Illinois lake · state assessment record
Cedar (Lake)
Assessment decisions reported by Illinois to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 302
- Assessed acres
- Lake, Freshwater
- Water type
- Mesotrophic
- Reported trophic class
This waterbody in one line
Cedar (Lake), a lake in Illinois, is assessed as not supporting one or more designated uses, with 7 listed impairment causes in the state's most recent Integrated Report cycle (2022). By assessed acreage it sits in the upper quartile by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (7 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as fully supporting. Fish consumption is assessed as not supporting.
- Not Supporting
- overall status
- P86
- Assessed size nationally
- P1
- Shorter cause list
- Fully 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 Cedar (Lake) 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: cause-list length
The standout filed fact is cause-list length: 7 listed impairment causes, a longer list than 99% of assessed lake-type units (n=23,610). List length tracks how states sample and code, not a severity score.
Mixed use determinations
This record splits: Not Supporting on fish consumption, Fully Supporting on recreation, aquatic life. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Cedar (Lake): Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Cedar (Lake). Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Large assessed unit
At 302 acres, Cedar (Lake) clears the upper tercile of assessed lake-type units with an area on file (5,329 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
Overall status: not supporting
The filer's overall status for Cedar (Lake) 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, Illinois carries 783 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Cedar (Lake) 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. Monitoring behind at least one of these designated-use verdicts ran through 2019, as Illinois filed it. Illinois filed its own confidence on the 4 definitive verdicts it rated: Good. That rating is the filer's, in EPA's own field, and EPA publishes no definition of the four words it offers.
| Designated use | Group | Verdict |
|---|---|---|
| Aesthetic Quality | Other | Fully Supporting Filer confidence: Good |
| Aquatic Life | Aquatic-life or related | Fully Supporting Filer confidence: Good |
| Fish Consumption | Fish-consumption or fishery | Not Supporting Filer confidence: Good |
| Primary Contact | Recreation | Fully Supporting Filer confidence: Good |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this lake, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Mercury | Fish Consumption | 2010 | TMDL priority: Medium |
| Aldrin | Fish Consumption | 2022 | TMDL priority: Medium |
| Dieldrin | Fish Consumption | 2022 | TMDL priority: Medium |
| Endrin | Fish Consumption | 2022 | TMDL priority: Medium |
| Heptachlor | Fish Consumption | 2022 | TMDL priority: Medium |
| Mirex | Fish Consumption | 2022 | TMDL priority: Medium |
| Toxaphene | Fish Consumption | 2022 | TMDL priority: Medium |
Reading the record
Where Cedar (Lake) sits among peers
94% of Illinois's lakes assessed this deeply also came out mixed (the standard result at this depth, not a distinction)
Illinois ruled definitively on 4 designated uses at Cedar (Lake) and found 1 of 4 not supported. The dataset shows 47 Illinois lakes judged to that same depth.
Illinois's assessed lakes are most often judged on 2 uses; this one was judged on 4.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 8 | 43 | 12 | 0 | 0 |
| Mixed | Not possible | 192 | 107 | 44 (this record) | 1 |
| None supported | 27 | 54 | 6 | 3 | 0 |
Ringed cell: Cedar (Lake). Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Cedar (Lake) is one of 783 lake-type waterbodies reported to EPA from Illinois, and one of 439 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 302 assessed acres it ranks 5,330th 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 5,329 lakes with a larger one.
Reported trophic class
Mesotrophic 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 Cedar (Lake) 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
302 Top 14% larger than 86% 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
7 Longer than most more listed causes than 99% 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 Cedar (Lake). Hover or tap any bar for its full count and share.
In context
Illinois context
ATTAINS carries 783 lake-type waterbodies in Illinois, 434 assessed as not supporting at least one use and 63 fully supporting. Among the 439 indexed units there, Cedar (Lake) ranks 22nd by listed-cause count (7 listed causes) and 69th by assessed size among the 388 with an area filed; it sits in the not-supporting set (434 statewide) . Its listed causes include Mercury, which also appears among Illinois's most-filed impairment causes (led by Phosphorus, Total). It also lists Aldrin, Dieldrin, Endrin, Heptachlor, Mirex, and Toxaphene, outside that top-five list.
| Other large assessed lakes in Illinois | Assessed acres |
|---|---|
| Lake Michigan Nearshore Not Supporting | 125,440 |
| Carlyle Not Supporting | 24,580 |
| Rend Not Supporting | 18,900 |
| Shelbyville Not Supporting | 11,000 |
| Crab Orchard Not Supporting | 6,965 |
| Clinton Not Supporting | 4,895 |
Peers near Cedar (Lake)'s size or cause load
Similar assessed acres
Nearest filed extents (302 acres here).
- Maysville Lake (Wiley Post) · 302 acres · OK
- Bass · 302 acres · MN
- Adney · 302 acres · MN
- Sunset · 302 acres · MN
Similar cause load
Nearest listed-cause counts (7 here). Peers already in the acreage column are omitted.
- Adder Pond · 7 causes · NH
- Arrow Lake · 7 causes · TN
- Barton Cove · 7 causes · MA
- Blue Heron Lagoon · 7 causes · MI
What to do with this record
- The fish-consumption use is assessed as not supporting. Before eating fish from this lake, check your state fish-advisory program for species-specific meal limits. 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 IL_RTK. 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.