City of Ontario
EPA ID: OR4100587 · 14,465 people served · 2 ZIP codes
Tallying the federal enforcement file for City of Ontario yields 2 open violations that have not been formally closed — each finding sits in the EPA database while the utility continues to deliver water to approximately 14,465 residents and works through the required corrective action process.
Data: EPA SDWIS Last verified: 2026-04-02
Service Area Map
Coverage area for City of Ontario Source: EPA SDWIS service area boundaries.
Service area boundary — Grade B
Service Area Demographics
The City of Ontario serves a community with a median household income of $53,045 and an estimated 24,237 residents across its service area. Approximately 72% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
Environmental Justice Note: 100% of the population in this service area is classified as disadvantaged under EPA's EJScreen criteria. Communities with higher disadvantaged populations often face disproportionate environmental and health burdens, including aging water infrastructure and limited resources for remediation.
🌊 Where Does Your Water Come From?
City of Ontario's water is drawn from rivers, lakes, or reservoirs. Surface water sources are more exposed to agricultural runoff, stormwater, and upstream discharges, but they typically receive more intensive treatment before reaching your tap.
About 1% of homes in Malheur County, Oregon rely on private wells rather than public water systems. Private well owners are responsible for their own water testing and treatment.
Wastewater Proximity Note: This service area ranks in the 60th percentile nationally for proximity to wastewater discharge points. Surface water sources near wastewater outfalls may face additional treatment challenges.
Infrastructure Risk
Detected Contaminants
How City of Ontario compares to EPA limits
What This Means For You
Total Trihalomethanes (TTHM) at 1 mg/L exceeds the EPA maximum of 0.08 mg/L. Bladder & rectal cancer risk; reproductive concerns. Consider granular activated carbon (GAC) filtration.
Surface Water Treatment Rule at 3 mg/L exceeds the EPA maximum of mg/L.
Contaminant 3028 at 1 mg/L exceeds the EPA maximum of mg/L.
Consumer Confidence Report Rule at 1 mg/L exceeds the EPA maximum of mg/L.
E. coli at 1 Zero tolerance (any positive sample triggers immediate action) exceeds the EPA maximum of Zero tolerance (any positive sample triggers immediate action). Severe GI illness; potentially fatal kidney failure in children. Consider UV disinfection (99.99%) filtration.
Total Trihalomethanes (TTHM) was detected in this water system. granular activated carbon (GAC) filtration can reduce exposure.
Find a certified water filter →Comparable Water Systems
Similar-sized systems in Oregon
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
City of Ontario, (EPA ID: OR4100587) is a community water system in Oregon that serves approximately 14,465 people from surface water sources.
This system provides water to 2 ZIP codes across 2 communities.
Average Home Safety Score: B (70/100)
Based on water quality violations, lead levels, and radon risk across all ZIP codes served by this system.
Violation History
Recent Violations
| Date | Contaminant | Type | Status |
|---|---|---|---|
| July 1, 2025 | Surface Water Treatment Rule | Monitoring | Unresolved |
| October 1, 2024 | Total Trihalomethanes (TTHM) | Monitoring | Unresolved |
| October 1, 2024 | Surface Water Treatment Rule | Monitoring | Resolved |
| July 1, 2024 | Surface Water Treatment Rule | Monitoring | Resolved |
| January 1, 2024 | Contaminant 3028 | Monitoring | Resolved |
| January 1, 2024 | Total Trihalomethanes (TTHM) | Monitoring | Unresolved |
| October 1, 2023 | Surface Water Treatment Rule | Monitoring | Resolved |
| June 1, 2023 | Consumer Confidence Report Rule | Monitoring | Resolved |
| March 1, 2023 | E. coli | Monitoring | Resolved |
| March 1, 2023 | Fecal Coliform | Monitoring | Resolved |
| January 1, 2023 | Consumer Confidence Report Rule | Monitoring | Resolved |
Contaminants Detected
The following contaminants have been flagged in EPA records for this water system:
| Contaminant | Category | Violations | Health-Based |
|---|---|---|---|
| Surface Water Treatment Rule | Treatment Failure | 3 | No |
| Total Trihalomethanes (TTHM) | Disinfection Byproducts | 1 | No |
| Contaminant 3028 | Other Violation | 1 | No |
| Consumer Confidence Report Rule | Reporting Failure | 1 | No |
| E. coli | Microbiological | 1 | No |
| Fecal Coliform | Microbiological | 1 | No |
Lead & Copper
EPA Lead and Copper Rule sampling data for ZIP codes served by this system:
Radon Risk in Service Area
Dominant radon zone for ZIP codes served by this system: Zone 2 (Moderate Risk)
The EPA recommends testing homes in Zone 1 and Zone 2 areas for radon.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Let cold water run for 2 minutes before drinking — this helps flush lead from your pipes.
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 OR 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 the full compliance record for City of Ontario (OR4100587) on EPA.gov.
Frequently Asked Questions
Is City of Ontario water safe to drink?
City of Ontario has only monitoring/reporting violations, which are procedural in nature. The system meets federal health-based standards.
How many people does City of Ontario serve?
City of Ontario serves approximately 14,465 people across 2 ZIP codes in Oregon.
Where does City of Ontario get its water?
The primary water source is surface water.
Federal UCMR5 PFAS Monitoring: Tested Clean
This water system was tested under the federal EPA Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds were detected.
Current MCL reflects the lowest state-enforceable limit (NYS 10 ppt for PFOA/PFOS, effective August 2020). The federal final MCL of 4 ppt for PFOA/PFOS (EPA April 2024 rule) is not enforceable until April 2029. Detections above 4 ppt but below 10 ppt are below current MCL but above the future federal limit.
Source: U.S. EPA UCMR5 (Unregulated Contaminant Monitoring Rule, 5th cycle) — per-system federal sampling, 2023–2025. EPA UCMR5 monitoring program →
Lead Service Line Inventory
Service line breakdown reported under the federal Lead and Copper Rule Improvements (LCRI) inventory requirement:
This system reports zero confirmed lead service lines in its inventory. Unknown-material counts may still warrant verification.
Federal LCRI rule (effective October 2024) requires every public water system to inventory its service lines and complete lead-line replacement within 10 years.
Source: EPA SDWIS Federal Service Line Inventory (Phase 2) · Submitted 2026
ZipCheckup is not affiliated with the utility or state agency. Inventory figures render verbatim from the public LCRI submission cited above; ZipCheckup does not perform inspections or replacements.
How Water Systems Appear in Rankings
Water systems are evaluated by violation history, contaminant detections, and service population. Larger systems with more service connections appear in more rankings.
Frequently Asked Questions
What You Can Do
Test your water
Home test kits can detect lead, bacteria, and other contaminants at your tap. Find the right filter →
Check your specific ZIP code
Water quality can vary within a system. View nearest ZIP report →
Contact your utility
City of Ontario (EPA ID: OR4100587) — request the latest Consumer Confidence Report or ask about specific contaminants.