Illinois Great Lakes waterbody · state assessment record
Lake Michigan Nearshore
Assessment decisions reported by Illinois to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle, a cycle that is open for public comment.
- 196
- Assessed square miles
- Great Lakes Open Water
- Water type
This waterbody in one line
Lake Michigan Nearshore, a Great Lakes waterbody in Illinois, is assessed as not supporting one or more designated uses, with 9 listed impairment causes in the state's most recent Integrated Report cycle (2026), a cycle that is open for public comment. By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (9 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
- P100
- Assessed size nationally
- P0
- 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.
Lake Michigan Nearshore 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 Lake Michigan Nearshore nationally is assessed size: 125,440 acres, larger than 100% of the 38,628 lake-type units with an area on file.
Longer than most cause lists
9 listed causes puts this unit above 100% 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.
Not one verdict, several
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.
Lake Michigan Nearshore: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Lake Michigan Nearshore. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Overall status: not supporting
The filer's overall status for Lake Michigan Nearshore 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 Lake Michigan Nearshore 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 2021, as Illinois filed it. Illinois filed its own confidence on the 5 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 | Not 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 |
| Public and Food Processing Water Supply | Drinking-water supply designation | Fully Supporting Filer confidence: Good |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this Great Lakes waterbody, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Toxaphene | Fish Consumption | 2022 | TMDL priority: Medium |
| Phosphorus, Total | Aesthetic Quality | 2024 | TMDL priority: Medium |
| Aldrin | Fish Consumption | 2026 | TMDL priority: Medium |
| Dieldrin | Fish Consumption | 2026 | TMDL priority: Medium |
| Endrin | Fish Consumption | 2026 | TMDL priority: Medium |
| Heptachlor | Fish Consumption | 2026 | TMDL priority: Medium |
| Mercury | Fish Consumption | 2026 | TMDL approved |
| Mirex | Fish Consumption | 2026 | TMDL priority: Medium |
| Polychlorinated Biphenyls (PCBs) | Fish Consumption | 2026 | TMDL approved |
Reading the record
How current is Lake Michigan Nearshore's evidence?
5 years between the 2026 reporting cycle and monitoring through 2021
Monitoring behind at least one of these designated-use verdicts ran through 2021, as Illinois filed it.
The cycle is when the state reported; the monitoring year, where filed, is when it measured. How to read assessment currency.
Scale and rank
Lake Michigan Nearshore 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 196 square miles (125,440 acres) it ranks 23rd 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 22 lakes with a larger one.
In context
Where Lake Michigan Nearshore 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
196 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
9 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 Lake Michigan Nearshore. 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, Lake Michigan Nearshore ranks 6th by listed-cause count (9 listed causes) and 1st by assessed size among the 388 with an area filed; it sits in the not-supporting set (434 statewide) . Its listed causes include Phosphorus, Total; Mercury; and Polychlorinated Biphenyls (PCBs), which also appear among Illinois's most-filed impairment causes (led by Phosphorus, Total). It also lists Toxaphene, Aldrin, Dieldrin, Endrin, Heptachlor, and Mirex, outside that top-five list.
| Other large assessed lakes in Illinois | Assessed acres |
|---|---|
| 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 |
| Springfield Not Supporting | 4,000 |
Peers near Lake Michigan Nearshore's size or cause load
Similar assessed acres
Nearest filed extents (125,440 acres here).
- Lake Tahoe · 122,902 acres · NV
- Mille Lacs · 128,076 acres · MN
- St. Marys River · 129,983 acres · MI
- Red (Upper Red) · 119,279 acres · MN
Similar cause load
Nearest listed-cause counts (9 here). Peers already in the acreage column are omitted.
- Brownlee Reservoir, Lower (Porters Flat to Brownlee Dam) · 9 causes · ID
- Eagle Lake (Lassen County) · 9 causes · CA
- Gay Stamp Sands Area of Impact · 9 causes · MI
- Goose, Upper Lake · 9 causes · WA
What to do with this record
- The fish-consumption use is assessed as not supporting. Before eating fish from this Great Lakes waterbody, 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_QLM-01. 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.