Diversey Harbor Lake
Cook County, IllinoisView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Mercury
- Public access
- Limited data
Diversey Harbor Lake in Cook County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar.
- Typical in September
- 73°F
- Public access
- Yes
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Watch Diversey Harbor Lake’s letter
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Why Diversey Harbor Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Diversey Harbor Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. 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.
Diversey Harbor Lake is a lake in Cook County, Illinois. Limited fish-species data available. Public access is available with 2 public boat landings.
Source: EPA Water Quality Portal sampling records, Illinois EPA, last sampled 2023-05-23. Grade methodology: LakeQuality methodology.
What Diversey Harbor Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Diversey Harbor Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, pCBs. Check local advisories before you swim.
Water quality measurements for Diversey Harbor Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples |
Water Temperature
Diversey Harbor Lake typically sits around 73°F at the surface in September. Summer average is about 67°F. Usually warmest in Sep (about 73°F) and coldest in Nov (about 56°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 13 field readings (2013–2023) via the EPA Water Quality Portal. See the full Diversey Harbor Lake water temperature breakdown →
Recreation & Access
- Church Street Power Boat RampPublic
- Burham Harbor - NorthPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Diversey Harbor Lake
EPA Impairment Status
Diversey Harbor Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_QZI · Official waterbody report
Nearby Lakes in Cook County
Frequently asked questions about Diversey Harbor Lake
Where is Diversey Harbor Lake?
- Diversey Harbor 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 Diversey Harbor Lake?
- Diversey Harbor Lake in Cook County, Illinois is not rated for water quality — its monitoring record does not meet the evidence bar.
Is Diversey Harbor Lake safe to swim in?
- The letter is not a swimming clearance. Diversey Harbor Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, pCBs. Check local advisories before you swim.
What is the water temperature of Diversey Harbor Lake?
- Diversey Harbor Lake typically sits around 73°F at the surface in September, from 13 EPA Water Quality Portal field readings (2013–2023). That is a typical value for the month, not a live reading.
Are there boat ramps on Diversey Harbor Lake?
- Diversey Harbor Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Church Street Power Boat Ramp, Burham Harbor - North. Public access is listed as yes.
Explore Diversey Harbor Lake across LakeQuality
Planning a trip around Indiana Dunes?
Diversey Harbor Lake is about 34 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
Where this data comes from
1 measurement from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Illinois Water Science Center
USGS-IL1 sample · 2023
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
Named boat-access points from the USGS National Boat Ramps inventory