The operation, over about 35,000ha, will take place at a time around late July when fine weather is predicted, OSPRI operations extension officer Phillip Dawson said.
The aim is to kill possums responsible for spreading TB to cattle and deer. The cattle herds in the area are subject to yearly testing to assess the prevalence of bovine TB.
Consultation with landowners is still happening, to agree the exact boundaries of the operation. Tourist operators, Iwi, hunters, trampers and conservation groups have already been consulted.
The operation will avoid the catchment area for Ōhakune's water supply, and deer repellent will be added to poison baits from the Mountain Rd to Karioi Forest, and to baits dropped on a small area near Pokaka.
The use of repellent will mean a significant reduction in deer deaths, Dawson said.
When boundaries are agreed there will be a pre-feed operation using baits without poison, before the toxic baits are dropped. Landowners will be warned, signs will be put up, and any dogs entering the treated area after that will be at risk.
The last similar operation in the area took place in 2016, and this year's is part of a three-yearly rotation - and not a response to a megamast by beech trees.
But the Conservation Department is involved, because the effects for wildlife are usually profound. Rats and possums eating the baits will die, and stoats eating them will also be killed.
In the past this lack of predators has meant whio (blue ducks) and kererū (native pigeons) have had bumper breeding seasons in the year following an operation.
Mistletoe, rare shrubs and pekapeka (short tailed bats) are also expected to be big winners.
After the operation the results will be assessed by OSPRI, DOC, local Iwi and a research institute. Water testing will form part of the assessment, Dawson said, although there is no risk to drinking water because 1080 is highly soluble and does not persist in water or soil.