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Honolulu Civil Beat – Maui Mayor Gives EPA The Go-Ahead To Seal Down Lahaina’s Toxic Ash With Soiltac (TPD2310017)

Maui Mayor Gives EPA The Go-Ahead To Seal Down Lahaina’s Toxic Ash With Soiltac®

Public debate over the soil-stabilizing product’s use has been swirling as county officials, environmentalists and scientists weighed its pros and cons.

By Paula Dobbyn

October 9, 2023

Reading time: 8 minutes.


With the rainy season approaching and Lahaina students poised to return to class next week, a sense of urgency has grown over how and when to temporarily glue down tons of toxic ash from the August wildfires that consumed the West Maui town.

In recent days and weeks, local elected officials, an independent scientist, environmentalists and others have wondered whether a soil stabilizer called Soiltac should be deployed as the Environmental Protection Agency has recommended to the county.

On Monday evening, Maui Mayor Richard Bissen gave his approval.

Maui Mayor Richard Bissen decided Monday to let the EPA use Soiltac in Lahaina to temporarily seal down potentially toxic ash. (Kevin Fujii/Civil Beat/2023)

“It’s important to protect our community and our air quality and ocean waters from the harm that ash and debris can bring,” Bissen said in a news release. “With EPA’s review of the product and its recommendation, along with understanding that if we do nothing we will be placing our people and environment at risk, we will proceed with the application of a soil stabilization product.”

With Bissen’s approval, Soiltac can be applied on Lahaina’s burned buildings in about a week, said EPA spokesman Rusty Harris-Bishop. It’s expected to take a month to cover all the surfaces that need to be sprayed and some areas will need more than one coat, EPA officials said.

Spraying will begin for properties in re-entry zones and extend to remaining burned areas, according to the mayor’s news release. Areas close to shorelines will be prioritized to minimize the risk of potential ash and debris runoff into marine waters, the release said.

There’s widespread agreement that something needed to be applied to hold the ash in place before clean-up crews from the U.S. Army Corp of Engineers can remove the contaminated rubble with heavy equipment.

If the ash becomes airborne or is washed into the ocean or aquifers, it could expose humans, fish, seabirds and other organisms to cancer-causing agents and potentially cause chronic and acute health problems, government officials have cautioned.

The EPA had recommended that Soiltac be sprayed on the footprint of burned structures on approximately 128 acres in Lahaina, a fraction of the estimated 2,170 acres that the Aug. 8 fire incinerated, killing at least 98 people in the process.

Maui County officials are weighing whether and when to apply Soiltac to temporarily hold down potentially toxic ash from parts of Lahaina. (Ku’u Kauanoe/Civil Beat/2023)


The agency had asked Maui County to give it an answer by Sept. 28 but no answer was forthcoming.

On Monday morning, the mayor’s communications team said by email that the administration had reached no decision on the use of Soiltac in Lahaina, “nor a timeline for a decision that we are able to share at this point.”

Then Monday evening the county sent out a press release announcing the mayor’s decision.

Soiltac is basically a liquid plastic that coats an area with a thin, clear crust, trapping dust and ash by holding them down.

The product’s transparency allows remediation workers to see what’s underneath and decide how the debris should be handled and disposed of, depending on its potential toxicity.

An EPA hazardous waste removal team sprayed Soiltac on burned property in Kula in September. (Courtesy: EPA/2023)


With Maui County’s approval, the EPA used Soiltac in Kula in late September following the Aug. 8 wildfires that destroyed 19 homes in Upcountry Maui.

The EPA considers Soiltac a nontoxic substance based on published studies and a review of the manufacturer’s proprietary formula. Its effects, if any, should the product wash into the ocean onto coral reefs have not been tested.

People who expressed concern about the use of Soiltac said it’s hard to know if the product is safe without knowing what’s in it and knowing how it interacts with the environmental conditions present in Lahaina.

West Maui County Councilwoman Tamara Paltin said she sent a letter to the EPA last month with a list of questions and concerns about Soiltac to which she said the federal agency did not respond. Over the weekend, she tried again, reaching out to Peter Guria, EPA regional incident coordinator for the Maui wildfires.

The answers she received from Guria left her dissatisfied. EPA said Soiltac is not biodegradable while the product’s website says that it is, Paltin noted.

One major concern Paltin and others have is what happens if the polymer-based product breaks down and enters the environment before the Army Corp of Engineers removes it along with the ash and debris. Will micro-contaminants wash into marine or freshwater environments or be released into the air?

EPA doesn’t think so.

“In the event that Soiltac is disturbed, either through foot traffic or other physical disturbance, EPA does not anticipate that the ‘crust’ can break down into particles small enough to be considered a microplastic issue,” Guria told Paltin in an email.

Even if a small amount is released, that’s way better than any largescale release of ash to the reef or air, Soiltac proponents say.

Paltin and East Maui Councilman Shane Sinenci went to the top of EPA’s chain of command with a five-page letter to EPA Administrator Michael Regan on Friday, outlining a list of detailed questions about Soiltac.

They received a letter back from Regional Administrator Martha Guzman saying the agency would only move forward with the application of Soiltac if key partners, including Maui County, are supportive and concur. She also mentioned that she’ll be on Maui later this week and would like to meet with the two council members.

West Maui County Councilwoman Tamara Paltin had a list of questions and concerns for the EPA over its proposed use of Soiltac to control the potentially toxic ash in Lahaina. (Kevin Fujii/Civil Beat/2023)


Craig Downs, an independent ecotoxicologist, said EPA’s recommendation to use Soiltac is based not on scientific data but on the company’s marketing claims.

EPA officials push back on that notion saying Soiltac has been successfully used in a variety of environmental remediation projects throughout the country.

Soiltac was applied at the Alameda Point Superfund Site in San Francisco Bay. And San Mateo County is using the product in California to create and maintain a bicycle park close to the shoreline of Half Moon Bay.

At a Maui County Council meeting Wednesday, Soiltac’s manufacturer testified and insisted his product is safe. Chad Falkenberg, chief executive of Arizona-based Soilworks, said the spread of misinformation and what he called conspiracy theories about Soiltac are disheartening and dangerous.

Falkenberg declined an interview request.

Paltin noted that schoolchildren will be attending class about a quarter-mile mauka of the burn zone. Something urgently needs to be done about controlling the ash but Paltin said she isn’t convinced Soiltac is the answer.

“Obviously, I would prefer something that’s organic,” she said in an interview Monday morning. “We definitely need a solution before schools start because you can’t control the wind.”

After Bissen’s decision came out Monday night, Paltin said she concluded, after speaking with EPA officials for two hours in the afternoon, that she was “unable to make an informed decision to support or not support based on the lack of information” about Soiltac’s proprietary formula and how the tackifier will degrade over time.

She advised anyone visiting the burn zone to wear appropriate protective equipment, including a P100 respirator.

Lahainaluna High School is set to reopen Monday, followed by Lahaina Intermediate on Oct. 17 and Princess Nahi’ena’ena Elementary on Oct. 18.


With the county’s approval Monday, the EPA will apply a soil stabilizer called Soiltac to control potentially toxic ash in Lahaina from washing into the ocean. (Ku’u Kauanoe/Civil Beat/2023)


Several nonplastic alternatives to Soiltac exist. Some are resin-like and sticky. The downside is they can trap household pets, birds, insects and wildlife.

The EPA considered alternatives but ruled them out for that reason, said Kelly O’Neal, unit leader for the EPA’s environmental response team for the Maui fires.

A group of some 70 scientists and environmental activists who have been meeting regularly about the Maui wildfire response and recovery seemed on Monday to be leaning in favor of Soiltac’s use because of the public health implications of leaving the ash untreated any longer.

Kihei-based environmental scientist Robin Knox has weighed the pros and cons and said she has come down on the side of using Soiltac because action needs to happen sooner rather than later.

“There may be some small environmental risk from the product, but it is certain to be an environmental disaster with huge risk to human health and the environment if the ash is not contained somehow,” Knox said Monday.

Read Paltins and Sinencis Sept. 6 letter to the EPA below, along with EPA Regional Administrator Martha Guzmans response.

 Civil Beats coverage of Maui County is supported in part by a grant from the Nuestro Futuro Foundation.


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About the Author

Paula Dobbyn

Paula Dobbyn is a reporter for Civil Beat based on the Big Island. Reach her at pdobbyn@civilbeat.org, 808-983-9405, or @pauladobbyn on Twitter.

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