Union Hill-Novelty Hill Water Hardness & Quality Report (2026)

Union Hill Water Association (UHWA), serving the Union Hill-Novelty Hill community in unincorporated King County near Sammamish, Washington (mailing address 1510 228th Ave SE, Sammamish, WA 98075), provides groundwater to approximately 1,500 connections. The utility sources water from local wells tapping glacial aquifers on the Sammamish Plateau. No specific treatment plants are named; the system avoids adding disinfectants or fluoride, relying on natural groundwater quality with minimal processing, using hypochlorite if needed alongside filtration per some reports. UHWA reports very good water quality meeting EPA standards and emphasizes pristine source protection.

The Sammamish Plateau watershed drains into the broader Sammamish River and Lake Sammamish basin within the Puget Lowland. Glacial deposits from the Pleistocene Vashon Glaciation dominate, including permeable outwash gravels and sands of the Vashon Aquifer overlain by till. These unconsolidated sediments, derived from Cascade Range volcanics and Olympic metamorphic rocks, release calcium and magnesium ions during infiltration, producing moderately mineralised groundwater that avoids both the softness of direct rainfall and the hardness of deep limestone karst.

Moderately hard water leaves minor scale on fixtures and appliances like dishwashers, washing machines, and water heaters, but rarely causes severe buildup or efficiency losses. Soap lathering may be slightly reduced and glassware may spot. Routine maintenance includes periodic descaling of faucets and heaters; a water softener is optional rather than essential at this hardness level. Rinse aids help mitigate spotting. Groundwater typically runs near neutral pH with low corrosivity, and no fluoride is added.