Onalaska Waterworks
EPA ID: WI6320327 · 18,000 people served · 4 ZIP codes
ZipCheckup's reading of EPA records for Onalaska Waterworks (WI6320327): no drinking-water violations recorded since 2021. Onalaska Waterworks has no EPA violations on record; the utility serves 18,000 residents.
Data: EPA SDWIS
Service Area Map
Coverage area for Onalaska Waterworks Source: EPA SDWIS service area boundaries.
Service area boundary - average Home Safety grade of mapped ZIPs: B
Demographics of ZIP Codes Served
The ZIP codes associated with Onalaska Waterworks have a median household income of $88,206 and about 63,811 residents live in those ZIP codes (Census; not the number of people this system supplies). Approximately 52% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
Onalaska Waterworks's water is classified in EPA records as a groundwater source. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
Infrastructure Risk
PFAS in ZIP Codes This System Serves
PFAS ("forever chemicals") have been reported in samples from water systems associated with the ZIP codes in this system's area. These results can come from other water systems serving the same ZIP codes; check the UCMR5 section for any results reported for this system. 10 detections recorded. 2 detections are above the level of a federal PFAS MCL (4 ppt for PFOA and PFOS), with compliance required from 2029.
Comparable Water Systems
Similar-sized systems in Wisconsin
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
Onalaska Waterworks (EPA ID: WI6320327) is a community water system in Wisconsin that serves approximately 18,000 people from groundwater sources.
This system provides water to 4 ZIP codes across 4 communities.
ZIP-Area Home Safety Context: B (79/100)
This is the average Home Safety Score for 2 of 4 service-area ZIP codes with all required score domains observed. It is not a grade for the water utility.
Model 4.0.0 uses SDWIS identity plus accepted ECHO SDWA lifecycle-based water compliance, the UCMR 5 PFAS MCL screen, EPA radon zone, and annual EPA AirData AQI across three equally weighted domains. Missing required evidence suppresses the score.
Violation History
Lead & Copper
EPA Lead and Copper Rule evidence attributed directly to this water system:
| Lead Level | Exceeds Action Level | Sample Date |
|---|---|---|
| Below the reporting limit | No | 2023-09-30 |
No copper action-level exceedance record appears for this PWSID in the accepted LCR snapshot. This does not establish a clean copper measurement.
Radon Risk in Service Area
4 of 4 ZIP records with known zones are in EPA Radon Zone 2.
The EPA recommends testing all homes regardless of radon zone. County radon zones cannot replace an in-home radon test.
ZIP Codes Served
Coverage: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by WI or modeled from parcel and building-footprint data.
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View available EPA compliance records for Onalaska Waterworks (WI6320327) on EPA.gov.
Frequently Asked Questions
Is Onalaska Waterworks water safe to drink?
The accepted 2026Q2 ECHO snapshot contains zero violation records for Onalaska Waterworks in the inclusive 2021-2026 record-year window. This is a compliance-record finding, not a guarantee about water at a specific tap.
How many people does Onalaska Waterworks serve?
Onalaska Waterworks serves approximately 18,000 people across 4 ZIP codes in Wisconsin.
Where does Onalaska Waterworks get its water?
The primary water source is groundwater.
Federal UCMR5 PFAS Monitoring: Detected
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). PFAS compounds were detected; the table compares each one with the EPA MCL where one exists (April 2024 rule, compliance required from 2029) and with this state's enforceable standard where one exists.
EPA's April 2024 PFAS rule sets MCLs of 4 ppt for PFOA and PFOS and 10 ppt for PFHxS, PFNA and HFPO-DA (GenX); water systems must comply from 2029. Other PFAS compounds have no individual federal MCL. A state standard is shown only where this system's state has its own enforceable PFAS limit. Detection results are EPA UCMR5 samples, not a measurement at your tap.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Frequently Asked Questions
How to cite this page
ZipCheckup. (n.d.). Onalaska Waterworks, WI: Serves 18K People. https://zipcheckup.com/water-system/wi6320327/
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