What is the cleanest lake in Washington County, Oregon?

Stimson Millpond in Washington County is the highest-rated lake in Washington County, Oregon 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 Washington County, Oregon

Stimson Millpond in Washington County leads the rankings with a water quality grade of NR. Below are the top 2 cleanest monitored lakes in Washington County, Oregon, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Stimson Millpond	Washington	NR	-	-	-
2	Barney Reservoir	Washington	NR	-	-	-

Ranked List

More Answers for Washington County, Oregon