What is the cleanest lake in St. Clair County, Illinois?

Round Pond in St. Clair County is the highest-rated lake in St. Clair County, Illinois with an EPA water quality grade of NR.

How are these rankings calculated?

Lakes are graded A through F on nutrients and algae — total phosphorus, nitrogen, chlorophyll-a, and turbidity — against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown; it is not the letter. Lakes without enough recent samples are UNRATED, not given an F. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in St. Clair County, Illinois

Round Pond in St. Clair County leads the rankings with a water quality grade of NR. Below are the top 6 cleanest monitored lakes in St. Clair County, Illinois, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Round Pond	St. Clair	NR	-	-	-
2	Biebell Lake	St. Clair	NR	-	-	-
3	River King Mine Lake	St. Clair	NR	-	-	-
4	Spring Lake	St. Clair	NR	-	-	-
5	Grand Marais Lake	St. Clair	NR	-	-	-
6	Brush Lake	St. Clair	NR	-	-	-

Ranked List

More Answers for St. Clair County, Illinois