Is Lake Union Polluted?
Yes — Lake Union in King County, Washington is on the EPA's Clean Water Act 303(d) impaired-waters list (2018 assessment cycle). It is cited for Toxic inorganics. "Impaired" is a legal designation, separate from the lake's EPA condition class water-quality readings: it means at least one designated use (such as swimming, aquatic life, or fish consumption) does not meet state standards for the listed pollutant.
EPA 303(d) Listing
| On 303(d) impaired list | Listed impaired |
| Cleanup plan (TMDL) | Not yet written |
| Assessment cycle | 2018 |
| EPA IR category | 4B |
| Uses not supported | Aquatic life |
| EPA names this lake in the listing | Yes |
| Location | King County, Washington |
Pollutants Cited
- Toxic inorganics — listed by EPA as exceeding water-quality standards for at least one designated use.
Specific parameters in the EPA record: High Molecular Weight Polycyclic Aromatic Hydrocarbons (Hmw PAHs) in Sediment, Low Molecular Weight Polycyclic Aromatic Hydrocarbons (Lmw PAHs) in Sediment.
What this means for using Lake Union
Review the EPA assessment and any state advisories before relying on Lake Union for swimming, fishing, or other uses. An impairment listing does not mean the lake is closed — most impaired lakes remain open for boating and swimming. It means a specific pollutant exceeds a standard for a specific use. See the full breakdown on the lake report. The official EPA assessment is available in the ATTAINS waterbody report.
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