The seismic refraction tomography (SRT) method, which is environmentally compatible was used to evaluate the in situ geotechnical properties of rocks in El Alamein, a new city of northwestern Egypt. SRT data were obtained along nine profiles. The results of primary wave velocities (Vp), which are 400 to 1000 m/sec for the first layer, 700 to 1250 m/sec for the second layer, and 550 to 1150 m/sec for the third layer, and secondary wave velocities (Vs), which are 150 to 330 m/sec for the first layer, 230 to 430 m/sec for the second layer, and 170 to 390 m/sec for the third layer, were correlated with the data extracted from nine boreholes drilled within the study area. The elastic moduli (kinetic rigidity, modulus, young modulus, and bulk modulus) and the geotechnical characteristics like Poisson's ratio, stress ratio index, concentration index, material index, N value, density gradient, and bearing capacity of the foundation materials were calculated from the propagation velocities of the different types of seismic waves. These elements were combined to determine the most suitable site for construction. The area can be categorized based on cohesive layer thickness, soil cohesion from geotechnical properties, and proximity to test wells into two zones: (1) unfit for construction due to weak soil cohesion caused by seawater intrusion and thin buildable layers, (2) suitable for construction at one or two levels, with strong soil cohesion, thicker buildable layers, and less noticeable seawater interference.