The Lock Coal Deposit is located 15 km west of the town of Lock, on Eyre Peninsula in South Australia. It contains both Tertiary and Jurassic coals, although neither have been fully delineated. Measured reserves of in-situ Jurassic coal are 260 Mt. The Tertiary coal is poorly defined with measured reserves of 60 Mt. Because of this, and due to its proximity to the Polda freshwater pumping station, the Tertiary coal was not considered in this study. The Jurassic deposit consists of numerous bands of high ash coal of varying thickness and quality, interspersed in a carbonaceous zone varying from 6 to 32 m thick. Overburden thickness varies from 35 to 230 m, and consists predominantly of poorly consolidated and silty sands. There are two saline aquifers present: one above and one below the coal zone. Evaluation of the deposit is at an early stage. For the purposes of this study major assumptions were necessary with respect to coal beneficiation, overburden geotechnical parameters, dewatering aspects and power station coal requirements. It is our opinion that it would be practicable to mine coal from the Lock deposit to fuel a major power station. A mining system combining draglines for overburden removal and shovels and trucks for coal mining has been selected for this study. A 750 MW capacity power station would require 114 MT of Lock coal for a life of 37 years with a peak requirement of 4.1 MTPA. This was estimated to be the maximum capacity that could be supported by the deposit at this stage of its evaluation. The capital required to bring the mine into operation is $352 M, to be spent over a six-year period. Subsequent and replacement capital expenditure would be $116 M, to bring the total capital required for the project to $468 M. Operating costs at peak production would be $12.55 per product tonne. Mining as proposed would utilise 114 MT of coal at an average dry ash content of 35%. This is equivalent to 44% of Measured geological reserves, and is 65% of coal having a strip ratio less than 10 bcm/t. It is estimated that about two years of further drilling and evaluation would be required before a decision could be made to proceed with the project. A construction and pit development period of four years would be required following the decision to proceed, before the first coal was produced.