Fourth Lake
Fourth Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.5 ft visibility. Maximum depth: 20 ft. Surface area: 204.9 acres.
- Clarity
- 1.5 ft
- Max depth
- 20 ft
- Area
- 205 acres
- Trend
- ↓ Declining
- Public access
- No
Next lake in St. Louis County
Why Fourth 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 Fourth 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.
Fourth Lake is a 205-acre lake in St. Louis County, Minnesota with a maximum depth of 20 feet. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-09. 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 Fourth Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Very murky, less than 1.5 ft of visibility. Trophic State Index: 72.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 72 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Fourth Lake
Compare lakeside cabins, hotels, and vacation rentals near Fourth 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.
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 20 ft |
| Surface Area | 205 acres |
| Shoreline Length | 7.8 mi |
| Littoral Zone | 86% |
| Public Access | No |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Fourth Lake
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.327 m/yr | 4 |
EPA Impairment Status
Fourth Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MN69-0565-00 · Official waterbody report · Matched by proximity (1.22 km)
Graded lakes near Fourth Lake
Fourth Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Fourth Lake
What is the water quality grade for Fourth Lake?
- Fourth Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 1.5 ft visibility. Maximum depth: 20 ft. Surface area: 204.9 acres.
Is Fourth Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Fourth 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 Fourth Lake?
- Fourth Lake has a maximum depth of 20 feet. The lake covers 204.9 acres.
What fish are in Fourth Lake?
- Fish species found in Fourth Lake include black bullhead, black crappie, bluegill, brown bullhead, channel catfish, northern pike, pumpkinseed, rock bass, shorthead redhorse, walleye, white sucker, yellow bullhead, yellow perch. Fourth Lake is located in St. Louis County, Minnesota.
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Where this data comes from
9 measurements from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA9 samples · 2024
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 size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder