Washington reservoir · state assessment record
Lake Union (9.85 acres)
Assessment decisions reported by Washington to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 9.85
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Lake Union, a reservoir in Washington, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2022). By assessed acreage it sits among the smaller assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P19
- Assessed size nationally
- P10
- Shorter cause list
- Not Supporting
- aquatic life
Assessment verdicts are the state agency's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
A composite of this record's EPA ATTAINS designated-use verdicts, filed impairment count, and assessment currency, weighted and benchmarked against the national corpus of assessed active waterbodies. This is a water-quality standing, not a human-recreation or property-value judgment, and dimensions with no filed verdict drop out rather than count against the score.
How Lake Union reads against the filed register
Paragraphs are selected by this unit's percentiles and use matrix: different lakes lead with different dimensions. Figures are ATTAINS / portal register arithmetic, not advice.
The signature stat: assessed size
What stands out first is how small the assessed unit is: 9.9 acres, smaller than 81% of the 38,628 lake-type units carrying an area.
Every filed use falls short
On the uses this filer ruled on, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Lake Union: Category 4B reading
Category 4B says other pollution-control requirements are expected to resolve the impairment on Lake Union without a TMDL. The decisive documents are those control requirements, not a load allocation.
Longer than most cause lists
2 listed causes puts this unit above 80% of assessed lake-type records by list length. Treat that as a coding-and-sampling signal: states that split pollutants finely mint longer lists without proving worse water.
Overall status: not supporting
The filer's overall status for Lake Union is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
According to the U.S. Environmental Protection Agency's ATTAINS program, Washington carries 832 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Lake Union without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle.
| Designated use | Group | Verdict |
|---|---|---|
| Aquatic Life - Benthic Sediment | Aquatic-life or related | Not Supporting |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| High Molecular Weight Polycyclic Aromatic Hydrocarbons (Hmw PAHs) in Sediment | Aquatic Life - Benthic Sediment | 2018 | Action recorded (type not published) |
| Low Molecular Weight Polycyclic Aromatic Hydrocarbons (Lmw PAHs) in Sediment | Aquatic Life - Benthic Sediment | 2018 | Action recorded (type not published) |
Reading the record
Lake Union: Category 4B reading
4B Category 4B: impaired, other controls in place (not a TMDL path)
Washington filed this assessment unit as Category 4B: impaired, with other controls in place rather than a pollutant-budget TMDL under 303(d).
Scale and rank
Lake Union is one of 832 lake-type waterbodies reported to EPA from Washington, and one of 385 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 9.85 assessed acres it ranks 31,487th by assessed size among the 38,628 lakes the dataset carries an area for, counting a state’s repeated filings of one water once, behind 31,486 lakes with a larger one.
Awaiting a filing
The state has not yet filed a definitive fish-consumption verdict and a definitive recreation verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where Lake Union sits nationally
Assessed size among U.S. lakes
Distribution of assessed acreage across ATTAINS lakes filed with an area, counting a state’s repeated filings of one water once
10 Top 81% larger than 19% of 38,628 lakes
lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
Listed causes vs waterbodies carrying a verdict
How many impairment causes U.S. waterbodies with a reported verdict carry
2 Longer than most more listed causes than 80% of 23,610 waterbodies carrying a verdict
named waterbodies carrying a verdict, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark Lake Union. Hover or tap any bar for its full count and share.
In context
Washington context
ATTAINS carries 832 lake-type waterbodies in Washington, 393 assessed as not supporting at least one use and 0 fully supporting. Among the 385 indexed units there, Lake Union ranks 134th by listed-cause count (2 listed causes) and 362nd by assessed size among the 385 with an area filed; it sits in the not-supporting set (393 statewide) . Its listed causes (High Molecular Weight Polycyclic Aromatic Hydrocarbons (Hmw PAHs) in Sediment and Low Molecular Weight Polycyclic Aromatic Hydrocarbons (Lmw PAHs) in Sediment) sit outside Washington's top-five list, which is led by Non-Native Aquatic Plants.
| Other large assessed lakes in Washington | Assessed acres |
|---|---|
| Bumping Lake Not Assessed | 1,354 |
| Sullivan Lake Not Supporting | 1,298 |
| Deer Lake Not Supporting | 1,146 |
| Loon Lake Not Supporting | 1,094 |
| American Lake Not Supporting | 1,092 |
| Newman Lake Not Supporting | 1,091 |
Peers near Lake Union's size or cause load
Similar assessed acres
Nearest filed extents (9.85 acres here).
- Pout Pond · 9.85 acres · NH
- Bright Lake · 9.85 acres · WI
- Sawmill Lake · 9.85 acres · WI
- South Fork Dam No. 1 · 9.85 acres · WV
Similar cause load
Nearest listed-cause counts (2 here). Peers already in the acreage column are omitted.
- 12th St. Beach · 2 causes · IL
- 31st St. Beach · 2 causes · IL
- 49th St. Beach · 2 causes · IL
- 57th St. Beach · 2 causes · IL
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. Consumption status guide
- Impairment listings follow the Clean Water Act 303(d) process; a listing is a regulatory finding, not a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
Assessment decisions on this page are rendered directly from state Integrated Report records in EPA's ATTAINS system; gauge figures are daily-value observations from the USGS National Water Information System, no number is typed in by an editor. Overall status, use verdicts, and causes are the state's reported decisions for assessment unit WA47122G3E3_NE. Counts and percentiles are computed across all lake-type records PlainLakes ingests from ATTAINS. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.