Olive Downs South
Alluvium and semi consolidated sediments consisting of sand, clay and gravel cover the deposit area. This material is described as Tertiary but a component of it is likely to be Isaac River Quaternary sediments. Tertiary/Quaternary sediment thickness increases towards the south. Average depth of Tertiary is in the order of 45 metres ranging from 0 to 90 metres.

Willunga
In the Willunga area the average depth to the base of Tertiary is in the order of 20 metres ranging from 0 to 70 metres in the resource area. The thickness of Tertiary does not seem to be related to the current river location. There does not appear to be any clear relationship between the Tertiary depth and the structure of the areas. There are no indications of any surficial basalt in either Olive Downs South or Willunga.

Weathering
Olive Downs South
Average depth of weathering is in the order of 65 metres ranging from 20 to 80 metres. Comparison of depth of weathering with depth of Tertiary indicates almost no consistent relationship, however both increase to the south.

Willunga
Average depth of weathering is in the order of 60 metres ranging from 20 to 100 metres. There appears to be a broad relationship between the depth of weathering and the structure of the area - the deeper weathering occurring in the syncline.

Coal seams
Olive Downs South
The Leichhardt and Vermont Seams of the RCM form the principal econom ........

The summarised mining sequence will follow a process that is generally common to other surface coal mines:
- Clearing and topsoil stripping ahead of the mining operation will be carried out progressively, with a practical minimum of disturbed area maintained ahead of mining. Topsoil will be stockpiled for later rehabilitation;
- The weathered upper waste areas are expected to be free-dug, using scrapers, excavators and trucks, without the need for drill and blast operations;
- Competent waste material will then be drilled and blasted below the free-dig zone, and removed in benches ahead of coal mining, using excavators and trucks assisted in part by dozers. Waste material will be placed on in-pit and ex-pit dumps as required. As much waste as possible will be placed back in-pit. The mine design also allows for waste to be dumped into adjacent pit areas;
- Coal will be mined using excavators, front-end loaders and trucks, with the ROM coal trucked to a stockpile adjacent to the CHPP;
- The waste dumps will then be rehabilitated by reshaping and the stockpiled topsoil will be placed onto the reshaped dumps. Revegetation completes the mining process. This will happen progressively as the mining operation advances.

Both the ODS and Willunga domains include geographically extensive subcrops, and the mining strategy used is to progressively extract coal down from the subcrops, opening new areas along strike as necessary to maintain the required p ........

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