The Electricity Trust of South Australia is presently concerned to procure a suitable site for a major substation to the south of Adelaide, and a number of alternative sites are under consideration in the country immediately east of Happy Valley Reservoir and also further east in the hills to the south and the northeast respectively of Cherry Gardens. An approach has been made to the Mines Department by the Electricity Trust for geological assistance in appraising the relative merits of the various sites, particularly in respect of foundation conditions and costs of levelling and general foundation preparations. The following notes record geological observations and conclusions resulting from this inspection.