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Tap water quality report

Lake Oswego, OR

EPA monitoring detected 14 contaminants across the 8 water suppliers serving Lake Oswego. A detection doesn't automatically mean the water is unsafe — see the highest level found for each below, with its EPA source and period.

8
water suppliers
48,025
people served
14
contaminants found
Oregon rankings Lead in Oregon PFAS in Oregon

What was found in Lake Oswego's water

The highest level seen across the city's suppliers, the EPA limit for each, and where the figure comes from.

ContaminantLevel vs EPA limitSuppliersSource
Nitrate
2600 µg/L 26%
of the EPA limit 10000 µg/L
 5/8 SYR4
Nitrate-Nitrite
2490 µg/L 25%
of the EPA limit 10000 µg/L
 3/8 SYR4
Copper
996 µg/L 77%
of the EPA limit 1300 µg/L
 8/8 SYR4
Lead
648 µg/L 4320%
of the EPA limit, in the worst sample — 15 µg/L
 5/8 SYR4
Fluoride
160 µg/L 4%
of the EPA limit 4000 µg/L
 4/8 SYR4
TTHM
59.4 µg/L 74%
of the EPA limit 80 µg/L
 3/8 SYR4
Total Haloacetic Acids (HAA5)
47.9 µg/L 80%
of the EPA limit 60 µg/L
 3/8 SYR4
Barium
43.9 µg/L 2.2%
of the EPA limit 2000 µg/L
 4/8 SYR4
Nitrite
18.5 µg/L 1.9%
of the EPA limit 1000 µg/L
 1/8 SYR4
Lithium
12 µg/L
No EPA limit set
 1/8 UCMR-5
Bromate
1.2 µg/L 12%
of the EPA limit 10 µg/L
 1/8 SYR4
Combined Radium (-226 And -228)
1.13 pCi/L 23%
of the EPA limit 5 pCi/L
 1/8 SYR4
Arsenic
0.7510 µg/L 7.5%
of the EPA limit 10 µg/L
 1/8 SYR4
Lead
0.0740 mg/L 493%
above the EPA limit of 0.0150 mg/L
 8/8 LCR
Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the single worst sample on record — over 100% is worth reading, but is not by itself a violation. Formal violations are listed separately. These are the utilities' own EPA-reported results, not a city-wide average. A detection means the lab measured the substance — it isn't the same as exceeding a legal limit. Hover a source tag to see the EPA program and years behind each figure.

Water suppliers serving Lake Oswego

SupplierPopulation 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, Lead, Fluoride. The full list, with the highest level found 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.