Sauk Lake
Cook County, IllinoisView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Algal growth
- Limited data
Sauk Lake in Cook County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1 ft visibility.
- Clarity
- 1 ft
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Stays near Sauk Lake
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Watch Sauk Lake’s letter
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Why Sauk Lake has no grade
Sauk Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Sauk Lake is Not Rated — not an F. Its 1-foot median from 1 readings collected 2022 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by Illinois EPA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Sauk Lake is a lake in Cook County, Illinois.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-08-25. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Sauk Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pCBs, sediment / turbidity, turbidity. Check local advisories before you swim.
Water quality measurements for Sauk Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 1 ft of visibility. TSI 77.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 77 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Fishing Sauk Lake
Reservoir Info (USACE NID)
Sauk Lake is a man-made reservoir impounded by the Sauk Trail Lake Dam (completed 1923), built primarily for recreation on the THORN CREEK; earth-type dam, 18 ft tall and 355 ft long.
- Normal storage
- 122 ac-ft
- Max storage
- 376 ac-ft
- Hazard class
- Low
- Owner
- FOREST PRESERVE DISTRICT OF COOK COUNTY
Source: USACE National Inventory of Dams, NID ID IL00868 · Operator website · Matched by proximity (0.43 km)
EPA Impairment Status
Sauk Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RHI · Official waterbody report · Matched by proximity (0.15 km)
Regulated Pollution Sources Nearby
10 EPA-permitted facilities operate within about 5 miles of Sauk Lake under Clean Water Act (NPDES) discharge permits, including 2 classified by the EPA as major dischargers. 6 facilities have a reported Clean Water Act violation in the past three years.
- Thorn Creek Basin Sd StpChicago Heights · 2.6 mi away · NPDES IL0027723MajorRecent violation
- Aqua Illinois - University Park WwtfUniversity Park · 3.2 mi away · NPDES IL0024473MajorRecent violation
- Park Forest Excess Flow Facility, Village OfPark Forest · 1 mi away · NPDES IL0047562Recent violation
- Mid-West Manufacturing Company - Chicago HeightsChicago Heights · 2.2 mi away · NPDES IL0059421Recent violation
- Tcbsd-Homewood Excess Flow Treatment PlantHomewood · 3.1 mi away · NPDES IL0029211Recent violation
- Chicago Heights SteelChicago Heights · 3.2 mi away · NPDES IL0001678Recent 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.
Graded lakes near Sauk Lake
Sauk Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Cook County
Frequently asked questions about Sauk Lake
Where is Sauk Lake?
- Sauk Lake is a lake in Cook County, Illinois. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Sauk Lake?
- Sauk Lake in Cook County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1 ft visibility.
Is Sauk Lake safe to swim in?
- The letter is not a swimming clearance. Sauk Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pCBs, sediment / turbidity, turbidity. Check local advisories before you swim.
Explore Sauk Lake across LakeQuality
Planning a trip around Indiana Dunes?
Sauk Lake is about 31 miles from Indiana Dunes 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 Indiana Dunes →More Illinois Lake Rankings
Other Lakes in Illinois
Hypereutrophic Lakes in Illinois
Where this data comes from
1 measurement from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Illinois Water Science Center
USGS-IL1 sample · 2022
Analytical methods
- Secchi disk method
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)