Opeka Lake
Cook County, WisconsinEutrophic
Opeka Lake is a productive, nutrient-rich eutrophic lake in Cook County, IL. Water quality is graded B based on 2 sampling years through 2020. Compared to the 67 other monitored lakes in Cook County, Opeka Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2020-10-06. Grade methodology: LakeGrade methodology.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Murky, only visible to about 3.9 ft. Phosphorus level: 15.5 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | D |
| Phosphorus | 15.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Location
County Ranking
Ranked #8 of 68 lakes in Cook County
Cleaner Lakes Within 30 Miles
Opeka Lake holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Cook County
More Wisconsin Lake Rankings
Other Grade B Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
EPA Impairment Status
Opeka Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IL_RGF · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-10-06
Monitoring stations: 3