Civil engineering projects start with intensive site investigations to evaluate the appropriateness of the geographic location to the intended construction. This process is lengthy and crucial to the success or failure of the project. Personnel with multiple skills are required at the evaluation stage, including experts in soil mechanics, geology, surveying, management, structures and meteorology. However many less fortunate parts of the world lack such expertise and cannot afford it. The main objective of the research described in this paper is to develop an expert system that will use images from different sources to assess sites for civil engineering works. Five engineering applications have been selected for this research. Certainty factors for uncertain or incomplete information are presented. A frame-based expert system is developed and tested in this research. Three different tests have indicated that the system is accurate and promising for site investigations.