The Denniston Plateau is a north west dipping plateau bounded to the west by the Papahaua Overfold / Kongahu Fault zone, and to the east by the Mt William Fault.

The coal measures consist of a fluviatile sequence of fine to very coarse sandstones, siltstone, mudstone and coal seams.

The main coal seam varies in thickness from less than 1m thick up to 14m thickness locally.

Depth of cover varies from 0m at outcrop to over 150m at the eastern margin of the Mt William Fault. Inferred and Indicated resources include coal up to 130m below surface, while the measured resource includes coal up to 75m below surface.

The deposit roughly covers a 6.5km by 4.5km area. The model is bounded by the Escarpment Fault to the south, the Waimangaroa Gorge to the north, and the Mt William Fault to the east.

The Escarpment mine utilised truck and shovel for waste and coal movement. The operations are supported by additional equipment including dozers, graders and water carts.

Mine design blocks are applied to the in-situ resource model to generate the raw reserves used to create a separate mine reserve model.

The mine model also reflects working sections or seam aggregations, mining methods and associated loss and dilution impacts. The mine reserve model is used as the basis for Ore Reserves reporting.

Escarpment is a mine project that is currently in care and maintenance. The reportable Ore Reserve is based on the life of mine plan. It has been determined the mine plan is technically achievable and economically viable, and that material modifying factors have been considered.

Pit optimisation runs were completed to determine economic pit limits using BRL supplied cost and revenue data.

Coal loss and dilution factors are also applied and vary by the equipment type uncovering the various coal seams (i.e. excavator size). Roof and floor coal loss thickness is set at 10cm and roof and floor waste dilution thickness ranges from 0cm–5cm.

Seam aggregation logic pre-determines what is defined as mineable coal by applying working section tests based on minimum coal thickness of 50cm, and a maximum raw ash of 30% on an air-dried basis.

The ROM coal produced at Escarpment is not washed resulting in 100% yield for the operation.

Product coal specifications include ash, sulphur, moisture and calorific value.