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Washington / Sewer operators /

Seattle Public Utilities (combined sewer system)

Sewer utility with combined sewers · Washington · Seattle

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.

Solid dots mark combined sewer outfalls. Small hollow diamonds mark places named in its overflow reports (provisional). Grey dots are closed outfalls. Dashed river stretches are estimates of where a discharge travels. Square boat markers mark boat launches listed by OpenBoatLaunch.

Federal wastewater discharge permit (NPDES)
WA0031682
Wastewater outlets
88 combined sewer outfalls listed by EPA or state agencies; 3 places named in its own overflow reports (provisional locations) (the state's combined sewer records list 86) · List
Waters listed as receiving wastewater
Lake Washington; Lake Union; Salmon Bay; Elliott Bay; Duwamish Waterway; Puget Sound
Tracked waters
Andrews Bay, WA, Duwamish River, WA, Duwamish Waterway, WA, East Waterway, WA, Elliott Bay, WA, Lake Union, WA, Lake Washington Ship Canal, WA, Lake Washington, WA, Portage Bay, WA, Puget Sound, WA, Salmon Bay Waterway, WA, Shilshole Bay, WA
Discharge records counted
17 records · latest
Total reported volume in these records
59,022 gallons across the 13 records that give a volume (4 without one)

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 2026-11-06 06:13 UTC.

Public notices and alerts

Pages where Seattle Public Utilities (combined sewer system) or the state publishes its notices (check them for an alert sign-up):

Its public-notice channels

Source: Seattle Public Utilities (combined sewer system)'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

Rain and discharges

The NOAA MRMS radar-only rainfall estimate for the 24 hours to the latest hour, read every hour at each outfall from the radar grid. We show a caution when the rain reaches the amount below and no discharge report has arrived.

Threshold
0.1 in of rain in 24 hours (site default: This site's default: 0.1 inch of rain in 24 hours at a combined sewer outfall, applied where the state publishes no rain trigger of its own)
Radar now
1.7 in in the 24 hours to Nov 6, 2026, 12:00 AM EST
Forecast
Rain expected: 0.17 in forecast in the next 24 hours (NWS forecast issued Nov 5, 2026, 1:26 PM EST); discharges here have begun at 0.1 in.
Status
A discharge notice from the operator sets the status instead

Source: NOAA National Weather Service, MRMS radar-only rainfall estimate, valid Nov 6, 2026, 12:00 AM EST, retrieved 2026-11-06 06:09 UTC; threshold: site default; rule: How it works, discharge likely or possible.

Wastewater outlets

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

88 combined sewer outfalls listed by EPA or state agencies; 3 places named in its own overflow reports (provisional locations).

Combined sewer outfalls

88 outfalls · 1 closed

Showing 12 of 88.

Source: U.S. Environmental Protection Agency (EPA) national combined sewer outfall inventory (ECHO) and state outfall layers. Open or closed as EPA's inventory lists it. DirtyWaterWatch links outlets to waters using permit numbers, locations and names.

Places named in overflow reports (provisional)

3 places · 3 not on the map (reports say the sewage reached no water)

Provisional location from overflow reports. Where the operator's own reports put an overflow: a manhole, pump station or plant. Not an outfall listed in a permit.

  • Reported place · 1 overflow report, latest Oct 7, 2026 · confidence medium · no water record yet · not on the map: its reports say the sewage did not reach a water
  • Reported place · 1 overflow report, latest Aug 30, 2026 · confidence medium · no water record yet · not on the map: its reports say the sewage did not reach a water
  • Reported place · 1 overflow report, latest Jun 24, 2026 · confidence medium · no water record yet · not on the map: its reports say the sewage did not reach a water

Source: the operator's own overflow reports to the state. DirtyWaterWatch groups reports within 50 metres into one place and finds the water below it with U.S. Geological Survey river maps (NLDI, NHDPlus). Not a permitted outfall; provisional until an official outfall record exists.

Reports and advisories

Combined sewer overflow (CSO): sewage mixed with rainwater spills from a shared sewer system. Sanitary sewer overflow (SSO): sewage spills from a sewer meant to carry sewage separately from rainwater.

Reports linked to Seattle Public Utilities (combined sewer system), newest first
WhenReportStatus
to Nov 5, 4:10 PMLake Union · 145 Seattle CSO outfall 145 · CSO · volume not reported report · notice · mapto Nov 7, 4:10 PM
to Nov 5, 10:10 AMLake Union · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 7, 10:10 AM
to Nov 4, 10:30 AMLake Union · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 6, 10:30 AM
Water not mapped · 6000 Block of 44th Avenue NW, Seattle · SSO · 29,922 gallons report · noticereported
to 9:18 PMDuwamish Waterway · 1100 Block of 23rd Ave S, Seattle · SSO · 15 gallons report · notice · mapended
Water not mapped · 1000 Block of NE 133rd St, Seattle · SSO · 750 gallons report · noticereported
to Sep 27, 2:22 AMLake Washington · 8700 Block of Sandpoint Way NE, Seattle · SSO · 18,100 gallons report · notice · mapended
to 8:40 PMLake Union · Eastlake Ave E and Roanoke St, Seattle · SSO · 4,000 gallons report · notice · mapended
to 10:10 PMWater not mapped · 5th Avenue and Columbia Street, Seattle · SSO · 120 gallons report · noticeended
Water not mapped · 1800 Block of NE 96th St, Seattle · SSO · 1 gallon report · noticereported
Water not mapped · 1200 Block of 19th Avenue East, Seattle · SSO · 2,244 gallons report · noticereported
Water not mapped · 800 Block of 5th Avenue, Seattle · SSO · 1,000 gallons report · noticereported
to 11:20 PMWater not mapped · 800 Block of 5th Avenue, Seattle · SSO · 650 gallons report · noticeended
Water not mapped · 4-Thousand Block of NE 92nd Street, Seattle · SSO · volume not reported report · noticereported
to Jul 16, 2:00 PMWater not mapped · 4100 Block of Roosevelt Way NE, Seattle, WA · SSO · 1,200 gallons report · noticeended
to Jul 7, 3:01 AMWater not mapped · Washington Park Arboretum · SSO · 1,000 gallons report · noticeended
to 1:30 PMWater not mapped · 2800 Block of S Byron St, Seattle, WA · SSO · 20 gallons report · noticeended

Sources: King County / Seattle CSO overflow status CSV, retrieved 2026-11-05 21:17 UTC; Washington Ecology Sewage Spills list (RCW 90.48.636 public website), retrieved 2026-11-06 06:01 UTC. A report's record id and times show when you hover or focus its "report" link.

Download these reports as CSV

All reports in Washington by year: 2026 (17 from Seattle Public Utilities (combined sewer system))

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: a status resting on a source that could not be checked on schedule.
  • Discharge or advisory reported: to the latest update
    3 reports: Lake Union 3
    Show records

    The records are also in the report table on this page.

  • Caution: to
    1 report: Duwamish Waterway 1
    Show records

    The records are also in the report table on this page.

  • Discharge or advisory reported: to
    1 report: Duwamish Waterway 1
    Show records

    The records are also in the report table on this page.

  • Caution: to
    2 reports: Lake Union 1, Lake Washington 1
    Show records

    The records are also in the report table on this page.

  • Discharge or advisory reported: to
    1 report: Lake Washington 1
    Show records

    The records are also in the report table on this page.

  • Caution: to
    1 report: Lake Union 1
    Show records

    The records are also in the report table on this page.

  • Discharge or advisory reported: to
    1 report: Lake Union 1
    Show records

    The records are also in the report table on this page.

Source: DirtyWaterWatch calculations using the reports named above and the published status rules. Updated 2026-11-06 06:13 UTC.

Reported discharges over time

  • Discharges reported by Seattle Public Utilities (combined sewer system), last 12 months17December 2025 to November 2026Verified reports where available, else notices; revisions and duplicates counted once.
  • Days with a discharge reported by Seattle Public Utilities (combined sewer system), last 12 months18December 2025 to November 2026A day counts once however many discharges were under way on it.
  • Hours with a discharge or advisory status from Seattle Public Utilities (combined sewer system)'s reports, last 12 months68December 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 (Seattle Public Utilities (combined sewer system))0.9%May to October 2026; incomplete source coverageShare of May 1 to October 31 hours with red status by the map's rules, of the hours a source covered.

Treatment bypass: wastewater skips one or more treatment steps. Blended discharge: wastewater that skipped some treatment is mixed with treated wastewater.

Reported discharges per month

17 reported discharges, January 2022 to November 2026.

  • Combined sewer overflow
  • Sanitary sewer overflow
  • Treatment bypass, blended or other
  • No tracked source for this period
  • Incomplete source coverage
No tracked source

No tracked source covers January 2022 to May 2026.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

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
  • No tracked source for this period
  • Incomplete source coverage
No tracked source

No tracked source covers January 2022 to May 2026. 7 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.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

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.

  • No tracked source for this period
  • Incomplete source coverage
No tracked source

No tracked source covers January 2022 to May 2026.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

Reported volume per year

Gallons (axis: K thousand, M million), summed from the 13 reports that gave a volume as a number (4 did not).

  • Incomplete source coverage
Limited records

4 of 17 discharge reports gave no volume as a number; only numbers are summed.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

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
  • Incomplete source coverage
Limited records

7 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.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

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
  • Season with incomplete source coverage

Seasons with incomplete source coverage: 2026. The share is of the hours a source covered. 7 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.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

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.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table

Reported discharges by wastewater outlet

Wastewater outlets with the most tracked discharge records: 10 of 15, all years. Counts depend on reporting coverage and do not measure legal compliance or harm.

Sources: wa-ecology-sewage-spills; wa-kc-cso-status-csv. Records cover June 15, 2026 to November 6, 2026.

Show table
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.

  • wa-ecology-sewage-spills: records from June 15, 2026 to the latest update
  • wa-kc-cso-status-csv: records from November 4, 2026 to the latest update