Community Water System · PWS OR4100457
Lake Oswego Municipal Water
Lake Oswego, Oregon 97035 - drinking water served from surface water sources to 40,000 people, tracked in EPA SDWIS and UCMR5.
- 40,000
- People served
- 39
- EPA violations
- 2
- Health-based
- No PFAS
- UCMR5 result
The verdict
EPA records 39 drinking-water violations at Lake Oswego Municipal Water, 5% of them health-based - below the Oregon per-system average.
- 39
- Total EPA violations on record
- 5%
- Health-based (MCL / treatment failure)
- 40,000
- People served by this system
- 0
- PFAS compounds detected (UCMR5)
Water Quality Snapshot: Lake Oswego Municipal Water
Lake Oswego Municipal Water is a local-owned community water system that delivers drinking water to 40,000 residents in Lake Oswego, Oregon (Clackamas County) through 13,000 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 39 total violations for this system , of which 2 (5%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 34 monitoring and reporting violations are on file. The most recent violation on record dates to 2025.
The most frequently cited contaminant at this system is Coliform (TCR), recorded in 6 violations (MR). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.
Across Oregon, EPA tracks 2,518 public water systems serving 4,005,242 people, with 206,659 cumulative violations and 20,339 health-based violations on record. About 99% of systems in the state carry at least one violation, and state-wide the average per system is 82.1 violations. Statewide, 30 of 125 UCMR5-tested systems have reported PFAS detections (24%).
Lake Oswego Municipal Water's 39 violations sit below the Oregon average.
All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.
System Details
- System Type
- Community
- Owner Type
- Local
- Connections
- 13,000
- County
- Clackamas
- School/Daycare
- No
- MCL Violations
- 0
- Monitoring Violations
- 34
- Treatment Tech Violations
- 2
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Coliform (TCR) | MR | 6 | 2009 |
| Nitrate | MR | 2 | 2008 |
| 2,4-D | MR | 2 | 2008 |
| Consumer Confidence Rule | Other | 2 | 2025 |
| Lead and Copper Rule | TT | 2 | 2000 |
| 1,2,4-Trichlorobenzene | MR | 1 | 2008 |
| cis-1,2-Dichloroethylene | MR | 1 | 2008 |
| Xylenes, Total | MR | 1 | 2008 |
| DICHLOROMETHANE | MR | 1 | 2008 |
| p-Dichlorobenzene | MR | 1 | 2008 |
| Vinyl chloride | MR | 1 | 2008 |
| Carbon tetrachloride | MR | 1 | 2008 |
| 1,1,2-Trichloroethane | MR | 1 | 2008 |
| Tetrachloroethylene | MR | 1 | 2008 |
| CHLOROBENZENE | MR | 1 | 2008 |
| Benzene | MR | 1 | 2008 |
| Toluene | MR | 1 | 2008 |
| Ethylbenzene | MR | 1 | 2008 |
| Styrene | MR | 1 | 2008 |
| Bromate | MR | 1 | 2019 |
| Gross Alpha, Excl. Radon and U | MR | 1 | 1976 |
| o-Dichlorobenzene | MR | 1 | 2008 |
| trans-1,2-Dichloroethylene | MR | 1 | 2008 |
| 1,2-Dichloroethane | MR | 1 | 2008 |
| 1,1,1-Trichloroethane | MR | 1 | 2008 |
| Combined Radium (-226 and -228) | MR | 1 | 1976 |
| 1,1-Dichloroethylene | MR | 1 | 2008 |
| Trichloroethylene | MR | 1 | 2008 |
| 1,2-Dichloropropane | MR | 1 | 2008 |
PFAS Testing Results (UCMR5)
Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 116 samples detected PFAS.
| Contaminant | Date | Result | MRL | Status |
|---|---|---|---|---|
| NFDHA | 7/31/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFOA | 7/31/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFHpS | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| NMeFOSAA | 7/31/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFBS | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFOS | 7/31/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFDA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDoA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFUnA | 7/31/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| 11Cl-PF3OUdS | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| 9Cl-PF3ONS | 7/31/2024 | <2.00 ppt | 2.00 ppt | Not Detected |
| PFTrDA | 7/31/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| PFNA | 7/31/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| NEtFOSAA | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| ADONA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFTA | 7/31/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFPeS | 7/31/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFEESA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMBA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMPA | 7/31/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| 8:2 FTS | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| 4:2 FTS | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 6:2 FTS | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFBA | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| HFPO-DA | 7/31/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFPeA | 7/31/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| HFPO-DA | 5/22/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFHxA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFTA | 5/22/2024 | <8.00 ppt | 8.00 ppt | Not Detected |
| PFTrDA | 5/22/2024 | <7.00 ppt | 7.00 ppt | Not Detected |
| NEtFOSAA | 5/22/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| NMeFOSAA | 5/22/2024 | <6.00 ppt | 6.00 ppt | Not Detected |
| PFBS | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHpA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFHxS | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFNA | 5/22/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOS | 5/22/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| PFOA | 5/22/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| 6:2 FTS | 5/22/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFDoA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| 8:2 FTS | 5/22/2024 | <5.00 ppt | 5.00 ppt | Not Detected |
| PFPeS | 5/22/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
| NFDHA | 5/22/2024 | <20.00 ppt | 20.00 ppt | Not Detected |
| PFEESA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMBA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFDA | 5/22/2024 | <3.00 ppt | 3.00 ppt | Not Detected |
| PFMPA | 5/22/2024 | <4.00 ppt | 4.00 ppt | Not Detected |
Verify This Water System
The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for Lake Oswego Municipal Water.
EPA SDWIS, Federal Reports
EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:
View PWS ID OR4100457 on SDWISSource: EPA SDWIS Federal Reports Search
Oregon Drinking Water Authority
Oregon's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.
Find OR regulator via EPA SDWISViolation Timeline
Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.
| Year (latest) | Contaminant | Category | Count | EPA Record |
|---|---|---|---|---|
| 2025 | Consumer Confidence Rule | Other | 2 | SDWIS / OR4100457 / 7000 |
| 2019 | Bromate | MR | 1 | SDWIS / OR4100457 / 1011 |
| 2009 | Coliform (TCR) | MR | 6 | SDWIS / OR4100457 / 3100 |
| 2008 | Nitrate | MR | 2 | SDWIS / OR4100457 / 1040 |
| 2008 | 2,4-D | MR | 2 | SDWIS / OR4100457 / 2105 |
| 2008 | 1,2,4-Trichlorobenzene | MR | 1 | SDWIS / OR4100457 / 2378 |
| 2008 | cis-1,2-Dichloroethylene | MR | 1 | SDWIS / OR4100457 / 2380 |
| 2008 | Xylenes, Total | MR | 1 | SDWIS / OR4100457 / 2955 |
| 2008 | DICHLOROMETHANE | MR | 1 | SDWIS / OR4100457 / 2964 |
| 2008 | p-Dichlorobenzene | MR | 1 | SDWIS / OR4100457 / 2969 |
| 2008 | Vinyl chloride | MR | 1 | SDWIS / OR4100457 / 2976 |
| 2008 | Carbon tetrachloride | MR | 1 | SDWIS / OR4100457 / 2982 |
| 2008 | 1,1,2-Trichloroethane | MR | 1 | SDWIS / OR4100457 / 2985 |
| 2008 | Tetrachloroethylene | MR | 1 | SDWIS / OR4100457 / 2987 |
| 2008 | CHLOROBENZENE | MR | 1 | SDWIS / OR4100457 / 2989 |
How Lake Oswego Municipal Water Compares
Cross-reference this system's record against state averages and the federal MCL framework for context.
| Metric | Lake Oswego Municipal Water | Oregon avg | Federal benchmark |
|---|---|---|---|
| Total violations | 39 | 82.1 | SDWA compliance, any non-zero count is a recorded breach |
| Health-based violations | 2 | 8.1 | Indicates a contaminant exceeded a federal MCL |
| PFAS detection | None | 24% | EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt |
| Population served | 40,000 | 1,591 | Sizing context for compliance burden |
Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 2,518 regulated public water systems in Oregon.
Federal MCL reference, Safe Drinking Water Act thresholds ▼
| Contaminant | Federal MCL / Action Level | Note |
|---|---|---|
| Lead | 0 mg/L (Action Level: 0.015 mg/L) | Lead and Copper Rule treatment technique |
| Arsenic | 0.010 mg/L (10 ppb) | Health-based MCL since 2006 |
| Total Coliform | Treatment technique (RTCR) | Indicator organism, monitoring trigger |
| PFOA / PFOS (PFAS) | 4.0 ppt each (final 2024 rule) | Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026) |
| Nitrate (as N) | 10 mg/L | Acute health risk for infants |
Frequently Asked Questions
Is Lake Oswego Municipal Water water safe to drink? ▼
How many people does Lake Oswego Municipal Water serve? ▼
What type of violations does Lake Oswego Municipal Water have? ▼
Has PFAS been detected in Lake Oswego Municipal Water water? ▼
What water source does Lake Oswego Municipal Water use? ▼
Where does this data come from? ▼
Read our methodology - how this data is sourced, computed, and verified.
Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.