Honolulu plans to seek state approval to expand the Waimanalo Gulch Sanitary Landfill in Kapolei, potentially adding nearly 92.5 acres to the island’s main municipal dump and extending its operational lifespan. The proposal comes amid ongoing political debates over finding a new landfill site and faces new state rules that restrict where landfills can be located. Neighbors and water officials say the plan could reignite concerns about groundwater protection and the long-term costs of Oʻahu’s waste management strategy.
What the city is proposing
City officials plan to request a special-use permit to expand the roughly 200-acre Waimanalo Gulch Sanitary Landfill by about 92.5 acres, a process requiring multiple levels of state and city approval. The administration says the expansion would allow the city to maintain flexibility while continuing to explore long-term waste management options for Oʻahu.
Environmental review underway
The City Department of Environmental Services says that any expansion of the landfill would require a formal environmental review and detailed technical studies, according to planning documents from the City of Honolulu. The materials also note that diversion programs, including recycling and H-POWER ash management, have already reduced the volume of waste sent to the landfill, and officials plan to consider these efforts in the environmental review.
Public meeting set for Jan. 13
The city has scheduled a public information meeting on Jan. 13 at the Kalanianaʻole Beach Park multipurpose room in Waiʻanae to present the proposal and answer questions from residents. The meeting notice is listed in the city’s official public postings at State Legals.
Water-supply alarm from the Board of Water Supply
Honolulu’s Board of Water Supply has repeatedly warned that building new landfills or expanding existing ones near Oʻahu’s aquifer could risk contaminating the island’s drinking water with chemically tainted leachate. Manager Ernie Lau told Hawaii News Now that even modern containment systems can fail over time, and any leaks could travel slowly underground, taking years to be detected—an argument central to opponents of the plan.
New law narrows siting options
In 2024, the Legislature passed HB 969, signed as Act 255, which prohibits the construction, modification, or expansion of any waste facility on land located near or above a significant aquifer, as defined by the Department of Health. The law is among several policy changes that will influence the review of any permit application and limits where Honolulu can site long-term waste infrastructure. The bill’s status and full text are available through legislative tracking resources such as Civil Beat.
Where the city looked before
From 2023 to 2025, the administration surveyed alternative landfill sites and in December 2024 briefly proposed a location on Dole Food Co.-owned agricultural land near Wahiawā, a plan that quickly faced strong community and legislative opposition. Reporting from Hawaiʻi Public Radio highlighted concerns over the protection of the underlying aquifer and long-term risks to drinking water.
Deadlines, capacity and next steps
The state Land Use Commission has directed Waimanalo Gulch to stop accepting new trash by March 2028, though city planners say the landfill would not reach full capacity until about 2032 if its current footprint remains unchanged. The accelerated timeline leaves Honolulu considering whether to pursue a special-use permit and environmental review, request a deadline extension, or continue searching for a replacement site, each option presenting its own political and legal challenges.
Recent compliance work at the site
Following previous stormwater and compliance issues, federal and state regulators required upgrades at Waimanalo Gulch, which the U.S. Environmental Protection Agency later confirmed were completed by the city and the landfill’s operator under a 2019 consent decree. The EPA’s documentation of these improvements is expected to be included in the technical record if an expansion request proceeds.
The next key steps are the Jan. 13 community meeting and the launch of the environmental review process, which will provide the public with its first look at detailed engineering plans and the city’s analysis of trade-offs. The process is expected to draw strong public testimony, scrutiny from water regulators, and renewed debate in the Legislature as Honolulu revisits a longstanding landfill challenge.
