This manual provides RIDOT engineers with clear and concise guidelines for understanding, planning, conducting, and evaluating geotechnical site investigations in Rhode Island. The advantages and disadvantages of both standard and specialized site investigation techniques are presented. Correlations between in situ test results and engineering properties of soils are also presented. The guidelines focus on the specific soil conditions found in Rhode Island as well as the size and scope of geotechnical investigations that are necessary for different types of structures commonly dealt with by RIDOT. This manual is not to be used as a specification for RIDOT site investigations.