Multnomah County, Oregon: drinking water report. Multnomah County – Portland – serves about 810,000 residents.
Multnomah County – Portland – serves about 810,000 residents. The Portland Water Bureau draws from the Bull Run Watershed, a 102-square-mile protected area in the Cascade Range east of the city. The watershed has been closed to public access since 1895, making it one of the longest-protected municipal water sources in the country. A secondary supply comes from the Columbia South Shore Well Field, drawing groundwater near the Columbia River.
Bull Run water is exceptionally clean – so clean that Portland operates under an EPA Surface Water Treatment Rule variance that has historically allowed the city to avoid filtration. However, the EPA revoked this variance and has required Portland to build a filtration plant, expected to be completed by 2030. The city has disputed the necessity, but compliance is proceeding.
UCMR5 data shows minimal PFAS detections in Portland's Bull Run supply. The Columbia South Shore Well Field, used as a backup, has more potential for PFAS contamination given its proximity to the Portland International Airport and industrial areas. According to the Oregon DEQ's 2024 data, PFAS was detected in the well field at levels below proposed federal MCLs. Oregon has adopted an advisory level of 30 ppt for the sum of five PFAS compounds.
Portland's Bull Run supply is among the cleanest in the country. The primary risk comes when the city switches to the Columbia South Shore backup supply during maintenance or drought.
Check your water to see current data for your area. For most Portland residents, filtration is optional but a carbon filter improves chlorine taste. Our water filter guide covers options. Pull your detailed report, and visit our Oregon page for statewide data.