Pine Lake

Pine Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI value of 35 puts Pine Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Pine Lake is unusually deep for Minnesota at 113 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Pine Lake covers 2,122 acres alongside 18.2 miles of shoreline, large enough that conditions can vary meaningfully between bays. Within Cook County's 128 graded waters, Pine Lake sits at rank 8, near the top of the local distribution.

Pine Lake has at least one documented invasive species (spiny waterflea), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Walleye are documented at Pine Lake, one of 10 fish species on record for the lake. No formal public access is documented at Pine Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.