Olympia Water Hardness & Quality Report (2026)

Olympia, Washington, the state capital and Thurston County seat at the southern tip of Puget Sound — the political heart of Washington State, home of Evergreen State College, and a major south Puget Sound trade and government center — draws its municipal water supply from the Squaxin Island aquifer zone, the Capitol Lake–Deschutes River watershed, and local Quaternary glacial outwash wells via the City of Olympia Public Works Utilities Water Division. Water hardness in Olympia measures 29.5 mg/L — classified as extremely soft.

Olympia's extraordinary softness reflects the south Puget Sound watershed's Olympic and Cascade Range volcanic and glacial geology. The Deschutes River (flowing into Capitol Lake) drains: the Black Hills (western Thurston County — Eocene Crescent Formation basalt — submarine basalt flows of the Olympic Peninsula terrane, extremely calcium-poor mafic rock); the Cascade Range foothills (Quaternary volcanic outwash from the Cascades — basalt and andesite-derived, calcium-poor); and the Puget Sound Lowland Quaternary glaciofluvial outwash (clean sand and gravel from the Vashon Glaciation — quartz-rich, minimal calcareous content). The dominant calcium-poor basalt and Quaternary quartz outwash terrain produces the extraordinary 29.5 mg/L at Olympia.

With hardness at 29.5 mg/L, Olympia residents experience essentially no scale challenges. City of Olympia Public Works Utilities Water Division consistently delivers water meeting all Washington DOE and EPA Safe Drinking Water Act requirements.