Protecting the Ocean & Environment
Updated over a week ago

Why isn’t the ash and debris being taken off the island for disposal?

For logistical, safety and environmental reasons, it would be extremely difficult. The process of staging, packaging, loading and unloading to/from ships, and loading onto trains or trucks for transport to facilities on the mainland is not feasible given existing infrastructure, both on Maui and the mainland. For example:

  • ash/debris from the West Maui TDS site would need to be excavated, loaded onto trucks (currently estimated at 40,000+ trips), and transferred to Kahului Harbor, which is a heavily populated area;

  • a temporary debris storage (TDS) area would have to be constructed immediately adjacent to Kahului Harbor, which lacks sufficient space and would pose a risk to the marine environment;

  • a large crane would need to be erected at the harbor between the TDS and the ship to load out the ash/debris;

  • the ship would require an adequate port on the west coast of the mainland with adequate handling equipment (large crane) to off-load the ash/debris from the ship onto railcars for shipment;

  • the ash/debris would have to be shipped by train to licensed landfill facilities which can accept rail haul waste.

This approach would extend the timeframe for cleanup by months to years. In addition, it would increase the overall environmental impact of the cleanup and risk of an accident or spill in transport, staging at the ports, and loading and unloading immediately adjacent to the ocean.

Can the ash and debris be temporarily placed in shipping containers in Lahaina while the permanent disposal site is being constructed?

No. This option is not feasible as the volume of ash and other fire debris equates to thousands of shipping containers which would require acres of open space for temporarily storage. Moving and loading containers requires large cranes and heavy equipment which further complicates logistics.

Why can’t USACE just wrap all the debris in plastic and leave it until the permanent disposal site is built?

Plastic wrapping is only used to encapsulate debris to suppress dust while the debris is being transported from parcels to the TDS and is not sufficient to contain debris for an extended time without additional mitigation. The neighborhoods in Lahaina are too dense to store the debris in town and have room to complete the needed clean-up work. Leaving the debris, whether wrapped or not, in the burn zone prevents recovery work like utility restoration, historic structural preservation efforts and rebuilding from moving forward.

Is ash and debris from commercial properties being handled differently than from residential properties?

Yes. The ‘household waste exclusion’ in federal solid waste law only applies to ash and debris from single and multiple residences, hotels, and other residential structures. It allows for waste from these properties to be disposed of in a municipal solid waste landfill without sampling and testing to determine if it may be a hazardous waste. This exclusion does not apply to commercial structures such as shops, restaurants, and other businesses. Ash and debris from these structures must be sampled and analyzed by a laboratory to determine if it is hazardous and therefore subject to stricter handling, management and disposal requirements. US ACE will follow a sampling and analysis plan for ash and debris from commercial properties, and the material will be separated and/or treated to stabilize it or managed according to applicable hazardous waste regulations if necessary.

How will the ash and debris be removed and transported safely to the temporary debris storage (TDS) site and permanent disposal site?

Ash is collected by hand tools (rakes and shovels), mini-excavators and front-loaders into dump trucks where the ash and debris is encapsulated in an impermeable plastic layer, prior to leaving the property to prevent any spillage or dust generation during transport. The trucks follow designated routes to the temporary debris storage (TDS) and/or permanent disposal site. Sensitive dust monitors are placed at both the source and destination locations. Loads are slowly dumped out to avoid generating dust, as the plastic layer commonly breaks open as the load is dumped out and heavy equipment spreads it into ‘lifts’ in the TDS or permanent disposal site to create a stable, engineered fill. Dust is controlled by water misters applying a gentle spray of water and the ash/debris is covered as soon as possible to prevent any debris from blowing away. The TDS area is lined with a heavy (80 mil or 0.08” thick) HDPE plastic liner to prevent leaks and are covered daily to avoid drying and dust generation. USACE oversees all contractors involved in this process.

Why did the County prioritize locating the temporary debris storage (TDS) area in the moku of Lahaina?

Being close to Lahaina, the time spent to haul, exhaust emissions and potential of having to shut down hauling operations due to an accident on the Pali is greatly reduced. Avoiding having to traverse the Pali with tens of thousands of large construction trucks improves the safety of both the hauling crews and the general public. The location of the TDS has an added benefit of providing clean fill (native gravel) displaced to build the TDS site, which is hauled back to the properties for backfilling on scraped parcels.

Do the levels of contamination in the ash make the debris a ‘hazardous waste’ regulated under Resource Conservation and Recovery Act (RCRA) or Superfund (CERCLA)?

No. From a regulatory perspective, ash and debris area considered ‘household waste,’ which is different from ‘hazardous waste’ designation, and can be managed at municipal solid waste landfills, such as the Central Maui Landfill, according to federal solid waste law (Resource Conservation and Recovery Act, or ‘RCRA’). Though the levels of arsenic, lead and cobalt make the ash harmful to human health (via exposure to skin or inhalation), these levels of contamination do not necessarily make the waste a ‘hazardous waste.’ A thin (1/2 – 1” thick) layer of ash will be removed along with underlying soils (up to a 6” thick layer). When this material is mixed together, it is unlikely to contain leachable levels of contaminants that would classify the material as a ‘hazardous waste’ per federal regulations.

The County of Maui is not proposing to construct a RCRA hazardous waste (Subtitle C) permanent disposal site. The County is fulfilling Mayor Bissen’s request to provide the safest solid waste management facility possible.

Does the ash or debris contain dioxins and/or furans at dangerous levels?

Though detectable levels of dioxins and furans were found in ash samples collected by Hawai’i DOH (see, they are not considered harmful to human health according to Hawai’i DOH guidance on dioxins and furans in soils found at:

Dioxins do not typically exist in materials before they are incinerated. However, when materials and waste are burned, dioxins are produced and introduced into the environment. A large part of current exposures to dioxins in the U.S. is due to releases that occurred decades ago (e.g., pollution, fires). Even if all human-generated dioxins were eliminated, low levels of naturally produced dioxins would remain. More than 90% of typical human exposure is estimated by USEPA to be through the intake of animal fats, mainly meat, dairy products, fish, and shellfish.

Is the ash toxic (DOH results from testing showed arsenic, lead, antimony, copper, and cobalt)?

The Hawai’i Department of Health (DOH), Hazardous Evaluation and Emergency Response (HEER) Office, collected samples for laboratory analysis of just the ash from parcels in Kula, Olinda and Lahaina. DOH’s ash characterization testing screened for heavy metals, polyaromatic hydrocarbons (PAHs), residual range organics, dioxins and furans, per- and polyfluorinated substances, flame retardants such as polybrominated diphenyl esters and organophosphates esters, asbestos, and organochlorine pesticides.

These results found elevated levels of arsenic, lead, antimony, copper and cobalt at levels determined by health agencies to be potentially harmful to humans in direct contact with it. This is why it needs to be collected and removed from the ground as soon as possible to reduce the risk of rainwater run-off or wind erosion. Ash sampling results, along with safety recommendations can be found at:

Where did these contaminants come from?

Antimony is naturally present in soils. The general population is exposed to low levels of antimony from ingestion of food and drinking water and possibly by inhalation of particulate matter containing antimony in ambient air.

Arsenic is a heavy metal found in soils in Hawaii due to volcanic soils and its use as an herbicide in the early 1900s. It is also found in building materials made of sugar cane (Canec) and wood treated for termite control (CCA treated wood). Arsenic can also be found in food such as rice, meats, fish and seaweed and has also been found to be naturally occurring in well water around the world. Long-term, environmental exposure to arsenic can cause skin problems, heart problems and cancers of the skin, bladder and lungs.

Cobalt is a naturally occurring element that is essential for certain functions of the body including the generation of red blood cells. People are exposed to small amounts of cobalt in food, industrial air pollution, and many cosmetics. However, when people are exposed to excessive amounts of cobalt, it can cause problems with the blood, lungs and skin. Cobalt may also cause cancer with extreme exposures.

Copper is a chemical element and essential trace mineral that is a reddish metal which occurs naturally in rock, soil, sediment, water, and at low levels, air.

Lead is a heavy metal that is expected to be present in ash due its use in paint on houses built before 1978. Lead is particularly toxic for young children and babies in utero as it hinders the development of the brain. Babies and children exposed to lead have trouble with learning, school performance, attention, and other neurocognitive problems.

Considering data showing elevated levels of heavy metals in the ash, are any heightened protective containment measures or methods being designed for transport as well as at the TDS? Has Maui County engaged toxicity experts to help understand heightened risks of transport and disposal?

Yes. Maui County is working closely with experts from Hawai’i DOH, USACE and USEPA to manage hazards to the greatest extent possible. Maui County, USACE and FEMA are committed to ensure the minimum possible exposure to public and environment.

USEPA and Hawai’i DOH will review any design plan(s) for the permanent disposal site when they are developed with respect to the proposed liner system to ensure that it is sufficient to contain Lahaina wildfire debris, the adequacy of Seismic Stability Analysis, and the Groundwater Monitoring Plan/Groundwater Protection Plan.

People can take action to minimize their exposure to these contaminants including avoiding disruption of ash and wearing proper PPE (personal protective equipment) when in impacted areas. In addition, for people near the impacted areas, keeping surfaces clean of dust and ash and frequent hand washing will greatly reduce potential exposure.

How will recyclable materials be safely handled?

Any concrete, brick, and metals is rinsed off and collected for recycling at established facilities on Maui.

What about asbestos? How will it be managed?

Bulk asbestos containing materials (ACM) that could be removed by USEPA during Phase 1 operations has already been shipped off-island. Similarly, USACE has also begun removing and shipping additional bulk ACM from parcels and will continue to do so throughout the Phase 2 mission. Remaining ACM associated with building materials such as siding, caulk, floor tiles, and insulation will be managed along with the ash and debris carefully to avoid disturbing it and by application of a gentle water spray for dust control during collection, transport and handling in both the TDS and permanent disposal site.

Is there a risk of rainwater run-off from the ash into the ocean or other surface waters?

The best course of action to reduce ash runoff is to expedite the removal of ash from affected properties in Lahaina. Erosion control features called best management practices (BMPs) have been placed around storm drains to reduce run-off from neighborhoods. USEPA soil stabilization efforts in Lahaina primarily serve to control dust, but these efforts also help mitigate runoff. Once ash and debris reach the TDS and permanent disposal site, this risk is significantly reduced by runoff control features, leachate collection and an impermeable liner.

Is there a risk that contaminated leachate (i.e., liquids from the waste) could escape the site and contaminate the ocean?

No. First, the site was designed with a canal system around the TDS to divert surface-water running into the area from the surrounding hills around the waste footprint, preventing it from entering the ash and debris storage area. Second, any precipitation falling into the TDS footprint is collected and drained into a leachate basin lined with the same 80 mil HDPE flexible membrane liner as the ash and debris storage area, which keeps it from infiltrating into the ground. This leachate basin has a design capacity of 1,375,000 gallons, which far exceeds normal design standards to afford a greater protection. Its effectiveness was demonstrated during a recent rainfall event in January in which 3” of rain fell within 24 hours. The event filled the leachate basin with approximately 500,000 gallons, just over 1/3 of its capacity. Leachate collected in the leachate basin is being pumped out and utilized for dust control on the ash and debris storage area to prevent dust blowing off the ash and debris as well as the cover placed on top. This allows for the majority of the applied leachate to evaporate.

Is there a risk that contaminated leachate could escape the TDS and contaminate groundwater?

The TDS is located approximately 1.25 miles downgradient from the Olowalu water system source well. The distance from the source wells of a public water system (PWS), geology of the area, and the PWS wells located upgradient of the water systems makes it highly unlikely that any potential release from the debris TDS would reach the water system. Planned groundwater quality monitoring by USACE will detect any release well before it would reach any drinking water sources. Alternative water use in this situation is not necessary.

Will the air be monitored around the cleanup area and TDS? How will the public know if the air quality is bad?

Yes. Sensitive dust monitors specifically designed for this purpose will be set up each day by trained personnel during all excavation and dumping operations. The public will be able to view air monitoring data at or

As this area is known for very high winds that may exacerbate air and marine pollution concerns, are there mitigation methods for airborne contaminants being developed to protect the environment and community areas from the ash and debris being disturbed, cleared, and then deposited?

Ash and debris in parts of the impacted areas have been temporarily stabilized through application of a product called SoilTac, which binds with the ash/debris to prevent it from being blown or washed away. There are several operational environmental controls that will be used to prevent ash and debris from escaping, including the use of water misters to minimize dust, wrapping debris in plastic and covering loads during transport, and covering the debris at the TDS area at the end of the day. Operations are suspended during high winds. Finally, air quality monitoring is also conducted throughout cleanup and disposal, and operations are adjusted should air monitoring detect any issues.

What is the minimum efficacy of the HDPE liner at the temporary debris storage (TDS) site to prevent leaching of toxins and contaminants that can pollute groundwater or harm marine life?

The protective system is comprised of an 80 mil (0.08” thick) high-density polyethylene (HDPE) liner, which come in rolls and are welded together in the field. All HDPE welds are quality controlled and certified on location in the field during construction. The minimum efficacy could be interpreted as the 3’ of low permeability soil. When properly maintained, the HDPE liners may need to be repaired, but will not need to be replaced.

This type of liner is well-suited to resist any contaminants found in the ash and debris, including heavy metals (i.e., lead, antimony, arsenic, cobalt, copper) as well as dioxins. Further these contaminants have been shown to have limited mobility within this type of waste mass, especially in the dry and remote conditions in West Maui.

Will an Environmental Assessment (EA) and/or Environmental Impact Study (EIS) be performed for the permanent disposal site?

Investigation pursuant to the National Environmental Protection Act (NEPA) is required. Though Maui County and USACE/FEMA will consider the human and natural environment in the NEPA document for the permanent disposal site at the Central Maui Landfill, most of this work has already been completed as the Central Maui Landfill is currently operating as a solid waste landfill.

What type of liner was used?

A thick, heavy-duty, High Density Polyethylene plastic (80 mil, or 0.08” thick HDPE) liner was used in construction of the TDS site. The liner comes in large rolls and is heat-welded together with strict quality control procedures. The plastic is resistant to the contaminants which are found in the ash and debris. The liner system for the permanent disposal site has not been designed yet.

How will the permanent disposal site be built to be protective of human health, wildlife, agricultural lands, marine life, and the environment?

Disposal cells within the Central Maui Landfill are already built to stringent design standards intended to encapsulate the ash and debris between heavy plastic and clay composite liners (base and final cover) specifically designed for this purpose. Debris will be contained within the site and prevented from blowing onto adjacent lands or the ocean. In addition, regular supervision and maintenance to remove leachate to mitigate any potential leaking of contaminants, will be performed. Finally, groundwater monitoring wells are installed around the Central Maui Landfill to detect any changes to groundwater conditions.

Can opportunities be developed to include bioremediation of the toxic ash prior to Phase 2 removal as well as at the deposition site? (Bioremediation involves using biological agents such as plants, fungus, and microbes to remove or lessen the effects of environmental pollutants.)

Bioremediation requires controlled conditions (set moisture, temperature and oxygen levels along with an adequate organic substrate to support growth and survival within a waste mass), and long periods of time (many months to years) to complete remediation. These conditions are not currently present in Lahaina, where ash and debris containing non-organic and non-degradable debris (such as concrete, asphalt, metal, glass, ceramics, rubber and drywall) are spread out in an uncontrolled manner among burned structures with concrete foundations, paved surfaces, standing walls, and partial structures still in place.

Biofiltration (aka ‘mycofiltration,’ which utilizes fungi to biodegrade toxins) was utilized on an experimental basis after the California wildfires to control ash/debris from running off impacted properties prior to cleanup in rainwater and prevent it from impacting adjacent rivers, streams and/or lakes. It is important to note that bioremediation does not reduce the amount of ash/debris which still ultimately needs to be removed and managed. Even if conditions supported bioremediation in Lahaina and were fully successful in achieving reductions in heavy metal concentrations in the ash, it would all still need to be completely removed and staged at the TDS site and ultimately disposed of in a permanent disposal site. Further, it is not necessary to reduce the levels of contamination in the ash as the TDS site and proposed permanent disposal site are being designed and constructed in a manner to contain any contamination and prevent it from impacting groundwater or adjacent surface waters. Finally, the application of bioremediation prior to Phase 2 removal would significantly increase the timeline for the Lahaina recovery and the risk to the population and environment, due to the uncontrolled state of the ash/debris throughout Lahaina.

Can alternative technologies besides disposal be used to treat, recycle or beneficially use the ash/debris?

Concrete and metals, which represents approximately 25% of the ash/debris being removed, are being separated, rinsed and sent for recovery and recycling on the island. Though alternative technologies such as pyrolysis, anaerobic digestion, or gasification continue to be developed by academia and industry, they are not considered practical for the wildfire ash/debris in Lahaina from a legal, technical or logistical perspective. Aside from the developmental nature of these technologies (very few if any commercially viable facilities exist), the amount of space needed, siting requirements, time and cost to permit and construct, energy required, and composition of the ash/debris (which contains pieces of glass, ceramic tile, rubber, granite, masonry, drywall and metal) make these options unable to respond to the scale of the wildfire debris on Maui in a timely and responsible way. Also, even if these technologies were viable on Maui, they would still need to properly manage a substantial volume of solid byproduct generated by the process, which currently have limited commercial or agricultural applications, as these products are derived from waste material.

To learn more about these emerging technologies, see these reports from USEPA:

- “State of Practice for Emerging Waste Conversion Technologies’ (

- “Assessment of Municipal Solid Waste Energy Recovery Technologies” (

Can the ash/debris be encapsulated in a "pool" of cement like a mausoleum?

The permanent disposal site will in effect be the same as encapsulation, without the substantial amount of cement that would be required. If ash/debris were to be encapsulated in cement, there would also be increased chances of leaching, leakage during staging, production, mixing and solidification as it would be exposed during the process.

How long will the HDPE liner at the TDS last? Will the liners rip or tear as waste is being placed into the TDS?

After installation, the HDPE liner is covered with a geotextile (a thick fabric) and 2’ thick layer of sand, soil or gravel on top prior to waste placement to prevent any waste items from piercing or ripping the liner during placement. When properly maintained and protected, the plastic liner will last a very long time, as they are resistant to subsurface conditions, waste-derived liquids (leachate), and are considered state of the art in decades of landfill construction worldwide. Regardless, the site will continue to be monitored by Maui County along with the other closed landfills on the island.

What is being done to minimize the potentially harmful effects of toxins in the ash / debris on human and environmental health?

The wildfire ash, dust and debris must be removed as quickly as possible and according to accepted safety standards. The first phase of this effort, overseen by USEPA, was completed in December 2023. The second phase, which is being undertaken by USACE, includes encapsulating the ash and debris from Lahaina in an impermeable plastic layer, securing and covering it, and trucking it to a temporary debris storage area. Debris and ash from the Kula/Olinda/Makawao impacted areas were transported and disposed of at the Central Maui Landfill. Contingency plans are in place to respond to any accidents or spillage during transport.

People can take action to minimize their exposure to these contaminants including avoiding disruption of ash and wearing proper PPE (personal protective equipment) when in impacted areas. In addition, for people near the impacted areas, keeping surfaces clean of dust and ash and frequent handwashing will greatly reduce potential exposure, according to the Hawai’i DOH.

Who will maintain and monitor the TDS site during construction, operation and closure? Will monitoring information be made available on-line for the public to view?

US ACE and County of Maui will maintain and monitor the TDS site to ensure continued use of compliance with best construction practices and environmental compliance. The County of Maui passed an ordinance (#5596, or Bill 120, 1/21/2024) requiring environmental monitoring and safety measures at the TDS site, with which US ACE and County of Maui Divison of Environmental Management will ensure compliance with. Information and data relating to air quality, water quality, and overall progress will be provided at

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