Three Coal Measure sequences occur in the Hunter Coalfields. From recent to oldest they are:
- Newcastle/Wittingham Coal Measures – Late Permian; and
- Greta Coal Measures – Early to Mid Permian.

Strata and coal seams outcropping in the United area comprise Late Permian Wittingham Coal Measures. The Wittingham Coal Measures are divided into two important coal bearing sub groups, the lower Vane Subgroup and the overlying Jerrys Plains Subgroup. The Joint Venture proposes to extract coal from the Jerrys Plains Subgroup.

In the north eastern corner of CCL775, the Jerrys Plains Subgroup strata dips toward the south west at 3-5 degrees. The uppermost seams of the Jerrys Plains Subgroup (Whybrow, Redbank Ck, Wambo, Whynot) that are mined in the Wambo open cut operations, subcrop to the south and west of the proposed United Open Cut mining area and have limited representation in the United Open Cut.

Open cut mining using a truck and excavator fleet. In the United Open Cut, it is currently proposed that mining will commence in the south eastern end of the proposed mining area and proceed in a north westerly direction. By approximately Year 5 of the operation, the pit will reach the existing United mine infrastructure area and CHPP, which will be decommissioned and removed and the area mined through as the open cut pit proceeds further west.

The approved Wambo Open Cut is currently progressing in a north westerly direction until it reaches the limit of approval in ML1572 from which point it will progress in a south easterly direction. Under the property, mining within the Wambo Open Cut will be undertaken at a reduced rate than previously approved.

There will be some minor changes to the disturbance footprint of the Wambo Open Cut mining area as part of the property, including a realignment to part of the northern boundary of the Wambo Open Cut. This realignment is primarily designed to enable the Wambo Open Cut access to coal seams below its approved mining area which are subject to United mining tenements. Access to the coal seams subject to United mining tenements have been made available as a consequence of the Joint Venture. The realignment and step down to deeper seams will maximise resource recovery within ML1572 and below from A444.

The overburden emplacement areas resulting from the two open cut mines will be combined to provide an integrated final landform across the property open cut mining area. In the early phases of mining in the United Open Cut overburden from the pit will be emplaced over previous open cut mining areas at Wambo. After approximately Year 5 onwards, overburden will be placed back into the United Open Cut void as mining progresses.

Mining operations will be undertaken 24 hours per day, seven days per week.

The United Wambo will utilise the existing Wambo CHPP and coal handling infrastructure (conveyors, stockpiles and train loading facilities) for the washing and transport of coal. No change is proposed to the currently approved operating capacity of the Wambo CHPP and Wambo train loading facility. Both infrastructure facilities will continue to operate seven days a week. ROM coal from the United Wambo will be hauled via internal haul roads to the CHPP.