The City and County of Honolulu (“City”) Department of Environmental Services (“ENV”) has begun identifying potential sites for its next municipal solid waste landfill. To help discern potential sites, ENV formed a Landfill Advisory Committee (“LAC”) to evaluate the sites identified to meet current State regulations. The LAC process is documented in the Final Report. See below for details. 

After consideration of the LAC’s evaluation of six identified potential sites, all of which are located above Oʻahu’s drinking water aquifer system, and conclusions and information provided by the Honolulu Board of Water Supply, the City has formally submitted an application to the Planning Commission to request modification of the conditions that set a December 31, 2022 deadline for the City to identify an alternative landfill site. These conditions are found in both the Planning Commission’s Findings of Fact, Conclusions of Law, and Decision and Order, dated June 10, 2019, and the Hawaiʻi Land Use Commission’s 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 on November 1, 2019. These are the related documents: Special Use Permit ApplicationDeclarationExhibits.

Because of their direct involvement in the siting process, the LAC Members were sent an official letter to inform them of these developments.

This webpage, along with ENV’s Facebook and Twitter 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

Questions and Answers

Click on the questions below to view the answers. Any additional questions or comments about the landfill siting process may be sent to

General Questions

Q1: How much waste goes into the landfill?

A1: Currently, approximately 250,000 tons of waste go into the landfill per year, with roughly 72% being ash and residue from H-POWER. The amount of waste going to the landfill has been significantly 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.

Q2: What are some frequently used solid waste/landfill terms and acronyms?

A2: These 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.
  • Waimanalo 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 webpage.
  • 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. Around 1,000,000 tons of C&D waste is generated every year on O’ahu.
  • 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.

Q3: Why do we need a landfill when we recycle and have H-POWER?

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.

Q4: Can dead animals not go to H-POWER at all?

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.

Q5: Why do you only accept construction and demolition (C&D) waste from homeowners?

A5: Our convenience centers are only for homeowner use and our transfer stations are primarily for homeowner use and they have limited capacities, so we have limitations in place to maintain service as much as possible. Similarly, at WGSL, C&D is only accepted from homeowners to maximize the landfill life.

Q6: Is the City looking at other countries and the way they deal with their trash, e.g., Japan builds landfills that expand their land area?

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.

Q7: What is the composition of the ash that comes out of H-POWER? Does the composition vary greatly or does it stay relatively the same?

A7: The composition of the ash is relatively consistent. For a detailed composition of the ash, view the ash characterization reports which includes the final analysis of ash samples collected in the 2nd quarter of 2021.

Q8: If a complex contaminant from leachate does make it into the drinking water, who pays the additional cost for treating the water?

A8: If treatment is required to provide for fresh, clean drinking water then, generally, the party responsible for the contamination pays for the treatment. In the case of a current or future City and County of Honolulu 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: ENV is working with a consultant to identify potential sites on O’ahu. The LAC will rank the potential sites while considering public input. The LAC’s recommendation will be presented to the Mayor, who will ultimately make the final decision.

Q2: When will the public be able to engage in the new landfill process?

A2: ENV values the opinions of O’ahu’s residents – take our Resident Landfill Survey to contribute. The survey results will be presented to the LAC. At each public committee meeting, there will be a public comment period. After the site selection process, there will be more opportunities for public comment, which ENV will announce.

Q3: When will the Landfill Advisory Committee be meeting?

A3: The exact meeting dates for the Landfill Advisory Committee meetings have yet to be determined; however, the meetings are currently planned to take place between October 2021 and June 2022. ENV will notify the public via press releases, social media, and this webpage.

Q4: Why was the No Pass Line, above which installation of waste disposal facilities is prohibited by the Board of Water Supply, not used to exclude sites in preparing for the landfill selection?

A4: Act 73 severely limits potential landfill areas and so areas that have been dismissed previously are now necessary to consider. Remaining areas after applying Act 73 are above the No Pass Line.

Q5: How does WGSL score with the criteria being considered for this evaluation?

A5: WGSL is not being considered and will not be evaluated in this current effort.

Q6: Why is the City going through the landfill siting process?

A6: 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.

Q7: What are the exact locations for the new proposed landfill?

A7: The City has not yet determined the exact parcels to be considered for the potential placement of a new landfill. It is currently in the process of looking at each individual parcel in the four defined areas to determine eligibility.

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 Hawaii 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.

Q2: What’s going to happen to Waimanalo Gulch Sanitary Landfill when it closes?

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

Q3: What environmental safeguards are in place at Waimanalo Gulch Sanitary Landfill to protect the environment?

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.

Q4: What is the composition of the leachate from WGSL and what happens to it?

A4: Landfill leachate is collected and taken to Honouliuli Wastewater Treatment Plant for treatment and disposal. View the City’s Leachate Management Plan and the Leachate Management report detailing the composition of the leachate at WGSL.

Q5: What is the groundwater monitoring program like for WGSL?

A5: View the First Semi-Annual 2021 Groundwater and Leachate Monitoring Report detailing the groundwater monitoring program and the summary of sampling results.

Q6: How much leachate is generated at WGSL and what affects how much is generated?

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.

Q7: How many leachate monitoring wells are currently at WGSL?

A7: The monitoring wells at WGSL and would be at a landfill are actually groundwater monitoring wells. They are present to be sampled in order to check to see if any contamination is around the landfill. Leachate from the landfill is one possible source should contamination be discovered. There are currently nine groundwater monitoring wells that are sampled from regularly around WGSL.

Sign In


Reset Password

Please enter your username or email address, you will receive a link to create a new password via email.


An active membership is required for this action, please click on the button below to view the available plans.