State Well Water Guide
Oregon Private Well Water Guide
Approximately 27% of Oregon residents — about 1.1 million people — rely on private wells. Oregon's well water risks vary dramatically by region: western Oregon's high rainfall creates bacterial and nitrate risks from agricultural runoff, while eastern Oregon's basalt geology contributes naturally occurring arsenic and uranium. The Willamette Valley — Oregon's most populated agricultural region — has documented nitrate contamination in shallow wells. PFAS plumes have been identified near several military and industrial sites. The Oregon Health Authority oversees well construction but not ongoing private well testing.
Testing Guidance
The Oregon Health Authority recommends annual bacteria and nitrate testing for all private wells. Arsenic testing is particularly important for wells in eastern Oregon's basalt formations and south-central Oregon. PFAS testing is recommended for wells near Kingsley Field (Klamath Falls), Camp Rilea, and Salem-area industrial sites. Willamette Valley wells near vineyards, orchards, or nurseries should be tested for pesticides. Post-flood testing is critical given western Oregon's heavy rainfall patterns.
What to Test For in Oregon
Total coliform bacteria and E. coli — annual minimum for all wells
Nitrates — annual for Willamette Valley agricultural wells and wells near septic systems
Arsenic — all eastern Oregon wells, particularly in Harney, Malheur, and Lake counties
Uranium — basalt and volcanic geology areas in central and eastern Oregon
PFAS — wells near Kingsley Field, Camp Rilea, and industrial areas in the Willamette Valley
Pesticides — agricultural areas, especially Willamette Valley nursery and orchard regions
Iron and manganese — coastal and Willamette Valley wells
Common Contamination Risks in Oregon
Nitrate contamination in Willamette Valley shallow wells from agricultural fertilizers and septic systems
Naturally occurring arsenic in eastern Oregon's basalt and volcanic rock formations
Bacterial contamination following heavy rainfall events — particularly in shallow wells in western Oregon
PFAS plumes from military installations (Kingsley Field) and historical industrial operations
Pesticide residues near intensive horticultural operations in the Willamette Valley
Contaminant Guides Relevant to OR Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
pH
Water Quality Indicators
EPA limit: 6.5–8.5 (secondary standard)
Find a Certified Lab in Oregon
Use the Oregon state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
OR Certified Lab Directory ↗Oregon Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
OR Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
OR Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides