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. Committee members added a new whereas clause referencing Act 73 (2020), which restricts landfill siting in conservation districts and within a half‑mile of residences, schools and hospitals — a statutory constraint members said limits possible alternative sites on Oahu.

Board of Water Supply briefing: Lau explained that the island’s caprock — a less‑permeable coastal ring of sediments, coral and weathered volcanic rock — helps protect inland volcanic aquifers. He described how rainfall carries contaminants down through soil and that even well‑designed landfill liners will eventually fail without ongoing maintenance or liner replacement. Lau also highlighted recent PFAS testing and cited studies showing detectable per‑ and polyfluoroalkyl substances in landfill leachate; he noted a 30‑day administrative period triggered by his disapproval of a recently proposed site that he expected to end Jan. 16, 2025.

Administration response and options: Mike Formby, managing director for Honolulu City, told the committee the administration had evaluated three paths: safely citing a landfill over an aquifer using engineered containment, seeking legislative changes to widen siting options (Act 73), or pursuing a land‑use commission process to extend or modify use at the existing Waimanalo Gulch site. Formby pushed back on comparisons to the Navy’s Red Hill fuel leak, saying, “I don't think anybody should refer to our attempts to put a safe landfill over the aquifer as Red Hill 2. That is disingenuous.”

Roger Babcock, director of the Department of Environmental Services, said the city does not yet have a final cost estimate for building a replacement landfill and that earlier figures discussed in public testimony reflected uncertainty. “We really don't have a better number than $200,000,000 at this time,” Babcock said, adding that costs would depend heavily on land acquisition, design and other site‑specific factors. He also explained that refuse capital projects would be funded from the city’s general fund via general‑obligation bonds.

Committee action and amendment: Committee members amended Resolution 25‑3 to add a new whereas clause calling out Act 73 (2020), and the committee chair instructed that the resolution be reported out as CD1 for adoption. The committee recorded no objections during the voice‑vote procedure and advanced the amended resolution to full council for final action.

Public comment: Two remote and in‑person speakers addressed the briefing. Michael Gilbert, a resident of Aloha Beach, reminded the committee of previous operational failures at island waste facilities and said such histories argue for caution: “These systems do fail sometimes, especially due to extreme weather, human error, operational breakdowns.” Raquel Achoo of the North Shore urged more aggressive waste‑reduction measures and expressed concern that planning has not kept pace with risks to future generations.

What’s next: The committee advanced Resolution 25‑3, CD1, to full council. Lau noted that his disapproval of the proposed northwest Waihiwa site begins a 30‑day reconsideration period under BWS administrative rules; the board’s letter and the administration’s site‑selection process are likely to inform next steps, including the administration’s continued outreach with private landowners and the state legislature.