Second Lake
Second Lake in Carlton County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 1.2 ft visibility. Phosphorus: 75 µg/L. Chlorophyll-a (algae): 13 µg/L.
- Clarity
- 1.2 ft
- Typical in August
- 67°F
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Second Lake →
Next lake in Carlton County
Second Lake is a productive, nutrient-rich eutrophic lake in Carlton County, Minnesota. Water quality is graded D based on 2 sampling years through 2024. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 21 other monitored lakes in Carlton County, Second Lake ranks #21 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-07-01. Grade methodology: LakeGrade methodology.
Watch Second Lake water quality
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Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 1.2 ft of visibility. Phosphorus level: 75 µg/L. Chlorophyll-a: 13 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.2 ft | Not graded |
| Phosphorus | 75 µg/L | Poor |
| Chlorophyll-a (Algae) | 13 µg/L | Fair |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Second Lake
Compare lakeside cabins, hotels, and vacation rentals near Second Lake in Carlton 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Second Lake are listed below.
Top-rated places to stay near Second Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Second Lake typically sits around 67°F at the surface in August. Summer average is about 67°F. Usually warmest in Jul (about 71°F) and coldest in May (about 56°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 19 field readings (2010–2021) via the EPA Water Quality Portal. See the full Second Lake water temperature breakdown →
Recreation & Access
- CloquetPublic
Fishing Second Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.148 m/yr | 5 |
| Phosphorus | ↓ Declining | +20.9 µg/L/yr | 4 |
| Chlorophyll-a | → Stable | 0 µg/L/yr | 5 |
EPA Impairment Status
Second Lake is officially listed as impaired under Clean Water Act §303(d) in the 2019 EPA reporting cycle.
Causes of impairment
Source: EPA ATTAINS assessment unit FDL_116 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Second Lake under Clean Water Act (NPDES) discharge permits.
- Jarden Home BrandsCloquet · 2.5 mi away · NPDES MN0000337
- Sappi Cloquet LlcCloquet · 3.3 mi away · NPDES MN0001431
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #21 of 22 lakes in Carlton County
Nearby Lakes With Higher Grades
Second Lake holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Carlton County
Frequently asked questions about Second Lake
What is the water quality grade for Second Lake?
- Second Lake in Carlton County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 1.2 ft visibility. Phosphorus: 75 µg/L. Chlorophyll-a (algae): 13 µg/L.
Is Second Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Second Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 13 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Second Lake?
- Second Lake typically sits around 67°F at the surface in August, from 19 EPA Water Quality Portal field readings (2010–2021). That is a typical value for the month, not a live reading.
Are there boat ramps on Second Lake?
- Second Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Cloquet. Public access is listed as yes.
Explore Second Lake across LakeGrade
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Species activity outlook by water temperature and season
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High nutrients, frequent algae, reduced clarity
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Where this data comes from
60 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Fond du Lac Band of Chippewa (MN)
FONDULAC_WQX60 samples · 2020–2024
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- Phosphorus by Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
- 10200 H ~ Chlorophyll a-b-c Determination
- Color, APHA Platinum-Cobalt
- For determination of Copper by the Bicinchoninate 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Named boat-access points from the USGS National Boat Ramps inventory