Olson Lake

Olson Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Washington County. 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.

Mesotrophic conditions dominate at Olson Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. A maximum depth of 15 ft puts Olson Lake in the middle of Minnesota's depth distribution. The lake is compact at 87 acres, with 1.9 miles of shoreline and little volume to buffer nutrient inputs. Within Washington County's 83 graded waters, Olson Lake sits at rank 10, near the top of the local distribution.

Zebra mussels have been documented at Olson Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Olson Lake, one of 11 fish species on record for the lake. No formal public access is documented at Olson Lake — most use is by shoreline residents and their guests. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.