Washington County, Oregon: drinking water report. Washington County west of Portland has about 601,000 residents in communities including Hillsboro,…
Washington County west of Portland has about 601,000 residents in communities including Hillsboro, Beaverton, and Tigard. The Tualatin Valley Water District and Joint Water Commission draw from the Tualatin River basin and Bull Run Watershed (Portland's supply). The county is the heart of Oregon's Silicon Forest – Intel's largest manufacturing complex in the U.S. is here – and the semiconductor industry's water use and chemical handling create a specific water quality context.
Semiconductor manufacturing uses large quantities of ultrapure water and a range of chemicals including PFAS-containing surfactants. According to Oregon DEQ's 2024 investigation, PFAS detections in Washington County water systems have been linked to both industrial sources (Intel and other chipmakers) and the Hillsboro Airport's AFFF use. Monitoring wells near the airport show PFOS at 14 ppt.
The Tualatin River itself receives treated wastewater from the Clean Water Services regional system. A 2024 DEQ river assessment found that the Tualatin shows elevated pharmaceuticals and personal care products downstream of wastewater outfalls – compounds that conventional treatment partially removes but does not eliminate.
Washington County benefits from access to Portland's Bull Run supply – one of the cleanest surface water sources serving any major metro. Residents on the Tualatin River supply receive well-treated water, but the river's urban and industrial inputs warrant household attention.
Check your water for current data. For the industrial and emerging contaminants in this area, reverse osmosis at the kitchen tap provides comprehensive protection. Our water filter guide covers systems suited to Pacific Northwest water. Pull your detailed report for local data, and visit our Oregon page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Washington County, OR.
The EPA places Washington County, OR in Zone 2 - a moderate-risk category, with a predicted average indoor radon level between 2 and 4 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 Washington County, OR were built before 1980, and 5% 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 Washington County, OR averages 8.6 µg/m³, within 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