Maui community mobilizes to protect water quality from runoff after Lahaina fires

Debris from hundreds of buildings destroyed by wildfire in Lahaina, Maui still needs to be cleared. Piles of wreckage sit by the bright turquoise ocean, home to a coral reef where many residents swim, fish and surf.

The community is making a slow recovery from the August 2023 fire, which claimed more than 100 lives. And concerns have been high that the disaster could also damage another valued part of Lahaina: the ocean.

An urban fire of this magnitude has never been seen directly next to a sensitive marine ecosystem. A big question has been: is the water safe?

"It's so hard to answer that," says Liz Yannell, program manager at Hui O Ka Wai Ola, a community-led group that measures water quality. "I'll get people that'll text me and say: my son wants to surf at this beach. Do you think that's safe tomorrow?"

Yannell's group is part of a coalition that mobilized in the wake of the fire to closely monitor the water quality off Lahaina. More than 2,000 buildings burned, including their appliances, plastics, car batteries and other potentially toxic materials. Those chemicals could runoff into the ocean, especially during heavy tropical rainstorms.

So far, the water contamination readings have been lower than expected, leading Hawaii's Department of Health to recently determine the water is safe for recreation. But scientists warn that the effects on a complex marine ecosystem like a coral reef will take years to figure out.

"There's so much that we don't see," says Andrea Kealoha, assistant professor of oceanography at the University of Hawaii at Manoa. "You don't really understand the impacts of anything in one year."

Sampling in the burn zone

Downtown Lahaina's waterfront was once the site of busy shops and residential homes. Every so often, the charred shell of a refrigerator is visible in the debris that remains, hinting at what once was there.

Among the blackened remnants of roofs and walls, there are mounds of silvery ash, even nine months later. After the fire, the Environmental Protection Agency sprayed a glue-like substance called Soiltac to stabilize the debris and prevent it from running off.

"Things are still in piles," says Christiane Keyhani, who works with Yannell at Hui O Ka Wai Ola. "So clearly it seems to have worked, the Soiltac. But if you step on it, it loses its effectiveness."

Every few weeks, a team from Hui O Ka Wai Ola, arrives in the burn zone to take water samples. Yannell and Keyhani put on masks and waders and head to where the waves are crashing. They collect water by dipping a long pole with a cup at the end into the ocean. The samples are then analyzed for the key indicators of water quality, like the pH, clarity, and oxygen levels.

"It's a clear day today in the ocean, but that doesn't mean there aren't concerns," Yannell says. "There were days, especially at the beginning, where it was so brown and turbid."

"This is looking better, which is a good thing," Keyhani says, holding a vial with one of the samples.

Even after the group's lab burned down in Lahaina, staff and volunteers mobilized as quickly as they could to keep up their sampling efforts, aided by a FEMA grant. Their results are supplemented by data from a broad coalition also doing water sampling, including the University of Hawaii at Manoa, the Surfrider Foundation and state and federal agencies.

"There's so much to figure out and it takes all of us coming together to answer all of these questions," Yannell says.

For Keyhani, whose family goes back generations in Lahaina, the work is also a way to support the community in the face of grief.

"I feel incredibly blessed and grateful to be able to sample here," Keyhani says. "It heals for sure. At least I get to be closer to it and have that exposure therapy to the area because it meant everything to me and my family for generations."

So far, worst fears aren't playing out

Urban wildfires produce a broad array of contaminants, especially ones that burn at very high temperatures like in Lahaina. Heavy metals are present in urban infrastructure and in December, officials in Hawaii found Lahiana's ash contained lead and arsenic. The burning process also creates a broad range of "organic compounds'' - only some of which are well understood. One group, known as polycyclic aromatic hydrocarbons (PAHs), are known to be carcinogenic.

So far, water sampling shows higher levels of copper were found at the boat harbor, especially right after the fire. Copper is used in boat paint to prevent marine life from attaching and many boats burned during Lahaina's fire. Still, most contaminants have been lower than the guidelines set for human health, including PAHs.

"There is a sense of relief," Yannell says. "There's still more to figure out, but it's comforting in a way."

For the coral reef, the impacts are less well understood. Corals are highly sensitive animals, affected by cloudy water, pollution from fertilizers and wastewater, and too much sediment running off the land. Kealoha and others at the University of Hawaii have been monitoring the health of the reef off Lahaina post-fire.

"We also see high concentrations of things like zinc," Kealoha says. "And we don't really know what the impacts of zinc are to corals."

Another research team at the University of Hawaii at Manoa is testing for more than 100 organic contaminants, since little is understood about how they could affect marine life at all levels, from tiny microbes to large fish.

"We don't know what's going to be a problem," says Craig Nelson, professor of oceanography at the University of Hawaii at Manoa. "So even if they're not on a list as having a threshold of being toxic to human health, it's still good for us to be able to track them and see how they're changing through time."

Other studies are underway to determine if toxins are accumulating in the fish people eat. Once the contaminants enter the food chain, they become concentrated over time as larger organisms eat smaller ones.

As the ash and debris in Lahaina are removed and the rebuilding process begins, runoff could still be a concern for the ocean. Researchers caution that it could take some time to determine how the coral reef may have been affected, since the effects may be hard to see. Just as the community of Lahaina is experiencing, the true impacts of the fire will take years to understand.

"This is going to be a really long process," says Sean Swift, a Phd student working on water testing at the University of Hawaii at Manoa, who also grew up on Maui. "Beaches are where people bring their babies and their kids and the reefs where people go fishing. And as soon as those things are threatened, I think you have a very strong emotional response."

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