Cobblestone Lake
Cobblestone Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 93 µg/L. Chlorophyll-a (algae): 17.5 µg/L. Maximum depth: 18 ft. Surface area: 34.73 acres.
- Clarity
- 3.9 ft
- Typical in August
- 71°F
- Max depth
- 18 ft
- Area
- 35 acres
- Type
- Eutrophic
- Public access
- No
Next lake in Dakota County
Cobblestone Lake is a 35-acre productive, nutrient-rich eutrophic lake in Dakota County, Minnesota with a maximum depth of 18 feet. Water quality is graded C based on 1 sampling years through 2024. The lake supports 10 documented fish species including black bullhead, black crappie, and bluegill. No public access — the lake is private or restricted. Compared to the 44 other monitored lakes in Dakota County, Cobblestone Lake ranks #22 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-06. Grade methodology: LakeGrade methodology.
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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.
Swim with caution, moderate algae may be present
Water Quality Grade: C (Fair)
Murky, only visible to about 3.9 ft. Phosphorus level: 93 µg/L. Chlorophyll-a: 17.5 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 93 µg/L | Not graded |
| Chlorophyll-a (Algae) | 17.5 µg/L | Fair |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Cobblestone Lake
Compare lakeside cabins, hotels, and vacation rentals near Cobblestone Lake in Dakota 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 Cobblestone Lake
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Water Temperature
Cobblestone Lake typically sits around 71°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 77°F) and coldest in Oct (about 55°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 27 field readings (2010–2024) via the EPA Water Quality Portal. See the full Cobblestone Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 18 ft |
| Surface Area | 35 acres |
| Shoreline Length | 1.3 mi |
| Public Access | No |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Cobblestone Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
EPA Impairment Status
Cobblestone 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 MN19-0349-00 · Official waterbody report · Matched by proximity (1.67 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Cobblestone Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger.
- Met Council - Empire WrrfFarmington · 4.7 mi away · NPDES MN0045845Major
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 #22 of 45 lakes in Dakota County
Nearby Lakes With Higher Grades
Cobblestone Lake holds Grade C. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Dakota County
Frequently asked questions about Cobblestone Lake
What is the water quality grade for Cobblestone Lake?
- Cobblestone Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 93 µg/L. Chlorophyll-a (algae): 17.5 µg/L. Maximum depth: 18 ft. Surface area: 34.73 acres.
Is Cobblestone Lake safe to swim in?
- Swim with caution, moderate algae may be present. Cobblestone Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 17.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Cobblestone Lake?
- Cobblestone Lake typically sits around 71°F at the surface in August, from 27 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Cobblestone Lake?
- Cobblestone Lake has a maximum depth of 18 feet. The lake covers 34.73 acres.
What fish are in Cobblestone Lake?
- Fish species found in Cobblestone Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, pumpkinseed, walleye, white sucker, yellow perch. Cobblestone Lake is located in Dakota County, Minnesota.
Explore Cobblestone Lake across LakeGrade
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High nutrients, frequent algae, reduced clarity
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Where this data comes from
12 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
MNPCA12 samples · 2024
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
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)
Lake details from Minnesota DNR LakeFinder