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C

East Twin Lake

St. Louis County, MinnesotaEutrophic

East Twin Lake sits at a C on the grading scale — not impaired, not pristine, with summer measurements that vary year to year. Secchi readings are the weakest of the scored parameters, suggesting suspended sediment or algal biomass dominates the optical signal.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. 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. East Twin Lake sits at rank 134 of 187 in St. Louis County, in the lower half of the local distribution.

East Twin Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for East Twin 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. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-07-30. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Generally safe for swimming, moderate water quality

Water Quality Grade: C, Fair

Very murky, less than 2.8 ft of visibility. Phosphorus level: 34 µg/L. Chlorophyll-a: 6.9 µg/L. Trophic State Index: 56.

MetricValueGrade
Water Clarity (Secchi Depth)2.8 ftF
Phosphorus34 µg/LC
Chlorophyll-a (Algae)6.9 µg/LB
Trophic State Index (TSI)56Eutrophic

High nutrients, frequent algae, reduced clarity

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+0.854 m/yr5
Phosphorus Improving-2.5 µg/L/yr2
Chlorophyll-a Improving-1.07 µg/L/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #134 of 187 lakes in St. Louis County

Cleaner Lakes Within 30 Miles

East Twin Lake holds Grade C. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in St. Louis County

State Parks Near East Twin Lake

Eutrophic Lakes in Minnesota

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for East Twin Lake. 1 report on file.

EPA Impairment Status

East Twin Lake is officially listed as impaired under Clean Water Act §303(d) in the 2019 EPA reporting cycle.

Causes of impairment

Mercury

Source: EPA ATTAINS assessment unit FDL_105 · Official waterbody report

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: 2024-07-30

Monitoring stations: 1