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LakeQuality
Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
D

Will County Lake Quality

Illinois, 7 lakes, average grade D (Nutrient-rich)

Will County holds 7 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Monee Lake (D) is the cleanest in the county.

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All Lakes in Will County

7 lakes · 1 graded, 6 not rated1 graded lake · 6 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicAccess
1DMonee LakeWillD4.9 ft139 µg/L16.7 µg/LNo recent samples✓ Public
NRLake RenwickWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLake PlainfieldWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRWhalon LakeWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRMilliken LakeWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBraidwood Power Plant Cooling PondWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRHawk LakeWillNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded

NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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Source: EPA National Aquatic Resource Surveys, 2026.