As development continues, buildings and highways must be constructed over collapsible soils. Based on experience with behavior of loess in its natural state and after wetting, loess is classified as a difficult foundation soil, therefore improvement is typically recommended. Settlements associated with collapsible soils can lead to expensive repairs if not treated in some way prior to construction. Dynamic Compaction is a semi empirical technique for improving the mechanical properties of soil, developed by Louis Menard in 1970's. This technique was used recently in Romania for the treatment of 240,000m² of loess. This paper presents the criteria and tests used to certify the improvement of the physical and mechanical parameters of loess including its porosity, humidity, density, plasticity, additional settlement index, and structural resistance and deformation modulus.