Sanburn Lake
Cass County, MinnesotaLimited DataOligotrophic
Sanburn Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota.
A TSI value of 35 puts Sanburn Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake bottoms out at 48 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Sanburn Lake covers 220 acres alongside 2.5 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Cass County's 132 graded waters, Sanburn Lake sits at rank 18, near the top of the local distribution.
No invasive species are currently listed at Sanburn Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Sanburn Lake, one of 12 fish species on record for the lake. A documented public access point at Sanburn Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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 2024-07-06. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 19 ft down. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 19 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 48 ft |
| Surface Area | 220.31 acres |
| Shoreline Length | 2.5 mi |
| Littoral Zone | 38% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for Sanburn Lake (14-day solunar calendar)
→ Is it safe to eat fish from Sanburn Lake? (mercury & PFAS guide)
→ Sanburn Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.25 m/yr | 5 |
| Phosphorus | ↓ Declining | +7 µg/L/yr | 2 |
Location
County Ranking
Ranked #18 of 132 lakes in Cass County
Nearby Lakes in Cass County
More Minnesota Lake Rankings
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2022-07-07 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| MMS | 465.27 | — |
| Bluntnose Minnow | 49.31 | — |
| Bluegill | 31.86 | 0.16 lb |
| Yellow Bass | 10.04 | 0.53 lb |
| Largemouth Bass | 9.11 | 0.48 lb |
| BCS | 8.13 | — |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Yellow Bass
Largemouth Bass
From the 2022-07-07 survey
A targeted survey of nearshore fish species in Sanborn Lake was conducted on July 21, 2022 by Index of Biological Integrity (IBI) Program Staff. Sampling sites were evenly spaced around the lake and each was sampled by backpack electrofishing and seining with a 50-foot seine, where possible. Backpack electrofishing…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Sanburn Lake. 4 reports on file.
- —Fisheries Lake Survey — SanbornFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Sanborn (1463)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — SanbornFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — SanbornPublic Water Access Sites · MN DNR LakeFinder
EPA Impairment Status
Sanburn Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0308-01 · Official waterbody report · Matched by proximity (2.86 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
Lake details from Minnesota DNR LakeFinder
Most recent sample: 2024-07-06
Monitoring stations: 1