What was found in Lake Oswego's water
The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.
| Contaminant | Level vs EPA limit | Suppliers | Source |
|---|---|---|---|
| Nitrate | 2490 µg/L 25% of the EPA limit 10000 µg/L Highest in the city: RIVERGROVE WATER DISTRICT · 4,000 people · 2019 | 5/8 | SYR4 |
| Nitrate-Nitrite | 2401.5 µg/L 24% of the EPA limit 10000 µg/L Highest in the city: RIVERGROVE WATER DISTRICT · 4,000 people · 2019 | 3/8 | SYR4 |
| Copper | 70.7 µg/L 5.4% of the EPA limit 1300 µg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2017
Highest in the city: 778.75 µg/L — RIVERGROVE WATER DISTRICT · 4,000 people · 2019 | 8/8 | SYR4 |
| Fluoride | 160 µg/L 4% of the EPA limit 4000 µg/L Highest in the city: GLENMORRIE COOPERATIVE ASSN · 310 people · 2019 | 4/8 | SYR4 |
| TTHM | 43.43 µg/L 54% of the EPA limit 80 µg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2019
Highest in the city: 49.51 µg/L — LAKE GROVE WATER DISTRICT · 3,100 people · 2019 | 3/8 | SYR4 |
| Barium | 43.9 µg/L 2.2% of the EPA limit 2000 µg/L Highest in the city: EXCALIBUR VILLAGE · 180 people · 2019 | 4/8 | SYR4 |
| Total Haloacetic Acids (HAA5) | 39.69 µg/L 66% of the EPA limit 60 µg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2019
Highest in the city: 41.52 µg/L — LAKE GROVE WATER DISTRICT · 3,100 people · 2019 | 3/8 | SYR4 |
| Lead | 12.2 µg/L 81% of the EPA limit 15 µg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2017
Highest in the city: 23.25 µg/L — LAKE GROVE WATER DISTRICT · 3,100 people · 2019 | 5/8 | SYR4 |
| Nitrite | 18.475 µg/L 1.8% of the EPA limit 1000 µg/L Highest in the city: GLENMORRIE COOPERATIVE ASSN · 310 people · 2019 | 1/8 | SYR4 |
| Lithium | 12 µg/L No EPA limit set Highest in the city: RIVERGROVE WATER DISTRICT · 4,000 people · 2025 | 1/8 | UCMR-5 |
| Bromate | 1.2 µg/L 12% of the EPA limit 10 µg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2019 | 1/8 | SYR4 |
| Combined Radium (-226 And -228) | 1.13 pCi/L 23% of the EPA limit 5 pCi/L Highest in the city: CARVER MOBILE RANCH · 110 people · 2019 | 1/8 | SYR4 |
| Arsenic | 0.7510 µg/L 7.5% of the EPA limit 10 µg/L Highest in the city: CARVER MOBILE RANCH · 110 people · 2018 | 1/8 | SYR4 |
| Lead | 0.0 mg/L 0% of the EPA limit 0.0150 mg/L Main supplier: LAKE OSWEGO MUNICIPAL WATER · 40,000 people · 2023
Highest in the city: 0.0740 mg/L — CARVER MOBILE RANCH · 110 people · 2025 | 8/8 | LCR |
Water suppliers serving Lake Oswego
| Supplier | Population served |
|---|---|
| LAKE OSWEGO MUNICIPAL WATER | 40,000 |
| RIVERGROVE WATER DISTRICT | 4,000 |
| LAKE GROVE WATER DISTRICT | 3,100 |
| GLENMORRIE COOPERATIVE ASSN | 310 |
| SKYLANDS WATER COMPANY | 250 |
| EXCALIBUR VILLAGE | 180 |
| CARVER MOBILE RANCH | 110 |
| ASHDOWN WOOD WATER COMPANY | 75 |
Frequently asked questions about Lake Oswego tap water
Is Lake Oswego tap water safe to drink?
EPA testing detected 14 contaminants in the water serving Lake Oswego. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.
How many water suppliers serve Lake Oswego?
8 public water suppliers report drinking-water monitoring for Lake Oswego, Oregon to the EPA. Each is listed above with its population served.
What contaminants are in Lake Oswego's water?
The contaminants EPA monitoring detected in Lake Oswego include Nitrate, Nitrate-Nitrite, Copper, Fluoride, TTHM. The full list, with the level at the main supplier and the data source, is in the table above.
Where does this data come from?
Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.