O'Leary Lake
Dakota County, Minnesota31 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for O'Leary Lake. Here is what has been measured.
- Hypereutrophic
- Eurasian watermilfoil
- 34 ft max depth
- Public access
- Limited data
O'Leary Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 153 µg/L. Chlorophyll-a (algae): 72.3 µg/L. Maximum depth: 33.5 ft. Surface area: 30.55 acres.
Minnesota DNR's Standard Survey on July 1, 2013 caught 10.00 northern pike per gill net at O'Leary Lake. Length samples in the latest survey that recorded them ran 21–30 inches. DNR survey details →
O'Leary Lake is a 31-acre highly nutrient-loaded hypereutrophic lake in Dakota County, Minnesota with a maximum depth of 34 feet (8-foot average). Water clarity is improving over recent sampling years. The lake supports 7 documented fish species including black bullhead, black crappie, and bluegill. Public access is available. Compared to the 44 other monitored lakes in Dakota County, O'Leary Lake ranks #32 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-09-18. Methodology: how these readings are compared.
What O'Leary Lake is good for
From access and monitoring records, not editorial picks.
- Fishing7 species recorded
- Ice seasonIce-out around Mar 31
- Deep water33.5 ft surveyed max depth
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether O'Leary Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for O'Leary Lake
These are the measurements Minnesota PCA publishes for O'Leary Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.6 ft of visibility. Phosphorus 153 µg/L. Chlorophyll-a 72.3 µg/L. TSI 71.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 153µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 72.3µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 71 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about O'Leary Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
O'Leary Lake typically sits around 65°F at the surface in September. Summer average is about 75°F. Usually warmest in Jul (about 78°F) and coldest in Sep (about 65°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (65°F) to its warmest (78°F).
Typical surface water temperature by month, from 13 field readings (2010–2025) via the EPA Water Quality Portal.
Minnesota DNR's Standard Survey on July 1, 2013 caught 10.00 northern pike per gill net at O'Leary Lake. Length samples in the latest survey that recorded them ran 21–30 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows O'Leary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2013-07-01 (Standard Survey).
8 surveys on file · most recent 2013-07-01 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 45.73 | 2–6 in 2013-07-01 | 0.12 lb |
| Black Bullhead | 15.08 | 9–11 in 2013-07-01 | 0.27 lb |
| Yellow Perch | 9.28 | 5–6 in 2008-07-01 | 0.11 lb |
| Black Crappie | 7.05 | 4–7 in 2013-07-01 | 0.14 lb |
| Northern Pike | 6.60 | 21–30 in 2013-07-01 | 2.72 lb |
| Hybrid Sunfish | 5.67 | 4–6 in 2013-07-01 | 0.14 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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.
Bluegill
Black Bullhead
Yellow Perch
Black Crappie
From the 2013-07-01 survey
Fish Lake is a 29 acre lake managed by the Fishing in the Neighborhood Program and the City of Eagan. The lake has a boat access (electric motors only), a fishing pier, and shore fishing areas for anglers. The lake supports a diverse fish community and was previously stocked with Channel Catfish from 1998-2002.…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for O'Leary Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — FishFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — FishFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — FishPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
33.5 ft
Average depth
8.3 ft
Surface area
31 acres
Shoreline
1.5 mi
Littoral zone
78%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Stays via Stay22
Stays near O'Leary Lake
Compare lakeside cabins, hotels, and vacation rentals near O'Leary 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around O'Leary Lake are listed below.
Top-rated places to stay near O'Leary Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing O'Leary 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.
Water Quality Trend: Stable
Based on 6 years of monitoring (2020–2025).
Water clarity
Improving6 years
Phosphorus
Stable+0.63 µg/L/yr6 years
Chlorophyll-a
Worsening+1.47 µg/L/yr6 years
Ice season
Typical ice-out
Mar 31
Earliest Mar 16, 2002 · Latest Apr 17, 2008
Typical ice-in
Nov 24
Earliest Nov 21, 2007 · Latest Nov 26, 2005
Most recent ice-out
Mar 29
2015
9 observations · Minnesota PCA ice records
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of O'Leary Lake under Clean Water Act (NPDES) discharge permits.
- Fish Lake Alum Treatment FacilityEagan · 0.4 mi away · NPDES MN0069752
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.
Nearby Lakes in Dakota County
Frequently asked questions about O'Leary Lake
Where is O'Leary Lake?
- O'Leary Lake is a lake in Dakota County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of O'Leary Lake?
- O'Leary Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 153 µg/L. Chlorophyll-a (algae): 72.3 µg/L. Maximum depth: 33.5 ft. Surface area: 30.55 acres.
Is O'Leary Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of O'Leary Lake?
- O'Leary Lake typically sits around 65°F at the surface in September, from 13 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is O'Leary Lake?
- O'Leary Lake has a maximum depth of 33.5 feet and an average depth of 8.3 feet. The lake covers 30.55 acres.
What fish are in O'Leary Lake?
- Fish species found in O'Leary Lake include black bullhead, black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, yellow perch. O'Leary Lake is located in Dakota County, Minnesota.
What did the DNR fisheries survey find at O'Leary Lake?
- Minnesota DNR's Standard Survey on July 1, 2013 caught 10.00 northern pike per gill net at O'Leary Lake. Length samples in the latest survey that recorded them ran 21–30 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows O'Leary Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
When does O'Leary Lake thaw?
- O'Leary Lake typically has ice-out around Mar 31. Ice typically forms around Nov 24. The open water season is approximately 238 days.
Can I fish at O'Leary Lake?
- Public access to O'Leary Lake is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore O'Leary Lake across LakeQuality
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Species activity outlook by water temperature and season
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Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
32 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA32 samples · 2020–2023
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity, Nephelometric Method
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate