Geological Parameters

The Wintinna Deposit contains up to 3,900 Million tonnes (Mt) of coal resources (based on resource estimates derived from exploration in the 1980s and using the then South Australian Department of Minerals and Energy reporting standards).

The Resources Statement incorporating the results of the 2007/08 field drilling programme shows a JORC compliant resource estimate of 1,287 Mt, of which 837 Mt is in the Measured and Indicated categories.

This resource estimate covers only about 25% of the known area of this deposit.

The coal measures lie within the Permian Mount Toondina Formation (MTF) under 140 to 180 metres of overburden. There are 10 persistent seams in the deposit and 8 main seams with a combined 25-30 metre thickness within a 40-50 metre vertical horizon in the area targeted for open cut mining. They are all generally flat lying with no structural complexities. Weathering of the seams is non-existent.

The Wintinna coal seams generally dip to the North-East at less than 20 (gradient 1:40). In the west of the area the upper seams have been eroded and sub-crop beneath the Mesozoic Sands which dip at less than 10 (gradient 1:20) to the northeast. The Mesozoic Sands consist of the Cretaceous CadnaOwie Formation and the Jurassic Algebuckina Sandstone together forming a poorly consolidated interval of approximately 80 metres thickness. These two formations represent a regional aquifer, which is overlain by the impermeable 60-metre thick mudstone of the Cretaceous Bulldog Shale. A thin veneer of recent alluvium or Aeolian sediments overlies the Bulldog Shale.

The Mesozoic Sands and the MTF contain regional aquifers that need to be dewatered to allow open cut mining (See Project Components - Mine Dewatering).

The terrain is flat and ranges from 120 metres above sea level to 150 metres above sea level.

The typical stratigraphy of the deposit is depicted in the diagram below.

Mine Design/Mining the Wintinna Deposit

Studies by external consultants commissioned as part of the PFS have confirmed that the coal is amenable to economic extraction as a conventional Open Cut and Back Fill operation.

Approximately 2,500 million tonnes of coal are contained within the total deposit at waste to coal ratios of less than 10:1
(bcm: tonnes).

The optimum site for an open cut mine has been determined to be in the North-West sector of EL 4512 within the area of the latest Resource Estimate depicted in the diagram above.

Mine Geotechnical Assessment has been undertaken to Final Feasibility Study detail. A geotechnical model of the deposit has been developed which has determined factors for pit wall slope stability and for the waste dumps.

The Pre-Feasibility studies have indicated that mining will begin with an initial deep box cut which will take approximately 2 years to uncover first coal. Thereafter mining is virtually “steady state” through dewatered overburden and gently dipping, consistent coal seams.

During Stage 1 of the BFS, a number of alternative strategies for the Mining Operation will be investigated and developed to enable selection of a preferred scheme of mining.

The mine footprint after 30 years at 10 Mtpa of coal would be approx 20 sq.kms (10 x 2 kms). Subject to planning and the rehabilitation plan approval this will be back filled, stabilised and replanted to minimize long lasting impact.

Study costings to date have been based on conventional diesel powered excavators and trucks. There would appear to be an opportunity to use electrical powered conveyors to replace some of the trucks with consequent operating cost reduction.

 

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