Skip to main content
LakeQuality
B

Lac Lake

Carlton County, MinnesotaMesotrophic

Lac Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

Mesotrophic conditions dominate at Lac Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. 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. Lac Lake ranks 8 of 33 in Carlton County, putting it in the upper tier of locally monitored lakes.

No invasive species are currently listed at Lac Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Lac 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 2024-07-01. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

Track Lac Lake

Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.

Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Moderate clarity, visible to about 9.5 ft. Phosphorus level: 15.5 µg/L. Chlorophyll-a: 5.5 µg/L. Trophic State Index: 45.

MetricValueGrade
Water Clarity (Secchi Depth)9.5 ftC
Phosphorus15.5 µg/LA
Chlorophyll-a (Algae)5.5 µg/LB
Trophic State Index (TSI)45Mesotrophic

Moderate nutrients, good water quality

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+1.941 m/yr5
Phosphorus Declining+5.5 µg/L/yr2
Chlorophyll-a Improving-0.98 µg/L/yr5
See year-by-year chart →

Location

Loading map…

County Ranking

Ranked #8 of 33 lakes in Carlton County

Cleaner Lakes Within 30 Miles

Lac Lake holds Grade B. One nearby lake has a higher grade.

See full comparison →

Nearby Lakes in Carlton County

DNR Reports & Resources

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

EPA Impairment Status

Lac 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_109 · 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: 2024-07-01

Monitoring stations: 1