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Brook Waimarama Sanctuary Trust Brodifacoum Drop FAQs

Council has received numerous questions relating to the Brook Waimarama Sanctuary Trust's Brodifacoum Drop. The following has been put together to provide a response to those questions.

Consent Process

Resource consents for the use of hazardous substances and for the aerial discharge of brodifacoum were granted in 2016.

The requirement for a resource consent for the discharge of brodifacoum inside a predator-proof fence was removed by the Government introducing the Resource Management (Exemption) Regulations 2017.

The Council accepted the Trust's application to surrender its resource consent for the aerial discharge of brodifacoum within the predator-proof fence under the Regulations.

Resource consent for the use of hazardous substances is still required and remains in place.

Relevant landowner approvals under both the Resource Management Act and Reserves Act are in place.


The Council is not the organisation undertaking the activity. The Brook Waimarama Sanctuary Trust is responsible for the activity. Council understands that for the first drop, the Trust placed notices in the newspaper and contacted adjoining landowners directly.

In relation to notification under the RMA, the Regulations require the Trust to give notice to the Council at least 48 hours prior to a drop. The Regulations do not require notification of other parties.

The Trust is also required to provide notice, including to the public and adjoining landowners, under the Code for using brodifacoum. The Trust has advised the Council that it has and will continue to comply with these requirements. The Ministry of Primary Industries is the lead agency concerning compliance with the Code.

The Trust should be contacted directly for further information on future drops.

Trespass Notice

Nelson City Council has powers under the Reserves Act to take action under the Trespass Act 1980 and to authorise others to act under its authority.

An occupier under the Trespass Act includes those authorised by the Council, e.g. the Trust.

Nelson City Council respects rights to undertake lawful protests. Some limitations on these rights are justified to ensure the safety of persons and property, and the proper management and control of land the Council administers.

The Council has worked and will continue to work with parties to resolve particular issues arising from the first drop and to attempt to reach agreements for reasonable access arrangements for any future drops.

Loading Area

The Trust's resource consent application included using the reserve adjoining, but outside of, the predator-proof fence for loading the helicopter during the aerial operation

The consent for handling hazardous substances was granted and remains in place (the Exemption Regulations only apply to activity inside the fence). Loading baits does not require a discharge consent.

The Council has also provided landowner authority under the Reserves Act for the Trust to use this land. This includes short-term restrictions on public access and is provided for in the reserve management plan.

Control of the location of the loading area rests with the Trust during the operations.


Council contractors were on site to monitor the operation including signage.

The Trust complied with landowner and resource consent requirements regarding signage on the boundary of the site.


The predator proof fence is fit for purpose. This has been confirmed by the High Court.

The Court considered evidence and submissions about the fence from the Trust and the Brook Valley Community Group before arriving at that decision.

The control of the helicopter loading site is a matter for the Trust and for relevant agencies.

Fencing required under the Code for using brodifacoum was in place during the operation.

Fuel Spill

As a result of a hole being drilled by unknown persons in the fuel tank, there was a fuel spill at the skid site. When the spill was detected the fuel had already penetrated into the ground and there was little visible on the surface. The police have been notified.

The spill has caused significant environmental contamination and potential breaches of the Resource Management Act 1991 and the Reserves Act 1977. An independent review is currently being undertaken on the effects of the spill. The outcome of that review will determine what further action is required.

Findings of the Fuel Spill Investigation

The Council investigation on the fuel spill incident that occurred during one aerial drop operation is now complete.  The conclusions reached and action to be taken are as follows:

(a)  There is a duty to have fuel stored in a safe and appropriate manner.  Sufficient precautions were taken and there is an absence of fault given the incident was a consequence of reckless and criminal actions of unknown persons.  A letter has been sent to the Trust advising that security for any future fuel storage should be reviewed.

(b)  The site has been listed as a contaminated site on Council’s HAIL register.

(c)  The immediate site of the spill is contaminated.  Samples show low levels beyond the immediate site.  Expert advice recommends leaving the site as it to assist with hydrocarbon evaporation.  The Trust is required to have a specialist undertake ongoing monitoring to track recovery of the site and surrounds.  

Dust and Other Effects

The brodifacoum being used is in a hard waxed pellet form at a concentration of 0.002%. Negligible (if any) contaminated dust is generated. The active ingredient is sold over the counter to the general public at a greater concentration of 0.005%.

Independent environmental experts and public health officials have provided advice on the operation. That advice is being complied with. The effects, including for the loading site, were assessed through the resource consent process.

The High Court stated: "Here [for the Brook Sanctuary], the risk regarding the use of brodifacoum has been assessed many times by a variety of different departments, agencies, council planners and scientists as acceptably low when used with appropriate constraints. I have not been persuaded by my review of the affidavit evidence that this risk assessment is so wrong as to be untenable."

Dust is being monitored on site. Pre- and post-drop sediment and water quality monitoring is being undertaken.

The Environmental Protection Agency assessed a complaint of brodifacoum dust exposure at Brook Valley Camp Ground and found it "extremely unlikely" that any exposure occurred and attributed it to pollen and dust generated by helicopter rotors.

Alternative Options

Suggestions have been made about alternative controls, e.g. trapping.

These alternatives were explored by the Trust and the decision on brodifacoum was the Trust's decision. Evidence concerning the assessment of alternatives was provided to the Independent Commissioner as part of the resource consent process and more recently in evidence before the High Court.

Workplace Safety

Worksafe New Zealand has been notified of the operation and it is primarily their and the Trust's responsibility to manage on-site health and safety matters. The Council is being advised of the outcomes of any incidents that were reported.

Monitoring for Brodifacoum Residues

  1. The sampling was done by Cawthron on behalf of Nelson City Council, according to a protocol advised by Cawthon and the Landcare Research lab in Lincoln who do the testing.
  2. Sediment samples were collected at three lower Maitai sites on 19 August at the same time as water samples were being taken – these are samples 212243, 212244 and 212245
  3. Sediment samples were collected at four Brook Stream sites and Normanby Bridge (21242) on 24 August. The Brook Stream sites were:
    Within the sanctuary, upstream of the 1905 dam (21238)
    Below the 1905 dam and upstream of the campground (21239)
    Upstream of the Cummins Creek confluence (21240)
    Just upstream of Dommett St in the Brook Stream (21241)
  4. The first Brodifacoum drop occurred on Saturday 2 September.
  5. Sediment samples were collected on Sunday 3 September and Monday 4 September at the four Brook Stream and Normanby bridge sites, but these have not been tested.
  6. Sediment samples were collected 7 days after the first drop on 9 September at the four Brook Stream sites (21246, 21248, 21249, 21250), the Normanby Bridge site (21251), and an additional site within the Sanctuary at the 1905 dam grid (21247) and these have been tested. All results are below method detection limits. Additional sediment samples were collected 1 month after the first drop ( Fri 6 Oct 2017, which was also 1 day after the second drop), and the last sampling was done two months after the first drop. 

As at 24 November 2017 all samples have now been tested. All results are below method detection limits. You can download the results here.


Monitoring Operations

The Council had a monitoring officer on-site for all three drops. The requirements of the Resource Management (Exemption) Regulations 2017 Schedule 2, resource consent conditions and Nelson Resource Management Plan permitted standards were met (apart from the fuel spill).

MPI audited operations for compliance with the code of practice on the third drop and raised no concerns.

A guide for bait application best practice states a weather forecast of at least 72 hours without rain of more than 10mm is best but also acknowledges that expert input is required for each site and operation. The Trust have advised the Council that its experts do not anticipate any significant impact on the effectiveness of the operation arising from the rainfall that occurred within the 3 days of the second drop.

Downloads and links