In a major engineering project, a systematic exploration and investigation of a new site might be carried out and reported on by a consultant specialising in geology, geophysics or engineering (with a detailed knowledge of soil and rock mechanics). However, even when the services of a specialist consultant are employed, an engineer will still have overall supervision and responsibility for the project.
Therefore, the engineer must have enough understanding of geology to know how and when to use the expert knowledge of consultants, and to be able to read theiir reports intellegently, judge their reliability, and appreciate how the conditions described might effect the project.