Bayside Water Hardness & Quality Report (2026)

Bayside, California, in Humboldt County — an unincorporated Humboldt County community adjacent to Eureka and Arcata on Humboldt Bay in northwest California — receives its municipal water from the Humboldt Bay Municipal Water District (HBMWD), drawing from the Mad River (Humboldt County) through the Ruth Reservoir and district treatment system.

The moderately hard 150.5 mg/L hardness and elevated TDS of 439.3 mg/L are significantly harder than expected for coastal north California (far harder than other northern California supplies), suggesting a notable calcareous contribution from the Klamath Mountains geology. The Mad River drains the Klamath Mountains — Jurassic Franciscan Complex (insoluble mafic melange — usually soft), but also the Cretaceous Yager Formation (calcareous marine mudstone-sandstone — the primary hardness source in the Mad River watershed), and Cretaceous King Range terrane calcareous units.

At 150.5 mg/L, Bayside's water is moderately hard — scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling is appropriate. The PFAS level of 6.5 ppt warrants a certified drinking water filter — Naval Air Station Lemoore (distant, but central California PFAS drainage), the Humboldt County timber industry PFAS legacy, and the northwest California coastal PFAS background contribute to Bayside's readings.