West Tamar Council to vote on new repair method for Beaconsfield Mine

The West Tamar Council will hold a special meeting on Tuesday to discuss the new strategy which was originally out-of-reach with an estimated price of more than $2 million.

The Hart Shaft partially collapsed about 47 metres below the surface after high-levels of rainfall in June, which allowed saturated ground material to flow into the open shaft.

The soil blocked the shaft and cracking is visible at the surface which could undermine the iconic headframe and skyshaft structures.

The council’s Infrastructure Services Manager Ian Howard said the best fix is to fill the shaft with a fine quarry product via the two existing steel rising mains, which would be cut open at the 100 metre level.

“Once the shaft is filled from the bottom at [minus] 415 metre up to this level where there is a substantial structure know as the kingset, a thick concrete plug will be poured, again via the rising main pipes,” he said.

“At 100 metre the shaft is in competent sandstone and this plug is unlikely to ever move. The shaft can then be filled to the surface which prevents surrounding soft clay material from entering the shaft and allowing further surface collapse.”

Mr Howard said the estimated cost was $1.2 million which includes plugging and filling the shaft, remediation work on the mine yard, headframe and skyshaft plus professional services.

“A little over $200,000 has already been spent which brings the likely final cost into the $1.4 to $1.5 million range,” he said.

“Following this work it is likely the areas of the mine yard will still suffer from minor surface failures and subsidence for some years as smaller underground voids collapse and this will need to be carefully managed to reduce public risk.”

The federal government will fund half of the costs under the National Disaster Relief and Recovery Arrangement, and the state government and West Tamar Council will each foot 25 per cent of the bill.