The environmental application for the ventilation shaft and an associated access road will service the longwall panels slated for mining at Appin West Area 9.
In assessing its ventilation options, Illawarra said the main difficulty in providing adequate and reliable ventilation to Area 9 was the distance between the proposed underground workings and panels to surface facilities.
“The installation of a new downcast shaft alone would not provide sufficient air flow through the mine due to the large underground distances to the existing upcast shafts,” Illawarra said in its application.
“The installation of a series of smaller ventilation shafts throughout Appin Area 9 was deemed unsuitable due to the unreliability of this arrangement relating to the greater number of surface assets and infrastructure required.
“The construction of several smaller ventilation shafts was also deemed unfeasible due to issues with land access and ownership, location in relation to underground roadways and workings (existing and planned), increased environmental footprint, duration for which it would effectively service the operations and cost effectiveness.”
On using underground booster fans, Illawarra found these would provide just a short-term solution and would be difficult to implement because of the complexity of the workings in relation to clean air roadways and return air roadways.
“Hence, a return booster fan based strategy, with no additional surface facilities, would require nine booster fans and seven main fans (including new main fans on an existing ventilation shaft) and a total installed power of around 5 megawatts underground and 7 megawatts at the surface.
“Although the booster fan proposal would provide ventilation system capacity with limited new surface infrastructure, it would be complex, inefficient and of limited capacity and is not considered an appropriate strategy for Area 9.”
With a new upcast ventilation shaft in Area 9 left as the only option, Illawarra plans to start the construction in June 2011, pending approvals.
Completion is expected to take 18-24 months and includes associated rehabilitation work.
The company aims to blind bore the shaft which ensures no one needs to enter the shaft during excavation.
Blind boring has the drill head completely submerged in water while the attached drill string is rotated from the surface.
The wet slurry from the drilling is vacuumed up and pumped to three associated process ponds.
The shaft will be lined with steel liners known as “collars” which are 5.3 metres in diameter and 3.2m in height.
About 178 of these hollow tube collars are expected to fully line the shaft.
Roughly 3.5 hectares of vegetation will be cleared for the project, including eucalyptus trees that are potentially home to local koalas.
Other threatened animals with a “high” likelihood of occurrence in the project area include the barking owl, masked owl, and three species of bat.
The federal application was made to meet the requirements of the Environment Protection and Biodiversity Conservation Act.
Illawarra recently scaled back its extension project for the Appin and West Cliff collieries.
The BHP subsidiary cut 32% of its mineable coal reserves off the Bulli Seam Operations project which is being assessed by the New South Wales government.
The company completely removed the North Cliff and Appin Area 2 domains in its new “preferred project report” application.
The majority of the Appin Area 3 domain and two longwall panels off the West Cliff Area 5 domain were also removed.
The adjustments remove a lot of the concerns about possible environmental impacts.
They also reduced the total recoverable coal reserve from 306 million tonnes of raw coal under the previous plan to 209Mt.
The Total Environment Centre subsequently claimed the reputation of longwall mining had suffered a “serious blow”