Government to fund Pike River re-entry plan

  • Simon Bridges
Energy and Resources

The Government has approved conditional funding of a staged plan to re-enter and explore the main tunnel leading up to the rock fall at the Pike River Coal Mine, Energy and Resources Minister Simon Bridges has announced.

The decision follows approval in principle of the re-entry plan risk assessment by the Solid Energy Board.

Mr Bridges said the Government will fund the estimated cost of the plan, at $7.2 million.

“Our criteria are that any re-entry into the tunnel up to the rock fall is safe, technically feasible and financially credible. Safety is paramount, and the High Hazards Unit of the Ministry of Business, Innovation and Employment has reviewed the plan and is comfortable with it,” said Mr Bridges.

“This is a highly complex and technical operation and it will be carefully managed in stages, with a risk assessment undertaken at each stage. Ensuring the safety of workers is an absolute bottom line for the Government and Solid Energy.”

Mr Bridges said the scope of the operation did not include entry into the main mine workings which is blocked by the rock fall. 

“The Government cannot comment or speculate about re-entering the main mine until the tunnel re-entry has been successfully achieved,” Mr Bridges said. 

Questions and Answers

What are the stages of the re-entry plan?
A risk assessment will be undertaken at the end of each stage, before proceeding to the next stage.

After the first stage of sealing the ventilation shaft is completed, the Solid Energy Board also intends to carry out a risk-based approach for its approval for the remainder of the re-entry plan.

Stage One

  1. Plug the top 50-60m of the 100m deep ventilation shaft to ensure full control of the mine atmosphere.  Constructing an effective plug will require the placement of up to 700 cubic metres of concrete and other material.

Stage Two

  1. Drill new boreholes into the top of the main tunnel
  2. Use a camera to check tunnel in area where a second plug will be placed
  3. Place expanding foam seal known as ROCSIL into the tunnel via a borehole from the surface. This will form a plug at approximately 2.3km into the mine, and about 40m on the portal (eastern) side of the rock fall that prevents entry into the main mine workings.
  4. Pump inert nitrogen into the tunnel area between the ROCSIL plug and the rock fall, which will prevent fresh air from reaching the inner mine.  This will remove the risk of any fires re-igniting in the mine.
  5. Ventilate main tunnel from the portal up to ROCSIL plug

Stage Three

  1. Once the tunnel is ventilated, trained mines rescue personnel will enter and explore the tunnel. Police will review information that comes out of the mine.

Why is the decision to fund the re-entry conditional?
The three conditions for any re-entry into the tunnel up to the rock fall are that it will be safe, technically feasible and financially credible throughout the process.

The work will be subject to continuous review by all parties as it progresses. This is to ensure safety requirements are met and risk assessments throughout the project remain acceptable.

Will the plan change at all throughout the process?
Small variations to the current plan may also be needed depending on the success of each stage of the operation. Any major changes would require all the parties to again reassess the three conditions.

When will the work begin and how long will it take?
The work is weather dependant and it is hoped it will start in October. The duration of the work will depend on how each stage proceeds.