The drift re-entry is set to officially begin on May 3, and a range of dignitaries, including Prime Minister Jacinda Ardern and deputy Winston Peters, are expected on site that day.
Pike agency chief executive Dave Gawn said most of the staff individual employment agreements were due to end
on June 19.
''They are proposed to be extended to 31 December, 2019. The agency is now preparing the necessary paperwork.''
It had taken longer than originally forecast to get to the point of actual re-entry, so it needed to extend staff contracts to undertake the work.
''And until we do re-enter the drift and ascertain what specific issues we may face, we have made some assumptions about the time it will take.''
The agency is also recruiting for mine workers.
Mr Gawn said it was not putting a number on the recruitment at this stage.
It had 24 fixed-term staff at present, with one appointment pending.
Last year, Cabinet approved additional funding of $14.026million, bringing total funding for the project to $36million.
This includes $3million for the remediation of the mine area before the handover to the Department of Conservation, and a contingency of between 0% and 15% for each area of expenditure.
The agency has also released more information on the re-entry.
It has written to WorkSafe saying it wants to re-establish the 170m barrier prior to full re-entry, and remove the 30m seal to allow vehicle access.
The 170m barrier was installed in 2011, but was replaced with the 30m seal in 2016.
It wants to start breaching the existing 30m seal on April 29.
