By Gosia Wozniacka | The Oregonian/OregonLive | Jan. 28, 2025

Nitrate pollution has worsened significantly in eastern Oregon over the past decade, according to a new analysis released by the Oregon Department of Environmental Quality.

The report is the first comprehensive data analysis since 2012 of nitrate pollution in groundwater in the Lower Umatilla Basin Groundwater Management Area. The area covers about 550 square miles in northern Morrow and northwestern Umatilla counties and supplies drinking water to thousands of residents, mostly through domestic wells.

The increase in pollution is notable because until recently many people in the region had no idea they had been drinking contaminated water for years – and some still don’t know because the state has yet to test all of the area’s domestic wells. The monitoring groundwater well network has been sampled for over three decades after the state first learned of the contamination in 1990.

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