Oregon’s nitrate ground pollution became notably worse in past 10 years, report finds

By Ryan Haas | OPB | Jan. 23, 2025

The last time the Oregon Department of Environmental Quality compiled comprehensive data on nitrate ground pollution in the Lower Umatilla Basin was 2012. More than a decade later, Oregonians have their first fresh look at nitrate levels in the region, and it’s concerning.

The Department of Environmental Quality released an analysis of groundwater nitrate trends Wednesday for the Lower Umatilla Basin Groundwater Management Area, a stretch of around 550 square miles of farming communities in northern Morrow and northwest Umatilla counties.

Groundwater pollution from nitrates is a well-documented issue in that region, first acknowledged by the state in 1990. Since then, Oregon has struggled to control the seepage of nitrates — potentially carcinogenic compounds that can cause various other health issues — through groundwater into wells used for drinking water.

Wednesday’s report documents tests at 33 wells monitored by DEQ across the large geographic area. The majority of those wells are for domestic use, though two are used for irrigation purposes and one is used for commercial business.