But just a year after they bought the property, a coal exploration lease was granted over the property, and in 2003 Bulga Coal submitted a development application to longwall mine under the vineyards.
For Xstrata it was too good an opportunity to miss. Mining underneath the vineyards, and ultimately the Kennedys’ house, meant they could extend 30 longwall blocks, add an additional 20 million tonnes of coal to their reserve base; and ultimately realise additional potential revenue of $700 million.
On a company level for Xstrata Coal and the Beltana team, successfully handling and communicating with the Kennedys and the wider community were essential for the livelihood of the mine. In the big picture, however, the success of this project could do a lot for the community’s perception of longwall mining and the industry as a whole. Get it wrong, and it could mean a lot of damage beyond the Kennedys’ property.
In 2004 the development application was approved, and after much deliberation, the Kennedys decided to pursue their dream and build their retirement home.
Beltana assisted the Kennedys by having their mine subsidence engineering consultants review the design of the house. According to the consultants, the original design of the house had “serious flaws”.
The original design did not provide a mechanism to allow the house to move horizontally or vertically, meaning the house would have been pulled apart by its piers.
Together with the Kennedys, the consultants revised the house design, which was subsequently approved by the Mine Subsidence Board. The 65m-long house was constructed in 2003-04 on the 38-hectare property.
Under the risk management plan, Beltana expected about 1.5m of subsidence and engineered the dwelling – including constructing the house on piers and a steel cradle – to withstand the subsidence impacts. The house would be incrementally jacked to keep it in a plane as subsidence occurred, and allowed to slide off specially designed plates between the piers and steel cradle.
Testing of the design began in mid-2005 when Beltana commenced longwall panel 5. Numerous aspects of the Kennedys’ vineyards were monitored including trellis tension, irrigation, soil moisture, yield, grape sugar levels and satellite infrared imagery was used to watch vine vigour.
To monitor the house, which was undermined in May/June 2006, the Beltana team pegged out the house dimensions and piers, which were then surveyed on a daily basis and the results analysed by subsidence consultants.
Beltana environment and community coordinator Ralph Northey said by jacking the house, it was able to be kept on a plane with about 600mm difference corner to corner at times.
He said only cosmetic damage to the house was observed during and after the undermining, which the Mine Subsidence Board and the Kennedys were now working together on to repair.
The Kennedys’ residence will not be undermined again for a further 14 years and the couple can live their lives with minimal disturbance from the mine.
For Beltana, it found the key to success was early community engagement and getting the Kennedys involved in the decision-making process for the development of the Private Property Subsidence Management Plan.
All of the efforts to minimise the impacts of subsidence for the Kennedys and their property have been worthwhile, as in a small way the equilibrium of the community has been maintained.
Published in the March 2006 American Longwall Magazine
