Slm Side Channel Lake
St. Clair County, IllinoisView mapDirections
Nutrients and algae run well above the regional average.
- Hypereutrophic
- Impaired · Metals (other than mercury)
- #1 of 1 in the county
- Limited data
Slm Side Channel Lake in St. Clair County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 0.8 ft visibility. Phosphorus: 317 µg/L. Chlorophyll-a (algae): 95.6 µg/L.
- Clarity
- 0.8 ft
- Typical in August
- 88°F
- Type
- Hypereutrophic
- Phosphorus
- 317 µg/L
- Chlorophyll-a
- 95.6 µg/L
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Stays near Slm Side Channel Lake
Compare lakeside cabins, hotels, and vacation rentals near Slm Side Channel Lake in St. Clair 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Slm Side Channel Lake are listed below.
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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 EPA, last sampled 2021-10-25. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The F is nutrients and algae, not a swimming clearance. Slm Side Channel Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides. Check local advisories before you swim.
Water Quality Grade: F (Algae-prone)
Very murky, less than 0.8 ft of visibility. Phosphorus 317 µg/L. Chlorophyll-a 95.6 µg/L. TSI 81. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 0.8 ft | Not graded |
| Phosphorus | 317 µg/L | Poor |
| Chlorophyll-a (Algae) | 95.6 µg/L | Poor |
| Trophic State Index (TSI) | 81 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Water Temperature
Slm Side Channel Lake typically sits around 88°F at the surface in August. Summer average is about 86°F. 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 →
Fishing Slm Side Channel Lake
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.
County Ranking
Ranked #1 of 1 lakes in St. Clair County
Nearby Lakes in St. Clair County
Frequently asked questions about Slm Side Channel Lake
Where is Slm Side Channel Lake?
- Slm Side Channel Lake is a lake in St. Clair County, Illinois. LakeQuality grades it F for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Slm Side Channel Lake?
- Slm Side Channel Lake in St. Clair County, Illinois has a water quality grade of F (Algae-prone). Water clarity: 0.8 ft visibility. Phosphorus: 317 µg/L. Chlorophyll-a (algae): 95.6 µg/L.
Is Slm Side Channel Lake safe to swim in?
- The F is nutrients and algae, not a swimming clearance. Slm Side Channel Lake is listed impaired under Clean Water Act §303(d) (IR 5) for metals (other than mercury), nutrients (phosphorus, nitrogen), pesticides. Check local advisories before you swim.
What is the water temperature of Slm Side Channel Lake?
- Slm Side Channel Lake typically sits around 88°F at the surface in August, from 66 EPA Water Quality Portal field readings (2011–2021). That is a typical value for the month, not a live reading.
Explore Slm Side Channel Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Illinois's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
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Planning a trip around Gateway Arch?
Slm Side Channel Lake is about 27 miles from Gateway Arch National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Gateway Arch →More Illinois Lake Rankings
Other Grade F Lakes in Illinois
Hypereutrophic Lakes in Illinois
Where this data comes from
22 measurements from 1 monitoring station, 2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX22 samples · 2021
Analytical methods
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)