When a firestorm consumed the Hawaii town of Lahaina last year, killing 100 people, it left behind a toxic wasteland of melted batteries, charred propane tanks, and miles of debris tainted by arsenic and lead.

Crews have already removed some of the most hazardous items, shipping them out for disposal on the mainland. Now begins the even more formidable task of collecting hundreds of thousands of tons of additional debris and soil — enough to cover five football fields about five stories high. Even as excavators began filling dump trucks this month, the question of where it should all ultimately go remained unanswered.

For now, the county has chosen a “temporary” dump site in Olowalu, a few miles south of Lahaina on the West Maui coastline. There, just up the hill from a vital coral reef and an important ecosystem for manta rays, residents worry that dumping dangerous waste into the area could create a fresh disaster.

“It hurts,” said Foster Ampong, 65, who has family members who lost homes in Lahaina and spends much of his time in Olowalu helping other relatives farm taro. “I’m very much worried about the future of Olowalu.”