)",
  "_water": {
    "via": "crosswalk on portal waterbody",
    "text": "MYSTIC RIVER",
    "confidence": "high"
  },
  "_advice_source": "required wording of 314 CMR 16.04(10)(g); the permittee's own advisory is only in an attachment the portal will not serve"
}