**1. Introduction**

The building for dam required a need for better understanding geological and mechanical properties of investigated sites. This process leads to a comprehensive site characterization and contributes bringing additional work when construction and dam foundation materials need some requirements in order to improve it. These additional works lead maintaining dam stable during his service life. Rock physical and mechanical properties are very important parameters for geological engineering design and construction of dams. Given the number of factors in the designing and construction of dams it can be referred primarily to locally available materials and dam foundation conditions whether these factors fulfilled both geological and geotechnical conditions. Thus evaluation of construction materials and dam foundation must be performed to ensure that these factors are satisfied. Geophysical techniques such as seismic velocity are used to derive quantitative engineering design values in order to assess geotechnical and geological properties during dam site investigations [1–4]. In this chapter, field investigations, borehole logging techniques and seismic velocity measurements are given in order to assess the geological and geotechnical of the Ntem formation and soil deposits that have been used both as construction and foundation materials during dam construction. Both refer to previously published work on Ntem formation characteristics [4] and unpublished data of soil deposit natures in the dam site at Memve'ele.
