Department of Environmental Services

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Refuse Division

Proposed Landfill Siting

The City is moving forward with Makaiwa Hills as
the proposed site for a new landfill on Oʻahu

Aerial map of West Oʻahu showing the Waimānalo Gulch Sanitary Landfill and the proposed Makaiwa Hills landfill expansion to the northeast, with a proposed access road connecting the site to Farrington Highway. Nearby communities labeled include Ko Olina, Honokai Hale, and Makakilo.
Map of proposed landfill and access road with surrounding areas.

The City and County of Honolulu Department of Environmental Services has identified Makaiwa Hills as the only possible location for Oʻahu’s future municipal solid waste landfill, marking a major step in securing long-term waste disposal needs for the island as the available space at the current Waimānalo Gulch Sanitary Landfill nears capacity.

Why Makaiwa Hills

The decision follows a multi-year evaluation process involving technical studies, environmental review, legal changes and land-use constraints that significantly narrowed the number of viable locations available on Oʻahu to ultimately just this one.

The City has been working since 2021 to identify a future landfill site through a comprehensive process that included input from technical experts, engineering consultants and community stakeholders.

In 2022, ENV launched a formal siting study with a Landfill Advisory Committee (LAC) and led to the City naming a site northwest of Wahiawā on Dole lands as a leading option in December 2024. But following the passage of Act 255 during the 2025 Legislative Session, that site was removed from consideration due to new restrictions prohibiting landfills on Class A agricultural lands and above sources of drinking water.

After applying all current restrictions and technical criteria, Makaiwa Hills emerged as the only remaining feasible option for a future landfill on Oʻahu.

A Difficult but Necessary Decision

City officials acknowledged the significance of the decision and the responsibility that comes with it.

Even with continued investment in recycling, composting and waste-to-energy, a landfill remains necessary for materials that cannot be recycled or combusted, including ash and other non-recoverable materials.

Next Steps

The City is currently moving forward with the required planning, environmental review, permitting and community engagement process for the Makaiwa Hills site. Additional opportunities for public input will be announced as the project advances.

The City remains committed to transparency and responsible planning to fulfill its kuleana to protect public health, protect our precious environment and provide reliable waste management for Oʻahu.

Learn more: The History of Oʻahu's Landfill
Landfill Siting Study & Landfill Advisory Commitee recommendations
Landfill Siting Study Supplemental Technical Memorandum

Click on the interactive map to view the restricted areas

When identifying potential landfill sites, ENV considered restrictions established by Act 73 and other state regulations.

Interactive map of Oʻahu showing areas with landfill siting restrictions. Different colored zones represent various environmental, land use, and regulatory constraints, with remaining uncolored areas indicating where a future landfill could potentially be located.

Interactive map of Oʻahu showing areas with landfill siting restrictions. Different colored zones represent various environmental, land use, and regulatory constraints, with remaining uncolored areas indicating where a future landfill could potentially be located.Act 73 Restrictions

Act 73, which became law on Sept. 15, 2020, states in part that:

1) No waste or disposal facility shall be located in a conservation district except in emergency circumstances where it may be necessary to mitigate significant risks to public safety and health; provided further that emergency circumstances shall not exceed three years.

and,

2) No person, including the state or any county, shall construct, modify or expand a waste or disposal facility including a municipal solid waste landfill unit, any component of a municipal solid waste landfill unit, a construction or demolition landfill unit, or any component of a construction and demolition landfill unit without first establishing a buffer zone of no less than one-half mile around the waste or disposal facility.

These restrictions are depicted in the green and blue layers, respectively. In consideration of the new restrictions imposed by Act 73, the results of all previous landfill siting evaluations are being thoroughly re-evaluated.

Other Restrictions

  • Airport Buffer – State of Hawai‘i Solid Waste Management Rules require a buffer from a municipal solid waste disposal facility of 10,000 feet of any airport runway used by turbojet aircraft and 5,000 feet for piston-type aircraft.
  • Tsunami Evacuation Zone – State of Hawai’i Solid Waste Management Guidelines discourage siting of a municipal solid waste disposal facility in possible tsunami inundation areas.
  • Developed and Undevelopable Lands – Land that has existing commercial, industrial, and other use, or land on which future development is planned. Other use development includes, but is not limited to, photovoltaic solar and wind farm renewable energy projects.
  • Federal Lands – Federal lands consist of United States Department of Defense managed land and other federally owned land that would limit use of the land from development of a municipal solid waste disposal facility.
  • Waimānalo Gulch Sanitary Landfill (“WGSL”) – The city’s current municipal solid waste landfill, which started operations in 1987. The site currently takes approximately 90,000 tons of special waste and municipal solid waste and 165,000 tons of ash and residue from H-POWER per year. Per the state of Hawai’i Land Use Commission (LUC), a new landfill site was to be named by Dec. 31, 2022. Following a formal request by the city, the LUC granted an extension to identify an alternative landfill site by Dec. 31, 2024. Waimānalo Gulch Sanitary Landfill must cease operations by March 2, 2028.

In 2021, the mayor appointed a Landfill Advisory Committee (“LAC”) to evaluate potential landfill sites using a set of diverse criteria. The result of the LAC process (2021-2022), including the site scoring and ranking and LAC recommendations, is detailed in the Oʻahu Landfill Siting Study & Landfill Advisory Committee Recommendations, Final Report. The LAC included members with different backgrounds (see right) including government, commercial, and non-governmental organizations.

LAC Meetings

The LAC met eight times, following a set of rules, as proposed by ENV and adopted by the LAC at LAC Meeting 2 Oct. 25, 2021, to facilitate its efforts. The details and documents associated with those meetings are described below.

The eighth LAC meeting occurred June 6, 2022, at 2:00 p.m. in-person at Kapolei Hale and online on interactive conference technology.

LAC Meeting 8 Documents

Written Comments

Meeting Record

The seventh LAC meeting is occured April 4, 2022, at 2:00 p.m. The meeting was an in-person meeting held at Kapolei Hale, Conference Room “A”. Registration for public comments was conducted onsite on the day of the meeting. See the agenda for more details.

LAC Meeting 7 Documents

Written Comments

Meeting Record

The sixth LAC meeting occurred March 7, 2022, at 2:00 p.m. See below for the related documents and recording.

LAC Meeting 6 Documents

Written Comments

Meeting Record

The fifth LAC meeting was held February 7, 2022, at 2:00 p.m., on the Webex videoconferencing platform.

LAC Meeting 5 Documents

Written Comments

Meeting Record

The fourth LAC Meeting was held December 14, 2021, at 10:00 a.m. The meeting occurred virtually through the Webex videoconferencing platform. The agenda for the meeting and supplementary documents are below.

Meeting Record

A limited meeting for the LAC was held November 3, 2021, at 1:00 p.m. The meeting was a tour of PVT Landfill, Waimänalo Gulch Sanitary Landfill, and H-POWER. The limited meeting was not open to the public due to danger to health and safety at the facilities and the impracticability of maintaining safe practices and social distancing requirements in place due to concerns with COVID-19 and its variants. Seven of the nine LAC members attended. The meeting agenda and meeting record are below.

Meeting Record

The meeting was recorded and the three parts are listed below. The meeting went into recess upon LAC motion between the starting point at Kapolei Hale and PVT Landfill and between each of the facility visits. Due to the camera overheating toward the end of the WGSL portion, only audio is available for a short section.

A special meeting for the LAC was held October 25, 2021, at 2:00 p.m. The meeting occurred virtually through the Webex videoconferencing platform. The agenda for the meeting and the supplementary document are below.

Meeting Record

No public comments were received in relation to LAC Meeting 2.

The first LAC Meeting was held October 4, 2021, at 2:00 p.m. The meeting occurred virtually through the Webex videoconferencing platform. The agenda and supplementary documents are provided below for reference in relation to the meeting.

Meeting Record

Public Comments Received

Letter to Landfill Advisory Committee from Senator Kurt Fevella, received October 4, 2021, at 12:56 p.m.

Landfill Advisory Committee

Brennon Morioka
Professional Engineer – Civil Engineering

Cynthia Rezentes
Classical Electrical Engineering/Community Advocate

Emmett Kinney
General Contracting

James Nakatani
Agribusiness Development

Ken Kawahara
Professional Engineer – Civil Engineering

Steven Chang
Environmental Regulation

Suzanne Jones
Solid Waste

Trisha Kehaulani Watson
Environmental Justice/Cultural Resources

  1. Does the current landfill at Waimānalo Gulch Sanitary Landfill (WGSL) have capacity beyond 2028?

Current projections show that the landfill could continue to receive waste through approximately 2031 within the permitted landfill area, based on annual fill-rate projections and remaining volume estimates. However, a 2019 Land Use Commission (LUC) decision and order requires WGSL to close and no longer receive waste after March 2, 2028. The Department of Environmental Services (ENV) is currently working to extend that deadline while a landfill expansion is developed.

  1. Why does the new landfill have to be in West Oʻahu when the Mayor promised it wouldn’t be? What happened to the proposed landfill near Wahiawa?

This proposed site is not a new landfill, but an adjacent expansion of WGSL. It will operate as part of the current landfill system rather than as a new standalone facility. The expansion will be on the Makaiwa property adjacent to the existing WGSL, and accessed from the current entrance and scalehouse by a new access road, minimizing impacts to the surrounding community and avoiding large trucks driving through residential streets.

  1. What will this landfill be called?

The landfill expansion will continue to operate as part of the Waimānalo Gulch Sanitary Landfill system. The naming convention will be determined at a later date.

  1. Is it possible to ship Oʻahu’s waste to another location?

Yes, but it is not a viable long-term solution due to cost, logistics, environmental permitting and port availability. In 2008, the City explored shipping 100,000 tons of waste per year from Oʻahu to a mainland landfill in Oregon at a cost of $99.83 per ton, plus tax and fuel, totaling roughly $10 million annually at that time. Costs are estimated to be at least double that amount today.

Currently, approximately 225,000 tons of municipal solid waste (MSW), H-POWER ash and other non-combustible, non-recyclable and special waste materials are disposed of at WGSL each year. Due to expense and operational risk, shipping waste off-island is not considered a sustainable long-term option.

  1. Approximately, how many tons of municipal waste is placed at the current WGSL each year?

Approximately 225,000 tons per year, including municipal solid waste, H-POWER ash, non-combustible materials and special waste.

  1. Will there ever be a time when Oʻahu does not need a landfill?

Even with advances in waste reduction, recycling and conversion technologies, landfills remain critical infrastructure. Landfills are required for:

  • Disaster debris management (e.g., Kona Low storm debris or Lahaina fire debris, or hurricane debris)
  • Non-combustible and special wastes
  • Waste-to-Energy (WTE) facility ash (H-POWER)
  • Residuals from any future innovative/alternative waste processing technology (slag, glass, biochar, etc.)
  • Backup disposal of MSW when facilities such as H-POWER, future innovative/alternative technology process, are offline for maintenance.

Additionally, Department of Health solid waste permits for operation of H-POWER and other ENV waste management facilities specify that a landfill is required for disposal of residuals.

  1. Why can’t we just use H-POWER to burn all the trash?

H-POWER generates ash and non-combustible residue that must be disposed of at a landfill. Also, some materials cannot be processed at H-POWER including:

  • Non-combustible waste
  • Medical waste sharps
  • Animal carcasses
  • Auto shredder residue

When H-POWER is out of service due to maintenance or operational issues, waste must be diverted to a landfill to maintain uninterrupted refuse collection.

Federal EPA regulations also require the City to have a landfill as part of its waste-to-energy operations.

  1. Can the H-POWER ash be recycled?

    The City has investigated ash recycling for at least 20 years and continues to do so. There are multiple challenges to recycling ash, including different processing technologies, public and regulatory concerns about reuse scenarios, and permitting requirements. The City is currently starting to pilot test of an enhanced metal recovery from ash system. The recovered metals can be recycled via existing markets and could potentially reduce the volume of ash by 30-40%. The City continues to investigate the processing of about 50-60% of the ash into sand/aggregate substitute for use in asphalt paving and/or structural concrete. There has been significant concern expressed by the public, the legislature, and the DOH regarding this recycling scenario.  

  2. How do we know this landfill won’t contaminate our drinking water or pose any other health risks for the residents who live nearby?

Landfills are subject to strict environmental and public health regulations and must include multiple protective measures, such as:

  • Engineered bottom liners
  • Leachate collection and treatment systems
  • Stormwater management systems
  • Landfill gas collection and flaring
  • Daily top cover for active areas
  • Final cover system upon closure
  • Upgradient and downgradient groundwater monitoring wells

These measures are designed to protect groundwater, surface water, air quality and nearby communities.

In addition, the existing Waimānalo Gulch Sanitary Landfill has been in operation since 1989 and has not experienced a liner system breach. Modern landfill design and regulatory oversight continue to build on these proven protections.

  1. Several Windward locations were previously identified. Why aren’t those sites being used?

Previously identified sites are restricted by state laws (Act 73 and Act 255) enacted prior to and during the current landfill siting process. A map and detailed explanation of these legal restrictions are available on the City’s website: https://www.honolulu.gov/env/ref/new-landfill-siting/

  1. What is the City going to do for the community surrounding the landfill?

ENV plans to provide a host community benefit package funded by landfill tip fees and possibly other funds. A community advisory group made up of local residents will be formed to help guide how those funds and benefits are allocated to support and enhance quality of life in the surrounding area.

  1. What will the landfill look like? What is being done to prevent it from being an eyesore on the top of a mountain for all to see? What about the odor during the downwinds?

Visual simulations showing the predicted appearance of the landfill are available at:  https://www.honolulu.gov/env/ref/new-landfill-siting/.

The landfill will operate one cell at a time, with a limited working face. Areas not actively being filled will be covered and landscaped, appearing similar to a grassy hill.

Odor control measures, including daily cover and gas management systems, are required as part of landfill operations.

  1. Will there be further public or community hearings on the proposed landfill extension site? What type of permits/approvals are still needed in which there is an opportunity for public input? Is the land already zoned for this kind of use?

Yes. The landfill expansion will be subject to public review and input opportunities. The landfill will require an Environmental Impact Study (EIS), a special use permit (SUP) from the State Land Use Commission (LUC) both of which require public hearings. The landfill will also require a solid waste permit from DOH, and an air permit from DOH and other permits from the City. The land is currently zoned for Agriculture.

  1. How will this impact property values for homeowners in the surrounding community?

The landfill expansion will be located adjacent to the existing landfill which has been there since 1989. It will be visible from areas below Farrington Hwy similar to the existing landfill. Thus, no impacts on nearby property values are anticipated.

  1. What alternatives were considered before deciding on this expansion?

The City evaluated multiple alternatives, including waste export, expanded recycling and diversion, and numerous other landfill site options. Each alternative presented significant cost, legal or logistical barriers. All other potential sites were either barred due to legal restrictions, or unavailable (Federal lands). Expanding the existing landfill was determined to be the most feasible and implementable option at this time, providing approximately 20 years of additional disposal capacity while longer-term strategies continue to be pursued.

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