Ace Lake
Ace Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8 ft visibility. Maximum depth: 8 ft. Surface area: 317.76 acres.
- Clarity
- 8 ft
- Max depth
- 8 ft
- Area
- 318 acres
- Trend
- ↑ Improving
- Public access
- No
Next lake in St. Louis County
Why Ace Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Ace Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Ace Lake is a 318-acre lake in St. Louis County, Minnesota with a maximum depth of 8 feet (3-foot average). Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-07-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Ace Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Moderate clarity, visible to about 8 ft. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Ace Lake
Compare lakeside cabins, hotels, and vacation rentals near Ace Lake in St. Louis County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Ace Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 8 ft |
| Average Depth | 3 ft |
| Surface Area | 318 acres |
| Shoreline Length | 5.5 mi |
| Littoral Zone | 100% |
| Public Access | No |
Fishing Ace Lake
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1997-08-04 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| White Sucker | 25.00 | 2.31 lb |
| Northern Pike | 6.88 | 2.73 lb |
| Yellow Perch | 4.46 | 0.12 lb |
| Walleye | 3.92 | 1.54 lb |
| Rock Bass | 2.67 | 0.57 lb |
| Pumpkinseed | 0.42 | 0.4 lb |
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.
White Sucker
Northern Pike
Yellow Perch
Walleye
From the 1997-08-04 survey
King is a 293 acre lake located 4 miles south of Rollins, MN off county #266. Stewart has difficult access from the Rossini Trail across a minimum maintenance road to the south side of the lake. Maximum depth is 8 feet and 99% of the lake is shallower than 15 feet. Walleye abundance indexed with assessment nets was…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ace Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — KingFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — KingFish Stocking History · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.269 m/yr | 4 |
EPA Impairment Status
Ace Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4C).
Causes of impairment
Source: EPA ATTAINS assessment unit MN69-0016-00 · Official waterbody report · Matched by proximity (2.4 km)
Graded lakes near Ace Lake
Ace Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Ace Lake
What is the water quality grade for Ace Lake?
- Ace Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 8 ft visibility. Maximum depth: 8 ft. Surface area: 317.76 acres.
Is Ace Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Ace Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Ace Lake?
- Ace Lake has a maximum depth of 8 feet and an average depth of 3 feet. The lake covers 317.76 acres.
Explore Ace Lake across LakeGrade
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Where this data comes from
11 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA11 samples · 2021–2025
Analytical methods
- Field measurement/observation, generic method
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake details from Minnesota DNR LakeFinder