Slm Side Channel Lake is a highly nutrient-loaded hypereutrophic lake in St. Clair County, Illinois. Water quality is graded F based on 2 sampling years through 2021.
Source: EPA Water Quality Portal sampling records, Illinois DNR, last sampled 2021-10-25. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 0.8 ft of visibility. Phosphorus level: 275.5 µg/L. Trophic State Index: 82.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.8 ft | F |
| Phosphorus | 275.5 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 82 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Slm Side Channel Lake
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Fishing Slm Side Channel Lake
Water Temperature
Slm Side Channel Lake averages about 86°F at the surface in summer, usually warmest in Jul (about 88°F) and coldest in Apr (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 66 field readings (2011–2021) via the EPA Water Quality Portal. See the full Slm Side Channel Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 1 lakes in St. Clair County
Cleaner Lakes Within 30 Miles
Slm Side Channel Lake holds Grade F. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in St. Clair County
Explore Slm Side Channel Lake across LakeGrade
Species activity outlook by water temperature and season
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Very high nutrients, dense algae, poor clarity
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EPA Impairment Status
Slm Side Channel 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_SOL · Official waterbody report
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Slm Side Channel Lake under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Fayetteville StpFayetteville · 3.9 mi away · NPDES IL0020893Recent violation
- Mascoutah Stp, City OfMascoutah · 4.7 mi away · NPDES IL0025291Recent violation
- St. Libory Wtp, Village OfSt. Libory · 3.3 mi away · NPDES IL0053716
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)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2021-10-25
Monitoring stations: 1