Department of Environmental Services

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Refuse Division

New Landfill Siting

City selects area northwest of Wahiawā as
proposed site for new landfill on O‘ahu

Map showing the approximate location, northwest of Wahiawā, of the Cityʻs proposed landfill location.
Map showing the approximate location, northwest of Wahiawā, of the cityʻs proposed landfill location.

Oʻahu Landfill Siting Study & Landfill Advisory Committee Recommendations, Final Report

O‘ahu Landfill Siting Study Supplemental Technical Memorandum

Mayor’s Message – The City and County of Honolulu to Identify New Landfill Site on Oahu before December 31, 2024

The City and County of Honolulu has identified a location northwest of Wahiawā as the proposed site for Oʻahu’s next landfill, following an extensive and transparent evaluation of all legally permissible options. This decision, announced ahead of the Dec. 31, 2024, deadline set by the state Land Use Commission, marks a critical milestone in the city’s efforts to responsibly close the Waimānalo Gulch Sanitary Landfill (WGSL). The selected location, identified as “Area 3, Site 2” in the Landfill Advisory Committee’s 2022 report, sits on agricultural land and was chosen based on a balance of regulatory compliance, environmental considerations, and community equity.

The city is committed to exceeding state and federal design standards to ensure the safety of the proposed facility, particularly in protecting Oʻahu’s vital aquifer system. The new landfill will incorporate advanced engineering and multiple barriers to prevent environmental contamination and will undergo a comprehensive Environmental Impact Statement (EIS) process. This process will include extensive public engagement and consultation with stakeholders, including neighborhood boards and area legislators. The Department of Environmental Services (ENV) will continue to update this webpage with the latest developments, including documentation, and maps, as the project moves forward.

 In 2021-2022, ENV formed a Landfill Advisory Committee (“LAC”) to evaluate potential landfill sites identified to meet current federal and state regulations. The LAC process, which concluded in June 2022, is documented in the Oʻahu Landfill Siting Study & Landfill Advisory Committee Recommendations, Final Report.  See the Advisory Committee tab below for additional details.

Following the conclusion of the LAC process, the city formally submitted an application (“Modification Application”) to the Planning Commission to request modification of the conditions that set a Dec. 31, 2022, deadline for the city to identify an alternative landfill site. The conditions can be found in:

  1. The Planning Commission’s Findings of Fact, Conclusions of Law, and Decision and Order, dated June 10, 2019, and
  2. The Hawaiʻi Land Use Commission’s (LUC) Findings of Fact, Conclusions of Law, and Decision and Order Approving with Modifications the City and County of Honolulu Planning Commission’s Recommendation to Approve Special Use Permit, certified Nov. 1, 2019.

Related documents: Special Use Permit Application; Declaration; Exhibits.

On Aug. 23, 2024, the Modification Application was granted by the LUC extending the deadline to identify an alternative landfill site by Dec. 31, 2024. In conjunction with the decision, ENV must report quarterly to the Planning Commission on the siting efforts leading up to the modified deadline. The reports are described by the following:

  • Reports should include but are not limited to timelines, milestones, schedules of tasks for the specific plan to have a site selected by Dec. 31, 2024.
  • List of potential sites under consideration
  • List of obstacles [sic] their ability to choose a site
  • Reporting on the investigation of alternative technologies for landfill (2019 LUC Decision)

ENV reported to the Planning Commission Sept. 18, 2024, for the third quarterly update (slides) and Nov. 20, 2024, for the fourth quarterly update – transcript and slides. (Planning Commission webpage).

This webpage, along with ENV’s social media accounts, will be updated with new information as the landfill siting process progresses. Like and follow us to get the latest updates! If you would like to be notified of future updates to the landfill siting process by email, please send an email to newlandfill@honolulu.gov.

Waimanalo Gulch Sanitary Landfill

More Information

The restrictions considered by ENV when identifying potential sites for the next landfill involve restrictions mandated in Act 73 and other restrictions regulated by the state. Click on the map to view the restricted areas for O‘ahu.

When all restriction layers are activated, the uncolored regions show all areas within which the next landfill could be sited. Click on the image above to view the interactive map.
 

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

Questions and Answers

Click on the question categories below to view the questions and answers. Any additional questions or comments about the landfill siting process may be sent to newlandfill@honolulu.gov.

General Questions

Q1: How much waste goes into the landfill?

A1:  An average of 250,000 tons of waste go into the landfill per year, with roughly 65% being ash and residue from H-POWER. The amount of waste going to the landfill has been reduced over recent years as a result of the city’s ongoing landfill diversion efforts. Waste has been diverted from the landfill through business recycling requirements, curbside recycling via the blue and green carts, recycling drop-off sites, and more. Waste that isn’t recycled goes to H-POWER, where it is burned to generate electricity and the volume is reduced by 90% to ash.

A2:  Below are some frequently used solid waste terms and acronyms:

  • Municipal Solid Waste (“MSW”): The everyday residential and commercial trash that ends up at a waste disposal site after collection.
  • Waimānalo Gulch Sanitary Landfill (“WGSL”): The city’s currently active MSW landfill.
  • Honolulu Program of Waste Energy Recovery (“H-POWER”): The city’s waste-to-energy facility. Learn more by going to the H-POWER
  • Ash: The remaining byproduct from burning waste to generate electricity at H-POWER that must currently be landfilled.
  • Residue: Small particles of dirt, sand, grit, and other refuse generated while processing waste at H-POWER. Residue cannot be burned and must currently be landfilled.
  • Construction and Demolition (“C&D”) Waste: Waste generated from the destruction of old facilities and the construction of new facilities.
  • 2012 Mayor’s Advisory Committee from Landfill Site Selection (MACLSS): The committee formed in 2012 to rank and recommend landfill sites for the city. The result of the MACLSS was a final report submitted to the mayor.
  • Landfill Cell: A discrete subdivision of a landfill which uses a liner to provide isolation from wastes or adjacent cells.
  • Working Face: The active area of the landfill where waste is being accepted, spread, and compacted.

A3:  Ash and residue are byproducts of the H-POWER waste-to-energy process. The city is pursuing ash recycling, but those materials must be landfilled until there is an alternate use. Other materials, such as non-combustible waste, medical waste sharps, and dead animals, cannot be recycled or managed at H-POWER and must be landfilled. Furthermore, if H-POWER is unavailable (due to maintenance, etc.), diversions to the landfill may be necessary to continue refuse collection.

A4: H-POWER will take small amounts of small dead animals or animals that happen to be in the waste, but large or large amounts of dead animals are not accepted at H-POWER.

A5:  City convenience centers and transfer stations are for homeowner use (with some transfer stations accepting business accounts) and have limited capacities. Thus, restrictions are put in place to maintain continued service as much as possible. Similarly, at WGSL, C&D waste is only accepted from homeowners to maximize the landfill’s life.

A6: The city has been keeping up with how other countries are dealing with their trash and has looked into other technologies, such as plasma arc, to reduce the amount of trash that needs to be landfilled. However, this does not absolve the city of its obligation to identify a future landfill site.

A7:  The composition of the ash is relatively consistent. Ash continuously tests as non-hazardous with results notably within the regulatory limits.

A8:  If treatment is required to provide for clean drinking water, typically, the party responsible for the contamination pays for the treatment. In the case of the current or future city landfill, depending on the exact cause of the contamination, the operator and/or the city itself would be responsible and pay for the treatment.

New Landfill Questions

Q1: Who will decide where the next landfill will be?

A1:  The Mayor of the City and County of Honolulu will ultimately make the final decision on the location of the next landfill. Data from technical consultants and input from the public is important in the decision-making process.

A2:  The new landfill siting is ongoing, and there are several opportunities for public engagement. The public may testify during neighborhood board meetings, Honolulu City Council hearings, Hawaiʻi state legislative hearings, and other public meetings. In addition, during the Environmental Impact Statement process, there will be periods for public comment.

A3:  Act 73 severely limited the options for a new landfill site. Therefore, areas that were previously dismissed remain under consideration. The remaining potential landfill sites, after applying Act 73 restrictions, are within the No Pass Line.  Currently, there is state legislation that further restricts landfill siting options. Follow SB438 and HB969 for the latest status on legislation.

A4:  WGSL was not considered and not evaluated in the original effort.

A5:  Due to the conditions of WGSL’s Special Use Permit, the city needs to “identify an alternative landfill site that may be used upon closure of WGSL,” and WGSL must stop accepting waste by March 2, 2028.

A6: The city selected a location northwest of Wahiawā as the proposed site for Oʻahu’s next landfill ahead of the Dec. 31, 2024, deadline to identify an alternative landfill site. However, there is recent state legislation that may affect the selection of this site. Follow SB438 and HB969 for the latest status on legislation.

Waimanalo Gulch Sanitary Landfill Questions

Q1: Where is the city's current landfill?

A1: WGSL, in Kapolei, is the only active landfill owned by the city. Waste Management of Hawai‘i operates the landfill under contract with the city. It has been located there since 1987, but must be closed by March 2, 2028, per decision and order of the state of Hawai’i Land Use Commission. Visit the WGSL webpage for more information.

A2: The city must conduct post-closure care and monitoring of groundwater, stormwater, leachate, and landfill gas for at least 30 years.

A3: Landfills are one of the most heavily regulated industries in the country. Federal landfill regulations fall under Subtitle D of the Resource Conservation Recovery Act (RCRA) and the Clean Air Act. Stormwater is regulated under the National Pollutant Discharge Elimination System (NPDES). The state of Hawai’i also has its own solid waste rules and reporting requirements under Hawai’i Administrative Rules Chapter 11-58.1. Incoming material loads, leachate, groundwater, surface water, stormwater, gas, stability, liner construction, cover soil/tarps, and any potential dust, odor, vectors, and litter are continually managed and monitored at WGSL.

A4: Landfill leachate is liquid that percolates through the landfill cells and is collected by sumps installed above the liner and pumped to holding tanks on the surface.  Leachate is collected by tanker trucks and hauled to Honouliuli Wastewater Treatment Plant for treatment and disposal.

A5: Groundwater around the landfill is monitored for any leaks or contaminants by a network of monitoring wells.

A6: The amount of leachate collected each month ranges from 150,000 gallons to nearly 1,000,000 gallons. The range predominantly depends on rainfall, but other factors include depth of the landfill cells, types of waste being buried, moisture content of waste, size of the working face, topography and watershed effects, etc.

A7: The monitoring wells at landfills such as WGSL are actually groundwater monitoring wells. There are currently nine (9) groundwater monitoring wells around WGSL that are sampled semi-annually to confirm the presence of any contamination from or around the landfill. Leachate from the landfill is one possible source should contamination be discovered. Common sources unrelated to the landfill include, for example, fertilizers applied by neighboring activities such as parks, golf courses and landscaping maintenance. 

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