Pine Mountain Lake
Pine Mountain Lake in Cass County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 12.5 ft
- Max depth
- 80 ft
- Area
- 1,617 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 16
- Open water
- 210 days
Next lake in Cass County
Pine Mountain Lake is a 1,617-acre mesotrophic lake in Cass County, Minnesota with a maximum depth of 80 feet. Water quality is graded A based on 2 sampling years through 2025. 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 with 1 public boat landing. 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. 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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 12.5 ft. Phosphorus level: 17.5 µg/L. Chlorophyll-a: 2.3 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12.5 ft | Not graded |
| Phosphorus | 17.5 µg/L | Good |
| Chlorophyll-a (Algae) | 2.3 µg/L | Good |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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.
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 80 ft |
| Surface Area | 1,617 acres |
| Shoreline Length | 9.4 mi |
| Littoral Zone | 46% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- DeerfieldPublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Pine Mountain 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.
DNR Fisheries Survey Summary
14 surveys on file from MN DNR Fisheries. Most recent: 2025-08-04 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 50.72 | — |
| Yellow Perch | 26.27 | 0.14 lb |
| SFS | 23.21 | — |
| MMS | 18.12 | — |
| JND | 11.23 | — |
| Walleye | 10.27 | 1.99 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.315 m/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (17 observations).
Estimated open water season: 210 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-16 (2024) | 2013-05-10 (2013) |
| Ice-In | 1991-11-07 (1991) | 2015-12-21 (2015) |
Most recent ice-out: 2025-04-18
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0411-00 · Official waterbody report
County Ranking
Ranked #61 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Pine Mountain Lake
What is the water quality grade for Pine Mountain Lake?
- Pine Mountain Lake in Cass County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Pine Mountain Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.3 µg/L. Always check local health department advisories before swimming.
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.
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.
Are there boat ramps on Pine Mountain Lake?
- Pine Mountain Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Deerfield. Public access is listed as yes.
Explore Pine Mountain Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded 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 grade
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Moderate nutrients, good water quality
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More Minnesota Lake Rankings
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate