The council became aware of the risk of a 35-metre sinkhole opening beneath the headframe when high rainfall in June caused a collapse in the Hart Shaft.

The repair plan has required advice from experts on the mainland and changed a number of times to find the best solution.

West Tamar Council general manager Rolph Vos said a conveyor was on the site which had been tested and was ready to commence work this week.

“We have been filling the surface voids so there is a flatter area to work on and also so that vibrations that might occur can assist in making sure that all that area is filled,” he said. “The conveyor is so we can use a front-end loader to put the gravel onto and it will run horizontally into a funnel and then go down the pipe.”

The area around the pipes, that will be used to fill part of the mine shaft, has been cleared and the headframe has also been prepared ready for a drill rig to arrive.

“We are expecting the drill rig to come in around the middle of May and it will be set up to run down the pipe and cut the pipe at the right level in the shaft,” Mr Vos said. “The plan is to run the material down the pipe, let it fall down the bottom of the hole and once we get to the right level then cut the pipe off, because the pipe runs further into the ground than where we want to fill to before we insert the first concrete plug.”

Mr Vos said the council had hoped to see the mine being filled sooner but he was confident the work would be carried out in sufficient time to avoid a further problem.