Community Water System · PWS OR4100457
Lake Oswego Municipal Water
Operator location Lake Oswego, Oregon - larger served population (> 3,309) at 40,000 people served; 39 SDWIS violations on record from surface water sources.
- 40,000
- People served (this PWS)
- 39
- EPA violations (this PWS)
- 2
- Health-based (this PWS)
- No PFAS
- UCMR5 (this PWS)
Lake Oswego Municipal Water standing, mid SDWIS violation third
40,000 people served (SDWIS) - larger served population (> 3,309). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 5% is middle-third health share (≤ 23%). UCMR5: UCMR5 tested, none detected. Population rank #1,390 of 29,740 among systems serving 500+.
The verdict
Lake Oswego Municipal Water lands in the middle third by violation volume (39), large enough for peer comparisons without matching the fleet's heaviest ledgers. Population served is large (40,000; larger served population (> 3,309)), so household exposure scale sits behind the violation mix. Health-based share is 5% (middle-third health share (≤ 23%)). UCMR5 tested this system and reported no PFAS above the minimum reporting level.
- #1,390 of 29,740
- Population · /systems
- #17 of 373
- Population · OR
- 39
- Total EPA violations on record
- 5%
- Health-based (MCL / treatment failure)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
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 |
Violation Count vs. the National Corpus
Lake Oswego Municipal Water has 39 recorded EPA violations, 50% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 50% carry more. 5% of this system's own violations are health-based (2 of 39), and it ranks #1,390 of 29,740 by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
39 Lower than most fewer violations than 50% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
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 |
Population served record for Lake Oswego Municipal Water
EPA SDWIS lists 40,000 people served and 13,000 connections for this PWS, confirm the service-area footprint on the federal report before comparing to municipal census totals.
Sources: EPA SDWIS
Nationwide peers
39 violations · 40,000 served: nearest cross-state SDWIS matches.
Cross-state systems near this violation count
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
Cross-state systems with similar served population
Nearest cross-state systems by EPA SDWIS population_served (same 500+ sitemap gate).
What to do with Lake Oswego Municipal Water
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in Oregon compares on the same EPA violation measures. Oregon systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.