Illinois lake · state assessment record
Hennepin-Hopper
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.
- 1,245
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Hennepin-Hopper, a lake in Illinois, is assessed as not supporting one or more designated uses, with 2 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 5% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Fish consumption is assessed as not supporting.
- Not Supporting
- overall status
- P95
- Assessed size nationally
- P10
- Shorter cause list
- Not Supporting
- fish consumption
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.
Reading Hennepin-Hopper's filed record
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: monitoring lag
The signature tension is currency: the reporting cycle is 2026 while monitoring evidence runs through 2015, a 11-year gap. Cycle year and last-monitored year move independently in ATTAINS; this page shows both.
Large assessed unit
At 1,245 acres, Hennepin-Hopper clears the upper tercile of assessed lake-type units with an area on file (1,946 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
Every ruled-on use is not supporting
On the uses this filer ruled on, fish consumption, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Hennepin-Hopper: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Hennepin-Hopper. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Large within Illinois
Among Illinois's 388 indexed units with an area, Hennepin-Hopper ranks 28 by assessed size, toward the large end of that state file.
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 Hennepin-Hopper 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 2015, as Illinois filed it. Illinois filed its own confidence on the one definitive verdict 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 |
|---|---|---|
| Fish Consumption | Fish-consumption or fishery | Not 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 |
|---|---|---|---|
| Dieldrin | Fish Consumption | 2024 | TMDL priority: Medium |
| Mercury | Fish Consumption | 2024 | TMDL priority: Medium |
Reading the record
How current is Hennepin-Hopper's evidence?
11 years between the 2026 reporting cycle and monitoring through 2015
Monitoring behind at least one of these designated-use verdicts ran through 2015, 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
Hennepin-Hopper 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 1,245 assessed acres it ranks 1,947th 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 1,946 lakes with a larger one.
Still unfiled
The state has not yet filed a definitive recreation verdict and a definitive aquatic-life verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where Hennepin-Hopper 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
1,245 Top 5% larger than 95% 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 Hennepin-Hopper. 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, Hennepin-Hopper ranks 198th by listed-cause count (2 listed causes) and 28th 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 Dieldrin, 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 Hennepin-Hopper's size or cause load
Similar assessed acres
Nearest filed extents (1,245 acres here).
- Butternut Lake · 1,246 acres · WI
- Umcolcus Stream · 1,244 acres · ME
- Byllesby · 1,247 acres · MN
- Belleville Lake · 1,247 acres · MI
Similar cause load
Nearest listed-cause counts (2 here). Peers already in the acreage column are omitted.
- Aaron Mercer Reservoir · 2 causes · OR
- Abbotts Mill Pond · 2 causes · DE
- Adkins Pond · 2 causes · MD
- Adobe Creek Reservoir. · 2 causes · CO
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_WDJ. 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.