Snohomish County, Washington: drinking water report. Snohomish County sits north of Seattle, home to about 830,000 residents.
Snohomish County sits north of Seattle, home to about 830,000 residents. Everett, the county seat, draws from the Sultan River through the Spada Lake reservoir – a protected watershed that produces exceptionally clean source water. Other communities purchase wholesale from Everett, from Seattle's system, or operate independent well systems drawing from glacial aquifers.
Everett's Sultan River source is one of the cleanest municipal water supplies in the Pacific Northwest, requiring minimal treatment. The protected watershed model keeps contaminant levels well below federal limits for most parameters.
PFAS is the exception to the generally positive picture. Paine Field (Snohomish County Airport) in Everett has documented AFFF use, and the former Naval Station Everett (now partially transferred to the Port of Everett) is another potential PFAS source. According to the Washington Department of Ecology, PFAS has been detected in groundwater monitoring wells near both facilities. UCMR5 data shows detections in four public water systems countywide.
Most Snohomish County residents on the Everett system enjoy high-quality water. Groundwater-dependent communities and those near Paine Field face more variable conditions.
Check your water to confirm your source and see current data. For PFAS near known sources, activated carbon or RO filters provide household protection. Our water filter guide details which certifications matter. Pull your detailed report, and visit our Washington page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Snohomish County, WA.
The EPA places Snohomish County, WA in Zone 3 - the EPA's lowest-risk category, with a predicted average indoor radon level below 2 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
37% of homes in Snohomish County, WA were built before 1980, and 7% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Snohomish County, WA averages 9.3 µg/m³, above the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide
Across 78 public water systems serving Snohomish County, WA with EPA lead testing on record, 1 (1.3%) reported a 90th-percentile lead result above the EPA's 15 ppb action level, and the median is 2.6 ppb. 5 water systems serving Snohomish County, WA carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Revised Total Coliform Rule | 3 |
| Lead and Copper Rule | 1 |
| Lead and Copper Rule Revisions | 1 |
| Haloacetic Acids (HAA5) | 1 |
| Arsenic | 1 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.