The pressiometer test developed by MENARD in the 50s has greatly contributed to the development of semi-empirical calculation methods allowing fairly simple access to soil behaviour laws (stress – deformation) directly exploitable in the dimensioning of civil engineering structures. However, the interpretation of this test seems to be still perfectible, in the light of the differences in behaviour observed between the theoretical and actual expansion mechanisms of the pressiometer probe [1][2]. These discrepancies seem to lead to an overestimation of the pressiometer characteristics of the terrain, especially when using a thick membrane probe or a split tube. This state of affairs leads us to question ourselves as project manager / project owner on the impact of these discrepancies on the dimensioning of our structures. In a tense economic context and where the search for the limitation of the human footprint on the environment becomes essential, it is our responsibility to evaluate as accurately as possible the real physical behaviour of the soil, while of course maintaining the safety coefficients inherent in the uncertainties of the dimensioning of a structure, and this in order to evaluate as accurately as possible the cost of our projects (financial and environmental). This paper resumes the five improvements of the new interpretation : taking into account the thickness of the membrane; taking account of the real deformation of the probe; determination of the precision of the main results; determination of the elastic modulus and the friction angle of the soil. In the case of a dam on Rhone river, it infers different soil characteristics than the standard interpretation, and allowed different retaining wall technology. The financial impact of the better knowledge of the site is estimated in terms of economy but also security