One of the helicopters involved in the poison drop at the Brook Waimarama Sanctuary.

A controversial poison drop in Nelson has turned nasty, with three arrests and a helicopter's fuel supply sabotaged.

Two helicopters and 75 people are involved in the first of three planned drops at the Brook Waimarama Sanctuary, near Nelson. They are spreading bait laced with brodifacoum, a common rodent poison that is toxic to humans and animals. The operation aims to eradicate all rodents from within a 14-kilometre pest-proof fence that was completed last year at the 691-hectare sanctuary, to allow for the reintroduction of native wildlife.

Operation media liaison Angela Ricker said about 11.5 tonnes of bait was expected to be applied during the first drop. The total to be applied for all three drops was 26.5 tonnes.

CHERIE SIVIGNON/STUFF Brook Valley farmer Tamika Simpson says she is very worried about the effects of the poison drop.

"Less bait is required in each of the subsequent two drops," she said.



READ MORE:

* Brook Sanctuary poison drop cleared to go as appeal fails

* 'Sabotage' at Nelson bird sanctuary ahead of poison drop

* Nelson Brook Sanctuary wins High Court ruling on poison drop

* The science and ethics of using poison to protect wildlife in the Brook Sanctuary

Brook Waimarama Sanctuary Trust general manager Hudson Dodd said to hear the helicopters arrive and know the operation was going to start was "a great relief".

"Many of us have looked to this day as a significant milestone in the vision for a pest-free wildlife sanctuary here in Nelson," Dodd said. "All the planning is finally coming to fruition and once this pest removal operation is over, we can look toward the exciting part the project of restoring our native wildlife, including species that have been absent from the hills around Nelson for decades."

MARION VAN DIJK/STUFF A walker last summer wanders through the Brook Waimarama Sanctuary.

The move comes just two days after the Brook Valley Community Group failed in its last-ditch legal challenge to halt the operation. The Court of Appeal on Thursday ruled against the group's bid for a stay of proceedings against the brodifacoum drop.

Ricker said about eight people had been trespassed from the helicopter loading site, the skid site, on Friday night, and someone had drilled a hole in a refill tank, allowing the fuel to drain out. A spill kit was used to contain the fuel and a replacement tank was brought in on Saturday morning.

At 8am on Saturday, several protesters were located at the skid site and police were called. For a time, the protesters blocked the fence track, preventing volunteers from going by vehicle to their positions, she said.

MARION VAN DIJK/STUFF Former Prime Minister John Key closes the gate during a celebration last year for the completion of the fence at Brook Waimarama Sanctuary.

The group was escorted to a 50m perimeter away from the loading site "for safety around the helicopters". Three were arrested and the rest remained on site until the helicopters arrived about 9.15am.

Police said officers were "making inquiries" about the fuel tank.

Farmer Tamika Simpson, whose land is adjacent to the sanctuary, said she was trespassed from the helicopter loading site on Friday evening.

Simpson said she took no direct action, simply stood on the conservation reserve.

"That's probably as direct as I get," she said with tears in her eyes. "I just come as a witness and to try and talk."

Simpson said she was notified of the drop as a direct neighbour on Friday afternoon. Previous notifications had been given 48 hours before any planned drop.

"So, we thought we were working on 48 hours; that's what my family thought with moving stock and everything," she said. "We consider this an illegal operation – the notice is short, the weather forecast is not right and the helicopter loading site, the skid site, is not secure."

However, Dodd said the code of practice required that notice be given to neighbours but "does not define a timeframe".

"At 12pm on Friday, 1 September, we notified the adjoining neighbours of today's drop," Dodd said. "If stock is present in adjoining boundaries, the regulations say we should hand bait within an unspecified buffer inside the fence, which is what we are doing."

Simpson said after she was notified on Friday, she went up to the skid site about 4pm.

"I was a bit shocked that it hadn't been permanently fenced this week," she said. "That would have been what I would have liked for security reasons."

Simpson said she was concerned residents of Brook St had not been informed of the drop.

"So they haven't been given the opportunity to actually move out of the valley if they're worried," she said.

Standing with a group of protesters on Brook St, Simpson said she was born in the valley.

"My father was born in this valley, my family have been here 90 years," she said. "I'm extremely worried. I'm describing it as the darkest day."

Nelson mayor Rachel Reese said she understood the depth of feeling in the community.

"We acknowledge that there are strong views in the community both for and against the brodifacoum drop," Reese said. "It is, however, agreed that increasing biodiversity in our city is extremely important. Nelson City Council continues to support the Brook Waimarama Sanctuary Trust to deliver outcomes to Nelsonians through this ecological restoration project."

A clear ruling had been made by the courts "and so we ask for those that oppose the drop to not do anything that would endanger either themselves or others during the drop process", she said.

Environment minister and Nelson MP Nick Smith hailed the operation as a win for the survival of New Zealand's native birds.

"The Brook Waimarama Sanctuary Trust has fought long and hard for today's pest control operation," Smith said. "It has had to go to court three times ... and three times the court has backed the sanctuary trust."

It was a credit to sanctuary trust members that they had persevered through the court cases and vandalism of the sanctuary to carry out the operation.

"They have toiled for 15 years, raising more than $5 million and spending thousands of hours volunteering to realise their vision and I commend them for their efforts," Smith said. "The science is clear that the only way birds like kiwi, kokako, kea and kaka will survive is to effectively control the pests that have decimated their populations."

Nelson City Council group manager of strategy and environment Clare Barton said the council would be monitoring the drop.



"There are enforcement controls in place and council is communicating with other agencies to ensure the respective roles and responsibilities are carried out to mitigate any negative impacts from the drop," Barton said. "Council will ensure its role in monitoring signage and storage is undertaken robustly."

Ricker said of the 75 people involved in the drop, 60 were volunteers. About 20 were in security roles. Police were also on the scene.

Security gates were in place at the site, about 5km from central Nelson.

Two helicopters would be involved in aerial baiting – one to fly the boundary and the other to fly across the sanctuary in a zig-zag pattern. The pilots held appropriate chemical ratings and had experience in similar pest eradication operations, Ricker said.

The helicopters would be guided by GPS, which would detect any overflies. If any were detected, they would be followed up by boundary checking teams to clear any bait that might be outside the fence.

As well as the aerial drop, bait would be laid by hand within 10m of the fence line.

Hand baiting teams had practised broadcasting bait before the operation to ensure sound technique, Ricker said.

Under the code of practice, all bait must be dropped within the pest-proof fence.

"To ensure that this happens, volunteers will be positioned along the outside of the fence to monitor the boundary throughout the operation to check if any baits fall outside the fence," Ricker said. "If baits are found, they are thrown back inside the fence. At the end of the day, the entire perimeter is again inspected and signed off as clear."

In preparation for the poison drop:

* The fence was inspected by an independent expert on June 1 and August 11 and had been signed off as ready for the aerial operation;

* the pest-proof swales and culverts had been closed, locked, inspected and signed off as ready for the aerial operation;

* a bait screen across the dam was in place to prevent pellets from travelling downstream if they fell into the Brook Stream;

* neighbours had been notified;

* Nelson Marlborough Health had been notified;

* veterinarians were on-call in the "highly unlikely" event of a domestic animal poisoning.

The baits were cylindrical pellets, about 10mm long and dyed green.

People should not touch the bait, watch children at all times, refrain from eating any animals from the area and keep dogs on leads at all time and away from any animal carcasses.

Nelson city councillor Tim Skinner said he was disappointed at the short "less than a day" notice.