Oklahoma lake · tribal assessment record
Grand Lake Site 15
Assessment decisions reported by Seneca-Cayuga Nation to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2017 reporting cycle.
- 46,500
- Assessed acres
- Lake
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Grand Lake Site 15, a lake in Oklahoma, is assessed as fully supporting its designated uses, with no impairment causes listed in the Seneca-Cayuga Nation's most recent Integrated Report cycle (2017). By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is shorter than on half of assessed lakes (0 listed causes). Aquatic life is assessed as fully supporting.
- Fully Supporting
- overall status
- P100
- Assessed size nationally
- P51
- Shorter cause list
- Fully Supporting
- aquatic life
Assessment verdicts are the Seneca-Cayuga Nation'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.
Grand Lake Site 15 against the ATTAINS 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
The number that most separates Grand Lake Site 15 nationally is assessed size: 46,500 acres, larger than 100% of the 38,628 lake-type units with an area on file.
Shorter than most cause lists
Only 0 causes on file, shorter than 51% of assessed lake-type units. Pair the short list with the use matrix: a single Not Supporting use can still be the whole story.
Every ruled-on use is fully supporting
The filed use determinations for recreation, aquatic life are all Fully Supporting. Where an overall IR category still flags the unit, look at the cause list and report standing rather than treating the use row as empty.
Overall status: fully supporting
Overall status is Fully Supporting. If an IR category or cause row still appears, it usually reflects a prior listing path or a use the overall rollup does not collapse, read those sections rather than stopping at the tile.
According to the U.S. Environmental Protection Agency's ATTAINS program, Oklahoma carries 456 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Grand Lake Site 15 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 Seneca-Cayuga Nation's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle. the Seneca-Cayuga Nation filed 2017 as the year this waterbody was last monitored.
| Designated use | Group | Verdict |
|---|---|---|
| Primary Body Contact Recreation | Recreation | Fully Supporting |
| Warm Water Aquatic Community | Aquatic-life or related | Fully Supporting |
The record
Listed impairment causes
The Seneca-Cayuga Nation's reported assessment lists no impairment causes for this lake.
Reading the record
Where Grand Lake Site 15 sits among peers
8 of 14 Oklahoma lakes assessed this deeply were also judged fully supported
The Seneca-Cayuga Nation ruled definitively on 2 designated uses at Grand Lake Site 15 and found every one of them supported. The dataset shows 14 Oklahoma lakes judged to that same depth.
Oklahoma's assessed lakes are most often judged on 5 or more uses; this one was judged on 2.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 13 | 8 (this record) | 7 | 8 | 9 |
| Mixed | Not possible | 6 | 12 | 30 | 92 |
| None supported | 13 | 0 | 0 | 0 | 0 |
Ringed cell: Grand Lake Site 15. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Grand Lake Site 15 is one of 456 lake-type waterbodies reported to EPA from Oklahoma, and one of 173 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 46,500 assessed acres it ranks 63rd 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 62 lakes with a larger one.
What this record holds
The Seneca-Cayuga Nation completed an assessment here and listed no impairment cause, so the record holds a verdict and its supporting use rows but no pollutant to track over time. The Seneca-Cayuga Nation has not yet filed a definitive fish-consumption verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
Reported trophic class
Eutrophic is the trophic class the filing agency reported to EPA ATTAINS for this assessment unit. It describes nutrient enrichment, not whether the water is safe, and it is not a PlainLakes inference. What the trophic scale measures.
In context
Where Grand Lake Site 15 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
46,500 Top 1% larger than 99%+ 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
0 Among the shortest cause lists fewer listed causes than 51% 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 Grand Lake Site 15. Hover or tap any bar for its full count and share.
In context
Oklahoma context
ATTAINS carries 456 lake-type waterbodies in Oklahoma, 153 assessed as not supporting at least one use and 45 fully supporting. Among the 173 indexed units there, Grand Lake Site 15 ranks 155th by listed-cause count (no listed causes) and 4th by assessed size among the 170 with an area filed; it is one of the 45 fully-supporting indexed records in the state .
| Other large assessed lakes in Oklahoma | Assessed acres |
|---|---|
| Grand Lake Site 12 Not Supporting | 46,500 |
| Grand Lake Site 13 Not Supporting | 46,500 |
| Grand Lake Site 14 Fully Supporting | 46,500 |
| Robert S. Kerr Lake Not Supporting | 43,380 |
| Texoma Lake, Red River Arm, Lower Not Supporting | 31,081 |
| Oologah Lake Not Supporting | 29,460 |
Peers near Grand Lake Site 15's size or cause load
Similar assessed acres
Nearest filed extents (46,500 acres here).
- Rainy · 45,734 acres · MN
- Sebago Lake · 45,624 acres · ME
- Mono Lake · 45,299 acres · CA
- Grand Lake · 47,869 acres · LA
Similar cause load
Nearest listed-cause counts (0 here). Peers already in the acreage column are omitted.
- 31st Street Harbor · 0 causes · IL
- 42nd Avenue East Beach · 0 causes · MN
- 59th Street Harbor · 0 causes · IL
- 657 Dunleavy (Beach) · 0 causes · MI
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 Seneca-Cayuga Nation's reported decisions for assessment unit GL15. 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.