Board of Water Supply warns proposed landfill site could threaten Oahu groundwater; committee reaffirms policy to avoid aquifer proximity

The Honolulu Board of Water Supply told the City Council committee on Jan. 14 that a proposed new municipal landfill site northwest of Waihiwa sits above a volcanic groundwater aquifer and could pose long-term contamination risks if leachate escapes containment.

In an informational briefing to the Council’s Committee on Housing, Sustainability, Economy and Health, Ernie Lau, manager and chief engineer for the Board of Water Supply (BWS), said Oahu is “100 percent dependent on groundwater aquifer” for drinking water and that “landfills contain contaminants that can enter groundwater.” Lau said the board previously reviewed six candidate sites submitted by the Department of Environmental Services in November 2022 and formally disapproved those locations because they lie inland of the island’s protective coastal caprock.

Why it matters: The committee took the briefing into account before amending and advancing Resolution 25‑3, which reaffirms the city policy adopted in 2003 that a municipal solid‑waste landfill should not be located in proximity to the city’s underground drinking‑water resources.…