One of the principal uncertainties in geotechnical engineering is the risk of encountering an unexpected geological condition. This is because geological materials are often irregularly arranged and highly variable in their material and mass properties. Failure to anticipate site ground conditions generally results from an inadequate geological understanding. The paper presents an approach to site evaluation designed to assist anticipation of geological conditions, from desk study to project construction, that is based on developing an understanding of the total geological history of the site and its environs. The premise of the paper is that the conditions and geotechnical characteristics of the ground are the product ofthe geological and geomorphological history ofthe site, including past and present climatic conditions, in short, its total geological history. The engineering performance ofthe site results from the influence ofthe engineering works on the total geological history. The object of the paper is to show how knowledge of the geological environment aids anticipation of the site ground conditions by development of a preliminary engineering geological model which guides the planning of the investigation and the design and construction of the project. This model develops progressively to be site specific, as the understanding of the local geology improves during the development of the project. The approach starts with an initial series of simple, related, geological and geomorphological models to generate questions that should be asked about the site and to provide the basis for making a check list. The models presented in the paper represent the end members of a continuous range of possibilities. The geological concepts embodied in the selected initial models and the specific check lists made for the site are then investigated thoroughly as the site specific engineering geology model develops during the project studies.

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