Aliamanu / Salt Lakes / Foster Village Water Hardness & Quality Report (2026)

Aliamanu–Salt Lake–Foster Village, Hawaii, a census-designated community in Honolulu County on the island of Oahu — a densely populated central Honolulu community adjacent to Pearl Harbor, home of Tripler Army Medical Center (the Pacific Region's primary US Army medical center — one of the most distinctive red buildings in Hawaii), the Salt Lake residential neighborhood, and a heavily military-connected and diverse Honolulu community between Pearl Harbor and the urban core of Honolulu — draws its municipal water supply from the Pearl Harbor Aquifer via the Honolulu Board of Water Supply (BWS). Water hardness in Aliamanu–Salt Lake–Foster Village measures 35 mg/L — classified as very soft.

Aliamanu–Salt Lake–Foster Village's very soft supply reflects the central Oahu basaltic volcanic aquifer's calcareous-poor geology. The Pearl Harbor Aquifer draws from: the Ko'olau Basalt (Pleistocene tholeiitic basalt of the Ko'olau Volcano — calcareous-poor Fe-Mg silicate basalt with minimal carbonate content); the Wai'anae Volcanics (Pliocene–Pleistocene calcareous-poor basalt of the older Wai'anae Volcano). The Hawaiian basaltic volcanic aquifer system produces inherently soft water throughout Oahu. BWS treatment of the calcareous-poor Ko'olau basalt aquifer produces the very soft 35 mg/L.

With hardness at 35 mg/L, Aliamanu–Salt Lake–Foster Village residents enjoy very soft water. BWS consistently delivers water meeting all Hawaii DOH and EPA Safe Drinking Water Act requirements.