St. Croix 0.3 Mi. Downstream of I Lake

The LakeGrade rubric puts St. Croix 0.3 Mi. Downstream of I Lake at a C: clarity at 6.1 ft, 34 µg/L of phosphorus, and a TSI of 53 signal an intermediate trophic state. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

At a TSI of 53, St. Croix 0.3 Mi. Downstream of I Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. At 78 ft of maximum depth, St. Croix 0.3 Mi. Downstream of I Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. St. Croix 0.3 Mi. Downstream of I Lake covers 8,393 acres alongside 124.5 miles of shoreline, large enough that conditions can vary meaningfully between bays. Within the 31 graded lakes of Washington County, St. Croix 0.3 Mi. Downstream of I Lake sits at rank 26, near the bottom of the county list.

Eurasian watermilfoil has been documented at St. Croix 0.3 Mi. Downstream of I Lake, requiring shoreline management to keep dense mats from crowding native vegetation. St. Croix 0.3 Mi. Downstream of I Lake's fishery is anchored by muskellunge, with 36 documented species in total — a destination water for muskie anglers. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.