Lake Opeka is a productive, nutrient-rich eutrophic lake in Cook County, Illinois. Water quality is graded D based on 1 sampling years through 2022. Overall water quality is declining over recent sampling years. Compared to the 67 other monitored lakes in Cook County, Lake Opeka ranks #15 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2022-09-22. Grade methodology: LakeGrade methodology.
Watch Lake Opeka water quality
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Murky, only visible to about 4 ft. Trophic State Index: 57.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 57 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Opeka
Compare lakeside cabins, hotels, and vacation rentals near Lake Opeka in Cook County, Illinois — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lake Opeka
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Fishing Lake Opeka
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -21.5 m/yr | 2 |
Water Temperature
Lake Opeka averages about 77°F at the surface in summer, usually warmest in Jul (about 79°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 43 field readings (2020–2022) via the EPA Water Quality Portal. See the full Lake Opeka water temperature breakdown →
Location
County Ranking
Ranked #15 of 68 lakes in Cook County
Cleaner Lakes Within 30 Miles
Lake Opeka holds Grade D. 2 nearby lakes hold higher grades.
Nearby Lakes in Cook County
Explore Lake Opeka across LakeGrade
More Illinois Lake Rankings
Other Grade D Lakes in Illinois
Eutrophic Lakes in Illinois
More records, surveys & data sources
EPA Impairment Status
Lake Opeka 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
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
12 EPA-permitted facilities operate within about 5 miles of Lake Opeka under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 7 facilities have a reported Clean Water Act violation in the past three years.
- Mwrdgc- James Kirie WrpDes Plaines · 2 mi away · NPDES IL0047741MajorRecent violation
- Bensenville - South Stp, Village OfBensenville · 4.8 mi away · NPDES IL0021849MajorRecent violation
- Blackhawk Estates Mobile Home Community StpChicago · 1.8 mi away · NPDES IL0049859Recent violation
- Des Plaines Mobile Home Park StpDes Plaines · 2.2 mi away · NPDES IL0054160Recent violation
- Aircraft Service International Inc. D/B/A Menzies AviationChicago · 2.3 mi away · NPDES IL0066567Recent violation
- Aircraft Service International IncChicago · 2.4 mi away · NPDES IL0080235Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-22
Monitoring stations: 1