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Washington / Waters /

Lake Union

Lake in Washington, near Seattle

Current status

Discharge or advisory reported

A discharge is reported as ongoing, a post-discharge period applies, or an official advisory is listed. Open the report for its source, dates and advice. This status since . Why this status, and its source

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. A yellow ring with a dashed edge means discharge likely or possible: heavy rain, no report received. Square boat markers mark boat launches listed by OpenBoatLaunch.

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. A forecast, not a report.

Check King County Wastewater Treatment Division (West Point, South, Brightwater, Vashon and Carnation plants and King County's CSOs)'s notices · Bookmark this water page and check it before each trip · Report a missing notice or error

About this status

Discharge or advisory reported: discharge reported; shown for 48 hours after the reported end (the notice's own period). 3.1 in of rain fell in the 24 hours to Nov 6, 2026, 12:00 AM EST at King County Wastewater Treatment Division (West Point, South, Brightwater, Vashon and Carnation plants and King County's CSOs)'s outfalls (NOAA radar estimate).

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. · Updated

Reports behind this status

Combined sewer overflow (CSO): sewage mixed with rainwater spills from a shared sewer system.

Reports behind the status of Lake Union, newest first
WhenReportStatus
to Nov 5, 4:10 PMSeattle Public Utilities · 145 Seattle CSO outfall 145 · CSO · volume not reported report · notice · mapto Nov 7, 4:10 PM
to Nov 5, 10:10 AMSeattle Public Utilities · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 7, 10:10 AM
to Nov 4, 10:30 AMSeattle Public Utilities · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 6, 10:30 AM

Sources: King County / Seattle CSO overflow status CSV, retrieved 2026-11-05 21:17 UTC. A report's record id and times show when you hover or focus its "report" link.

Advice in the reports

King County Wastewater Treatment Division and Seattle Public Utilities (CSO status map) · Nov 5, 2026 · Current status: sets this water's status now

“Stay out of the water near combined sewer overflow outfalls for 48 hours after a combined sewer overflow occurs.”

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: Seattle Public Utilities 3
    Show records

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

  • Caution: to
    1 report: Seattle Public Utilities 1
    Show records

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

  • Discharge or advisory reported: to
    1 report: Seattle Public Utilities 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 affecting Lake Union in Washington, last 12 months44 affecting this lake: 4 reported on Lake Union; none arriving from upstreamDecember 2025 to November 2026Verified reports where available, else notices; revisions and duplicates counted once. Arriving discharges are estimated from modeled downstream reaches.
  • Days with a discharge affecting Lake Union in Washington, last 12 months3Reported on Lake Union in Washington: 3 · Arriving from outfalls upstream, estimated: 0 (counted apart; together they need not equal the total)December 2025 to November 2026A day counts once however many discharges were under way on it.
  • Hours with a discharge or advisory status on Lake Union in Washington, last 12 months40Reported on Lake Union in Washington: 40 · Arriving from outfalls upstream, estimated: 0December 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 on Lake Union in Washington0.0%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.
  • Records behind the last-90-days strip for Lake Union in Washington4Reported on Lake Union in Washington: 4 · Arriving from outfalls upstream, estimated: 0last 90 daysEvery distinct record the strip lists for its red, yellow and unresolved hours, notices and unresolved reports included; counted as the strip counts them.

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. Blended discharge: wastewater that skipped some treatment is mixed with treated wastewater. Outfall: a pipe or outlet where wastewater enters a water body.

Reported discharges per month

4 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
Limited records

No tracked source covers January 2022 to April 2022.

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 this water had a discharge or advisory status under DirtyWaterWatch rules.

  • Discharge or advisory reported
  • No tracked source for this period
  • Incomplete source coverage
Limited records

No tracked source covers January 2022 to April 2022.

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
Limited records

No tracked source covers January 2022 to April 2022.

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 1 report that gave a volume as a number (3 did not).

  • Incomplete source coverage
Limited records

3 of 4 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

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.

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: 3 of 3, 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.

  • U.S. Environmental Protection Agency sewer overflow records: records from May 3, 2022 to the latest update (limited records)
  • 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

Reports linked to Lake Union

Reports linked to Lake Union, newest first
WhenReportStatus
to Nov 5, 4:10 PMSeattle Public Utilities · 145 Seattle CSO outfall 145 · CSO · volume not reported report · notice · mapto Nov 7, 4:10 PM
to Nov 5, 10:10 AMSeattle Public Utilities · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 7, 10:10 AM
to Nov 4, 10:30 AMSeattle Public Utilities · 124 Seattle CSO outfall 124 · CSO · volume not reported report · notice · mapto Nov 6, 10:30 AM
to 8:40 PMSeattle Public Utilities · Eastlake Ave E and Roanoke St, Seattle · SSO · 4,000 gallons report · notice · mapended

Sources: Washington Ecology Sewage Spills list (RCW 90.48.636 public website), retrieved 2026-11-06 06:01 UTC.

Download these reports as CSV

All reports in Washington by year: 2026 (4 here)

Wastewater outlets on this water

Combined sewer outfalls

16 outfalls · discharge possible now at 1

Discharge possible: heavy rain, no report received at 1 outfall now: radar rainfall has reached the operator's threshold and no discharge report has arrived (NOAA radar estimate).

Showing 12 of 16.

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.

Sewer operators listed for this water: King County Wastewater Treatment Division (West Point, South, Brightwater, Vashon and Carnation plants and King County's CSOs), Seattle Public Utilities (combined sewer system).

Boat launches

Source: OpenBoatLaunch launch records (public agency data and OpenStreetMap, Open Database License). · Lake Union on OpenBoatLaunch

Nearby waters

Sources covering this water

4 records linked to this water. Updated .