But DOC said an aerial application was the most effective way to control pests and using ground-based poisons and traps isn't feasible over such a large, rugged forest.
"Monitoring shows it allows native birds to survive and successfully nest and raise chicks to sustain and build their populations," a written statement from DOC said.
"[Aerial 1080] is the most effective tool we have to simultaneously control three introduced predators over large, remote areas and rugged terrain."
They pointed to scientific research which showed the poison breaks down within 48 hours leaving pests dead and giving native wildlife the chance to re-establish.
But it wasn't just Rivers. Other locals had concerns and met this week in Ngongotaha to discuss alternative ways of using 1080.
Deborah Campbell, also a Mamaku resident, was there.
"I think 1080 in controlled trapping, is fine," she said. "Then the 1080 is not landing on the ground, on plants, on other animals, other interveterbrates or lizards."
Campbell said unemployed people could be paid to lay the bait on the ground.
"We have a lot of unemployed, youth etc. But trapping, fur-trading, that stuff, let's make it some sort of apprenticeship."
The area covers two and a half thousand hectares of bush and DOC uses GPS mapping to ensure accurate coverage avoiding waterways.
Residents said they understood science backed up the use of 1080 - but still, they were not convinced.
The next drop was planned for when there's fine weather, with the aim of protecting the kokakō population in this forest which has seen an increase since the last 1080 drop in 2015.
Made with funding from