Ala Moana - Kaka'ako Water Hardness & Quality Report (2026)

Ala Moana-Kakaʻako, Hawaii, in Honolulu — a Honolulu neighborhood adjacent to Waikiki and Downtown Honolulu, centered on the Ala Moana Center (largest open-air shopping center in the United States) and the urban Kakaʻako waterfront — receives its municipal water from the Honolulu Board of Water Supply (BWS), drawing from the Oahu Basal Aquifer through production wells in the Honolulu-Pearl Harbor aquifer sector.

The soft 66 mg/L hardness and TDS of 207.9 mg/L reflect the Oahu Basal Aquifer's volcanic shield basalt character. The Oahu Basal Aquifer at the Honolulu sector consists of freshwater floating on saltwater within the Koolau Basalt (Pliocene-Pleistocene tholeiitic shield volcano lava — very low silica, primarily plagioclase-pyroxene basalt, nearly insoluble). The basal lens is recharged by rainfall on the Koolau and Waianae ranges. The moderate TDS (208 mg/L) relative to the low hardness (66 mg/L) reflects the presence of oceanic chloride from saltwater intrusion at the freshwater-saltwater interface in the Honolulu coastal basal lens.

At 66 mg/L, Ala Moana-Kakaʻako's water is soft — essentially no scale forms, soap lathers abundantly, and appliances maintain good efficiency. Annual descaling is sufficient. The PFAS level of 1.3 ppt is excellent — the lowest of any Honolulu neighborhood — reflecting the pure volcanic aquifer recharge and the limited PFAS industrial sources in the Koolau Range recharge zone above the Honolulu water supply wells.