Hermiston Water Hardness & Quality Report (2026)

The City of Hermiston, Oregon, operates a public water utility serving Morrow County in north-central Oregon. The system draws water from three primary deep wells tapping the Columbia River Basalt aquifer — the city's original and primary source — one shallow well, and a surface water intake from Lake Wallula on the Columbia River near McNary Dam. Water is treated via disinfection and filtration, with chlorine as the primary disinfectant, in compliance with Oregon Department of Environmental Quality (DEQ) and Oregon Health Authority standards.

Hermiston's water originates from the Columbia River Basalt Formation, a Miocene-age flood basalt sequence underlining much of eastern Oregon and Washington. This aquifer system naturally contains dissolved minerals — particularly calcium and magnesium — leached from the basaltic rock matrix. The shallow well and surface water from Lake Wallula add seasonal variability to the supply's mineral content. Eastern Oregon's semi-arid climate and basaltic and sedimentary geology result in a moderately to hard water supply typical of the region.

Residents may observe reduced soap lather, faint spotting on dishes and glassware, and gradual scale accumulation in water heaters and appliances. Dishwashers, washing machines, and hot water systems are most vulnerable to mineral buildup. Regular descaling and consideration of a water softener are recommended, particularly for households using hot water frequently. The City of Hermiston's 2023 Consumer Confidence Report confirms the utility meets all federal Maximum Contaminant Level Goals (MCLGs); nitrate levels are monitored due to agricultural activity and maintained well below the federal standard of 10 ppm. All treatment and monitoring comply with Oregon DEQ and Oregon Health Authority standards.