Board of Water Supply warns landfill over aquifer would threaten island's drinking water; council amends, advances resolution

The Board of Water Supply told the Honolulu City Council Environment Committee on Jan. 16 that siting a municipal landfill inland, above the volcanic aquifer, would risk permanent contamination of the island's drinking-water supply.

"Water is life," Ernie Lau, manager and chief engineer for the Board of Water Supply, said during a 30-slide briefing, arguing the board had formally disapproved the six inland sites proposed in 2022 and urging that new landfills be located in the coastal "caprock" zone where natural deposits offer greater protection for the freshwater lens beneath Oahu.

Lau told the committee that all of Oahu's municipal drinking water comes from underground aquifers and that rainfall and surface contamination eventually percolate through soil into those volcanic aquifers. He highlighted data showing landfill leachate can contain a broad mix of contaminants and noted that higher rainfall at some inland candidate sites could generate substantially greater volumes of leachate than the existing Waimanalo Gulch site.

"Preservation and protection of our precious, and pure groundwater resources are essential to ensure water security for our future, for generations to come," Lau said.

The committee then debated and amended Resolution 25-3, a reaffirmation of the council's 2003 policy that municipal solid-waste landfills should not be located "in proximity to any of the city's underground drinking…