Is Cass Lake, MN Tap Water Safe to Drink?
Graded C- — but Copper was detected above EPA limits. Here's what's in the water and how to remove it. What to do next ↓
56.1/100
waterverge.com Cass Lake, MN — Water Quality Report
Cass Lake's drinking water received a grade of C- (56.1 out of 100), indicating poor water quality. The city's 8 water systems serve approximately 3,588 residents using groundwater.
Lead levels were measured at 0.0 ppb (90th percentile), well within EPA limits. This system has not yet been tested for PFAS under the EPA UCMR 5 program.
The system has 142 violations on record, including 17 health-based violations. 25 remain unresolved.
What to know about Cass Lake's water
Cass Lake ranks #455 out of 466 cities in Minnesota for water quality, placing it among the lowest-rated in the state.
Cass Lake relies on groundwater, which is generally less vulnerable to surface contamination but can be affected by naturally occurring minerals like arsenic and nitrate, as well as agricultural and industrial runoff.
The system has seen 23 violations in the past five years, suggesting a pattern of compliance challenges that residents should monitor closely.
Water quality score
See methodology →Is Cass Lake, MN water safe to drink?
Cass Lake's drinking water has significant quality concerns based on EPA testing data. With a grade of C- (56.1/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 8 water systems serve approximately 3,588 residents using groundwater (wells).
Recent water quality updates for Cass Lake
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Cass Lake's water quality assessment. Grade: C- (56.1/100).
Contaminants: Chlorine, Revised Total Coliform Rule.
Federal disaster declaration (FEMA DR-4797). Flood event — may have impacted local water infrastructure.
1 health-based. Contaminants: Lead and Copper Rule.
Contaminants: CYANIDE.
Federal disaster declaration (FEMA DR-4390). Flood event — may have impacted local water infrastructure.
Key contaminant findings
Based on the most recent EPA sampling data for Cass Lake's water supply.
Well within EPA limits.
Exceeds EPA action level. Copper can leach from household plumbing — flush taps for 30 seconds before drinking.
Violation history
Cass Lake's water system has 142 total violations on record, including 17 health-based violations. 25 remain unresolved. 23 violations were issued in the last 5 years.
Flood & environmental risk
Cass County has experienced 6 federally declared disasters since 1965. Flooding and severe storms can overwhelm water treatment plants, cause sewage overflows, and introduce agricultural runoff, bacteria, and sediment into drinking water supplies. Local water sources include Mississippi River.
Where does Cass Lake's water come from?
Cass Lake's drinking water comes from groundwater (wells), supplied by 8 water systems serving approximately 3,588 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include Mississippi River (river).
What Cass Lake residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Cass Lake's water.
Your water utility is required to publish an annual Consumer Confidence Report (CCR) with detailed testing results. Ask for the latest copy or check your utility's website.
Cass Lake's area has a history of flooding. After severe weather, watch for boil water advisories from your local utility.
Data: EPA SDWIS, UCMR 5 (PFAS), FEMA, NOAA. Last updated May 2026.
Top contaminants to know
View all ↓Violation summary
Violations & advisories
Top industrial polluters within 10 miles of Cass Lake
Industrial polluters nearby
Reported releases to surface water by facilities near Cass Lake, ranked by pounds discharged annually.
| Facility | Top chemical | To surface water (lbs/yr) | Distance |
|---|---|---|---|
POTLATCHDELTIC LAND & LUMBER LLC - BEMIDJI LUMBERMILL BEMIDJI, MN56601 | — | — | 7.3 mi |
Source: EPA Toxic Release Inventory (TRI) 2023
Superfund sites within 10 miles of Cass Lake
Superfund sites nearby
Federally tracked hazardous-waste sites on the EPA National Priorities List. Proximity does not necessarily indicate tap-water contamination — the connection depends on hydrology and treatment.
- ST REGIS PAPER CO0.4 mi
Source: EPA Superfund National Priorities List
Drought conditions
D1 — moderate droughtCass County is currently in D1 (moderate drought) per the U.S. Drought Monitor (week of May 5, 2026). Drought can elevate disinfection-byproduct (TTHM/HAA5) levels and taste/odor issues as utilities draw from lower reservoirs.
Source: U.S. Drought Monitor, updated weekly by NDMC, USDA, and NOAA.
Flood & disaster history
Cass County has experienced 6 federally declared disasters since 1965. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
Recommended water filters
Based on contaminants detected in Cass Lake's water supply, we recommend the following filter types.
Full contaminants report
| Contaminant | Detected Level | EPA Limit | Unit | Category | Status |
|---|---|---|---|---|---|
| Lead (90th percentile) LeadHeavy Metal A toxic heavy metal that can leach into drinking water from older pipes, solder, and fixtures. No amount of lead in water is considered safe. Health EffectsBrain and nervous system damage in children, kidney damage, high blood pressure, and reproductive problems in adults. EPA Limit15 ppb action level Common SourcesCorrosion of lead pipes, lead solder, brass faucets, and household plumbing. | 0.0 | 15 | ppb | Inorganic | Safe |
| Copper (90th percentile) CopperInorganic A metal that enters drinking water mainly through corrosion of copper plumbing. Small amounts are essential for health, but excess levels are harmful. Health EffectsGastrointestinal distress (nausea, vomiting, diarrhea) at short-term high levels; liver and kidney damage from long-term exposure. EPA Limit1.3 mg/L action level Common SourcesCorrosion of copper household plumbing, erosion of natural deposits. | 1.67 | 1.3 | mg/L | Inorganic | Over Limit |
Lead level trend (90th percentile)
Copper level (90th percentile)
Latest reading: 1.670 mg/L (2022)
EPA action level: 1.3 mg/L
See how Cass Lake compares by contaminant
Explore where Cass Lake ranks among all Minnesota cities for specific contaminants.
Water source & infrastructure
Where Cass Lake's water comes from
Cass Lake's drinking water is drawn from underground aquifers through wells.
Groundwater is naturally filtered through rock and soil layers, generally requiring less treatment than surface water. However, it can contain naturally occurring contaminants like arsenic, radon, and minerals.
Agricultural activity, septic systems, and industrial operations near well fields can introduce nitrates, pesticides, and volatile organic compounds.
The system is operated by native american ownership and serves approximately 3,588 people through 8 water systems.
Water bodies near Cass Lake
Cass Lake is located near 1 notable water body. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Cass Lake
| System Name | PWSID | Population | Source |
|---|---|---|---|
| NORTHSIDE | 055294214 | 2,086 | GW |
| Cass Lake | MN1110006 | 691 | GW |
| BALL CLUB | 055294201 | 333 | GW |
| INGER | 055294204 | 186 | GW |
| BENA | 055294202 | 112 | GW |
| PLANTATION | 055294205 | 105 | GW |
| OAK POINT | 055294207 | 45 | GW |
| OLD AGENCY | 055294208 | 30 | GW |
How Cass Lake compares
Full Minnesota rankings →Cass Lake's score of 56.1/100 is below the average of 82/100 among major Minnesota cities. 10 of 10 nearby cities score higher.
Nearby cities
View Minnesota rankings →ZIP codes served by Cass Lake
The water systems serving Cass Lake cover 1 ZIP code. Select any ZIP to see which water systems serve that area.
About Cass Lake, MN
Wikipedia →Cass Lake is a city in Cass County, Minnesota, United States, located within the boundaries of the Leech Lake Indian Reservation. It is surrounded by Pike Bay Township. Cass Lake had a population of 675 in the 2020 census. It is notable as the headquarters location of Minnesota Chippewa Tribe and Leech Lake Band of Ojibwe, as well as the Chippewa National Forest.
Learn more about your water
Guides and resources related to Cass Lake's water quality findings.
Explore water quality across Cass
Frequently asked questions
Is Cass Lake, MN tap water safe to drink?
Cass Lake's water quality earned a grade of C- (56.1/100). Significant issues have been found. A water filter is strongly recommended. The city ranks #455 out of 466 cities tested in Minnesota.
What contaminants are in Cass Lake's water?
Lead was measured at 0.0 ppb (90th percentile). 142 violations are on record.
How is Cass Lake's water quality grade calculated?
The grade is based on four factors: violation history (40%), lead and copper levels (25%), PFAS contamination (25%), and regulatory compliance (10%). The score is also adjusted based on how complete the available data is. See our methodology page for full details.
Do I need a water filter in Cass Lake?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Cass Lake's water come from?
Cass Lake's water is sourced from Groundwater. The city has 8 water systems serving approximately 3,588 residents.
What health violations has Cass Lake's water system had?
Cass Lake has 17 health-based violations on record. The most recent violation was recorded in October 2024. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 25 violations remain unresolved.
Is Cass Lake's groundwater at risk of contamination?
Cass Lake uses groundwater, which can be affected by naturally occurring contaminants like arsenic, radon, and nitrate, as well as agricultural runoff and industrial activity. The system has 142 violations on record that may relate to groundwater quality. Groundwater systems are generally less susceptible to surface contamination but should be monitored for emerging contaminants like PFAS.
How does Cass Lake's water compare to other cities?
Cass Lake ranks #455 out of 466 cities in Minnesota (better than 2% of state cities) and #12481 out of 15744 cities nationally (21th percentile). The grade of C- reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.