Is Onalaska, WA Tap Water Safe to Drink?
Graded C+, with 9 unresolved violations on record. See what was cited — and what it means for your tap. What to do next ↓
69.4/100
waterverge.com Onalaska, WA — Water Quality Report
Onalaska's drinking water received a grade of C+ (69.4 out of 100), indicating fair water quality. The city's 1 water system serves approximately 1,983 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 516 violations on record, including 2 health-based violations. 9 remain unresolved.
What to know about Onalaska's water
Onalaska ranks #168 out of 294 cities in Washington for water quality, placing it below average in the state.
Onalaska 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.
As a small community water system, Onalaska may have fewer resources for advanced treatment technologies and infrastructure upgrades compared to larger utilities.
Water quality score
See methodology →Is Onalaska, WA water safe to drink?
Onalaska's drinking water has significant quality concerns based on EPA testing data. With a grade of C+ (69.4/100), the system has issues across multiple categories. A water filter is recommended for all residents. The city's 1 water system serves approximately 1,983 residents using groundwater (wells).
Recent water quality updates for Onalaska
A timeline of significant water quality events, violations, and data updates.
Latest EPA compliance and testing data incorporated into Onalaska's water quality assessment. Grade: C+ (69.4/100).
Federal disaster declaration (FEMA DR-3629). Flood event — may have impacted local water infrastructure.
Federal disaster declaration (FEMA DR-4650). Flood event — may have impacted local water infrastructure.
Contaminants: Revised Total Coliform Rule.
Contaminants: Consumer Confidence Rule.
Contaminants: TTHM, Total Haloacetic Acids (HAA5).
Key contaminant findings
Based on the most recent EPA sampling data for Onalaska's water supply.
Well within EPA limits.
Violation history
Onalaska's water system has 516 total violations on record, including 2 health-based violations. 9 remain unresolved.
Flood & environmental risk
Lewis County has experienced 10 federally declared disasters since 1991. 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 South Fork Newaukum River, Nf Newaukum River Above Bear Creek, Cowlitz River Below Mayfield Dam.
Where does Onalaska's water come from?
Onalaska's drinking water comes from groundwater (wells), supplied by 1 water system serving approximately 1,983 people. Groundwater is generally less susceptible to surface contamination but can contain naturally occurring contaminants like arsenic, radon, and nitrate. Nearby water bodies include South Fork Newaukum River (river), Nf Newaukum River Above Bear Creek (river), Cowlitz River Below Mayfield Dam (river).
What Onalaska residents can do
Recommended: NSF-certified water filter. This addresses the specific contaminants found in Onalaska'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.
Onalaska'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
Flood & disaster history
Lewis County has experienced 10 federally declared disasters since 1991. Flooding and severe weather can compromise water treatment infrastructure and introduce contaminants into drinking water supplies.
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 |
Lead level trend (90th percentile)
See how Onalaska compares by contaminant
Explore where Onalaska ranks among all Washington cities for specific contaminants.
Water source & infrastructure
Where Onalaska's water comes from
Onalaska'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 local government ownership and serves approximately 1,983 people through 1 water system.
Water bodies near Onalaska
Onalaska is located near 3 notable water bodies. These water bodies contribute to the regional watershed and may indirectly affect groundwater quality.
Water systems serving Onalaska
| System Name | PWSID | Population | Source |
|---|---|---|---|
| LEWIS CO WATER DIST #2 | WA5347001 | 1,983 | GW |
How Onalaska compares
Full Washington rankings →Onalaska's score of 69.4/100 is above the average of 53/100 among major Washington cities. It outscores 7 of 10 nearby cities.
Nearby cities
View Washington rankings →About Onalaska, WA
Learn more about your water
Guides and resources related to Onalaska's water quality findings.
Explore water quality across Lewis
Frequently asked questions
Is Onalaska, WA tap water safe to drink?
Onalaska's water quality earned a grade of C+ (69.4/100). Some concerns have been identified. Consider a water filter for an extra layer of protection. The city ranks #168 out of 294 cities tested in Washington.
What contaminants are in Onalaska's water?
Lead was measured at 0.0 ppb (90th percentile). 516 violations are on record.
How is Onalaska'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 Onalaska?
Based on current data, basic filtration should suffice for additional peace of mind.
Where does Onalaska's water come from?
Onalaska's water is sourced from Groundwater. The city has 1 water system serving approximately 1,983 residents.
What health violations has Onalaska's water system had?
Onalaska has 2 health-based violations on record. The most recent violation was recorded in November 2016. Health-based violations mean the water exceeded EPA maximum contaminant levels (MCLs) for a regulated substance. 9 violations remain unresolved.
Is Onalaska's groundwater at risk of contamination?
Onalaska 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 516 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 Onalaska's water compare to other cities?
Onalaska ranks #168 out of 294 cities in Washington (better than 43% of state cities) and #10922 out of 15744 cities nationally (31th percentile). The grade of C+ reflects the combined assessment of violation history, lead and copper levels, PFAS contamination, and regulatory compliance.
Does Onalaska's small water system affect quality?
Onalaska's system serves approximately 1,983 residents. Small community water systems (under 3,300 people) may have fewer financial resources for infrastructure upgrades and advanced treatment technologies. However, they are held to the same EPA drinking water standards as larger systems. This system has 516 violations on record.