Flatfoot Lake
Cook County, IllinoisView mapDirections
Illinois EPA publishes the water-quality measurements for Flatfoot Lake. Here is what has been measured.
- Eutrophic
- Public access
- Limited data
Flatfoot Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 6.2 ft visibility. Phosphorus: 18 µg/L. Chlorophyll-a (algae): 21.3 µg/L.
Flatfoot Lake is a productive, nutrient-rich eutrophic lake in Cook County, Illinois. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 15 other monitored lakes in Cook County, Flatfoot Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2022-09-01. Methodology: how these readings are compared.
What Flatfoot Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Flatfoot Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Flatfoot Lake
These are the measurements Illinois EPA publishes for Flatfoot Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 6.2 ft. Phosphorus 18 µg/L. Chlorophyll-a 21.3 µg/L. TSI 52.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 6.2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 18µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 21.3µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 52 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Flatfoot Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Flatfoot Lake typically sits around 60°F at the surface in October. Summer average is about 78°F. Usually warmest in Jul (about 81°F) and coldest in Oct (about 60°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (60°F) to its warmest (81°F).
Typical surface water temperature by month, from 58 field readings (2016–2022) via the EPA Water Quality Portal. See the full Flatfoot Lake water temperature breakdown →
Recreation & Access
- Beaubien Woods - 2Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Flatfoot Lake
Compare lakeside cabins, hotels, and vacation rentals near Flatfoot Lake 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Flatfoot Lake are listed below.
Top-rated places to stay near Flatfoot Lake
Prices for Oct 23–25, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Illinois’s top lakes →
Follow Flatfoot Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Flatfoot Lake
Water quality readings over time
2 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Regulated Pollution Sources Nearby
6 EPA-permitted facilities operate within about 5 miles of Flatfoot Lake under Clean Water Act (NPDES) discharge permits. 3 facilities have a reported Clean Water Act violation in the past three years.
- River Bend Prairie LandfillDolton · 1.2 mi away · NPDES IL0075566Recent violation
- Phoenix Csos, Village OfPhoenix · 3.1 mi away · NPDES IL0072834Recent violation
- Indiana Harbor Belt RailroadRiverdale · 3.2 mi away · NPDES IL0062863Recent violation
- Riverdale Industries, Inc.Riverdale · 1.8 mi away · NPDES IL0068926
- Mittal Steel Usa-RiverdaleRiverdale · 2.3 mi away · NPDES IL0076295
- Hammond Pipeline Relocation ProjectRiverdale · 3.8 mi away · NPDES IL0080097
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.
Nearby Lakes in Cook County
Frequently asked questions about Flatfoot Lake
Where is Flatfoot Lake?
- Flatfoot Lake is a lake in Cook County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Flatfoot Lake?
- Flatfoot Lake in Cook County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Water clarity: 6.2 ft visibility. Phosphorus: 18 µg/L. Chlorophyll-a (algae): 21.3 µg/L.
Is Flatfoot Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Flatfoot Lake?
- Flatfoot Lake typically sits around 60°F at the surface in October, from 58 EPA Water Quality Portal field readings (2016–2022). That is a typical value for the month, not a live reading.
Are there boat ramps on Flatfoot Lake?
- Flatfoot Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Beaubien Woods - 2. Public access is listed as yes.
Can I fish at Flatfoot Lake?
- Flatfoot Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.
Explore Flatfoot Lake across LakeQuality
Planning a trip around Indiana Dunes?
Flatfoot Lake is about 25 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 lakes in Illinois
Other Lakes in Illinois
Eutrophic Lakes in Illinois
Where this data comes from
37 measurements from 3 monitoring stations, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- illinois epa
IL_EPA_WQX36 samples · 2020 - USGS Illinois Water Science Center
USGS-IL1 sample · 2022
Analytical methods
- Secchi disk method
- MEASURED IN FIELD
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory