Thunder Bay District County, Ontario · Water Quality Report Card
Circle L. Lake
Circle L. Lake in Thunder Bay District, Ontario received a water quality grade of B (Good). Water clarity: 2.1 m visibility. Phosphorus: 10.5 µg/L.
- Clarity
- 2.1 m
- Type
- Mesotrophic
Circle L. Lake is a mesotrophic lake in Thunder Bay District County, Ontario. Water quality is graded B based on 2 sampling years through 2025. Compared to the 301 other monitored lakes in Thunder Bay District County, Circle L. Lake ranks #151 for water quality.
Source: EPA Water Quality Portal sampling records, Ontario MECP, last sampled 2025-08-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 6.9 ft. Phosphorus level: 10.5 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.1 m | C |
| Phosphorus | 10.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Circle L. Lake
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Fishing Circle L. Lake
Location
County Ranking
Ranked #151 of 302 lakes in Thunder Bay District
Cleaner Lakes Within 30 Miles
Circle L. Lake holds Grade B. 2 nearby lakes hold higher grades.
- AParks LakeThunder Bay District · 7.2 mi · Higher grade (B → A)
- ADisraeli LakeThunder Bay District · 16 mi · Higher grade (B → A)
Nearby Lakes in Thunder Bay District
Explore Circle L. Lake across LakeGrade
More Ontario Lake Rankings
Other Grade B Lakes in Ontario
Mesotrophic Lakes in Ontario
More records, surveys & data sources
Where this data comes from
Measurements for Circle L. Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Data Sources
Water quality data from the EPA Water Quality Portal
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2025-08-01
Monitoring stations: