Surface soils in the Wangi area and proximate to the surface facilities are classified as part of the Awaba erosional landscape on the Lake Macquarie to Gosford. The Awaba soil landscape is associated with the Munmorah Conglomerate Formation of the Narrabeen Group, and the Newcastle Coal Measures. The topography of this landscape typically comprises low hills with short side slopes and numerous closely spaced drainage lines. Rock outcrops are usually absent and lenses of mudstone and tuff may occur. This soil landscape generally has a high erosion hazard.

Myuna Colliery has extensive workings in the Wallarah, Great Northern and Fassifern seams and has been extracting coal for over 30 years. The area covered by the Colliery is located in the centre of the Newcastle coalfield, a geological sub-division of the North Eastern Sydney basin. The coal deposits of this area are contained within sedimentary rocks of the late Permian age Newcastle Measures. The coal seams typically extend deeper to the south, therefore a higher depth of cover is observed.

Mining activities are concentrated in the Great Northern and Fassifern seams, but could include workings in the Wallarah seam.

The method of extraction for these areas is by conventional underground bord and pillar mining methods. The mining system includes:
- Multiple seam mining – first workings or non caving partial pillar extraction systems where multiple seams are to be mined; and
- Single seam mining – first workings, partial pillar extraction or wide panel full extraction.

Two subsidence zones have been established at Myuna Colliery in accordance with the PA10_0080 (Project Approval).
- Zone A – long term stable mining systems generating up to 20 millimetres surface subsidence (i.e. no measurable or discernible surface impacts) on sensitive surface features including land and seagrass beds; and
- Zone B – Mining Systems generating up to 650 millimetres surface subsidence (under Lake Macquarie).

Mine Infrastructure:
- Men and materials portal;
- Conveyor drift portal;
- Drive houses;
- Up-cast ventilation shaft and fan-house;
- Power Factor Correction Banks;
- Diesel and Oil Tanks; and
- Water storage tanks.

Mining operations:
Myuna Colliery will mine coal in accordance with relevant approvals, licences and guidelines sought through various government authorities. Myuna Colliery will be operating in accordance with the Mining Authority titles ML1370, ML1632 (Mining Lease) and MPL 334 (Mining Purposes Lease) and exploration Leases EL4444 and EL6640 (Exploration Licence). The Planning approval has been given under the Part 3A approval process.

Mine Design:
- The proponent shall ensure that vertical subsidence within Zone A is limited to a maximum of 20mm and that extraction methods are first workings only;
- The proponent shall ensure that vertical subsidence within Zone B is limited to 650mm and second workings are limited to partial pillar extraction within the Great Northern and Fassifern coal seams.

Mining Zone A encompasses all areas of land and shoreline (High Water Control Zone) within the PA area.

Mining Zone B encompasses the area from HWLCZ (High Water Level Control Zone) lake ward within the PA area.

The mining methods will be Place Change Mining, second pass mining and secondary extraction.

ROM coal produced at Myuna Colliery is transferred from the underground workings to the surface CHP via a number of underground conveyors. Coal is initially delivered to the ROM bin and then fed through a primary screen before being transported to a rotary breaker for initial breaking. From the rotary breaker, the coal travels through feeders, screens and into crushers before being loaded into a final product bin. From the final product bin the coal is loaded onto the Origin Energy-owned enclosed overland conveyor and delivered to the Eraring Power Station.

In the event of break downs or servicing of the enclosed overland conveyor, Centennial Myuna temporarily stores coal in a dedicated stockpile area in the north of the Surface Facilities Area.

Coal is recovered from the stockpile by front end loader, loaded onto trucks and dumped into a CHP reclaim hopper for transportation to Eraring Power Station via the enclosed overland conveyor, as required.

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