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B

Unnamed Lake

St. Louis County, MinnesotaLimited DataMesotrophic

Unnamed Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 187 graded lakes in St. Louis County, Unnamed Lake sits at rank 47, above the county median.

Unnamed Lake has no invasive species recorded in Minnesota state databases as of 2021, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Unnamed Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. 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.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2021-10-17. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Good clarity, visible to about 11.5 ft. Trophic State Index: 42.

MetricValueGrade
Water Clarity (Secchi Depth)11.5 ftB
PhosphorusNo data
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)42Mesotrophic

Moderate nutrients, good water quality

Water Quality Trend: Stable

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable+0.023 m/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #47 of 187 lakes in St. Louis County

Cleaner Lakes Within 30 Miles

Unnamed Lake holds Grade B. 4 nearby lakes hold higher grades.

Nearby Lakes in St. Louis County

EPA Impairment Status

Unnamed Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Mercury

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN69-0939-01 · Official waterbody report · Matched by proximity (2.35 km)

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Most recent sample: 2021-10-17

Monitoring stations: 1