Pine Mountain Lake
Cass County, Minnesota1,617 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Pine Mountain Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- zebra mussel
- 80 ft max depth
- Public access
- Limited data
Pine Mountain Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12.5 ft visibility. Phosphorus: 17.5 µg/L. Chlorophyll-a (algae): 2.3 µg/L. Maximum depth: 80 ft. Surface area: 1617.31 acres.
Minnesota DNR's Standard Survey on August 4, 2025 caught 4.73 walleye per gill net at Pine Mountain Lake. Length samples in the latest survey that recorded them ran 8–25 inches. DNR survey details →
Pine Mountain Lake is a 1,617-acre mesotrophic lake in Cass County, Minnesota with a maximum depth of 80 feet. Overall water quality is improving over recent sampling years. The lake supports 16 documented fish species including black bullhead, black crappie, and bluegill. Public access is available. Compared to the 103 other monitored lakes in Cass County, Pine Mountain Lake ranks #61 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-01. Methodology: how these readings are compared.
Pine Mountain Lake covers about 1,600 acres in Cass County. The median ice-out date is April 16, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Pine Mountain Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Pine Mountain Lake is good for
From access and monitoring records, not editorial picks.
- Clear water12.5 ft of visibility
- Fishing16 species recorded
- Ice seasonIce-out around Apr 16
- Deep water80 ft surveyed max depth
- Big water1,617 acres
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. Pine Mountain Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Pine Mountain 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 Pine Mountain Lake
These are the measurements Minnesota PCA publishes for Pine Mountain Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 12.5 ft. Phosphorus 17.5 µg/L. Chlorophyll-a 2.3 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 12.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 17.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.3µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Pine Mountain Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on August 4, 2025 caught 4.73 walleye per gill net at Pine Mountain Lake. Length samples in the latest survey that recorded them ran 8–25 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Pine Mountain Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
14 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Standard Survey).
14 surveys on file · most recent 2025-08-04 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 50.72 | ||
| Yellow Perch | 26.27 | 5–9 in 2025-08-04 | 0.14 lb |
| Walleye | 10.27 | 8–25 in 2025-08-04 | 1.99 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.
Yellow Perch
Walleye
From the 2025-08-04 survey
Pine Mountain Lake (DOW # 11-0411; Lake Class 22) is a 1,612 acre lake with 737 littoral acres, 9.4 miles of shoreline, and a maximum depth of 80 feet located in Backus, MN. There is a city-owned public access on the east shore. The Minnesota Department of Natural Resources (MNDNR) has classified Minnesota's lakes…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Pine Mountain Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Pine MountainFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Pine Mountain (1464)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — Pine MountainFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Pine MountainPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
80 ft
Surface area
1,617 acres
Shoreline
9.4 mi
Littoral zone
46%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Stays via Stay22
Stays near Pine Mountain Lake
Compare lakeside cabins, hotels, and vacation rentals near Pine Mountain Lake in Cass 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 Pine Mountain 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 →
Follow Pine Mountain Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Pine Mountain Lake
- → Pine Mountain Lake fishing: DNR survey catch rates, species & stocking
- → Pine Mountain Lake fishing forecast & best times (species outlook + 14-day solunar calendar)
- → Pine Mountain Lake fishing regulations (limits, seasons, special rules)
- → Is it safe to eat fish from Pine Mountain Lake? (mercury & PFAS guide)
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: Improving
Based on 5 years of monitoring (2020–2025).
Water clarity
Improving5 years
Ice season
Typical ice-out
Apr 16
Earliest Mar 16, 2024 · Latest May 10, 2013
Typical ice-in
Nov 12
Earliest Nov 7, 1991 · Latest Dec 21, 2015
Most recent ice-out
Apr 18
2025
17 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Pine Mountain Lake is a man-made reservoir impounded by the Pine Mountain Lake (completed 1936), built primarily for recreation on the Pine River; gravity-type dam, 7 ft tall and 45 ft long.
- Surface area
- 1,612 ac
- Normal storage
- 122,120 ac-ft
- Max storage
- 126,737 ac-ft
- Drainage area
- 44.1 sq mi
- Hazard class
- Low
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN00033 · Operator website
EPA Impairment Status
Pine Mountain Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0411-00 · Official waterbody report
Nearby Lakes in Cass County
Frequently asked questions about Pine Mountain Lake
Where is Pine Mountain Lake?
- Pine Mountain Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Pine Mountain Lake?
- Pine Mountain Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 12.5 ft visibility. Phosphorus: 17.5 µg/L. Chlorophyll-a (algae): 2.3 µg/L. Maximum depth: 80 ft. Surface area: 1617.31 acres.
Is Pine Mountain Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Pine Mountain Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
How deep is Pine Mountain Lake?
- Pine Mountain Lake has a maximum depth of 80 feet. The lake covers 1617.31 acres.
What fish are in Pine Mountain Lake?
- Fish species found in Pine Mountain Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, burbot, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. Pine Mountain Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Pine Mountain Lake?
- Minnesota DNR's Standard Survey on August 4, 2025 caught 4.73 walleye per gill net at Pine Mountain Lake. Length samples in the latest survey that recorded them ran 8–25 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Pine Mountain Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
When does Pine Mountain Lake thaw?
- Pine Mountain Lake typically has ice-out around Apr 16. Ice typically forms around Nov 12. The open water season is approximately 210 days.
Can I fish at Pine Mountain Lake?
- Public access to Pine Mountain 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 Pine Mountain Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
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Where to stay at Minnesota's top lakes, each with its readings
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Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
56 measurements from 3 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA56 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (3)
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
Impairment status from EPA ATTAINS 303(d) database
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate