In Stockton, we often see pavement failures that trace back to the expansive clay subgrades common across the Central Valley. The San Joaquin River Delta creates a unique moisture regime where the water table sits within a few feet of the surface in many areas, and seasonal drying cycles cause significant volume changes. A pavement section that works in Manteca will not necessarily hold up on the north side of Stockton without adjusting the structural number. We design flexible pavement systems that account for these local conditions from the subgrade up, using site-specific resilient modulus values rather than generic assumptions. Before finalizing the asphalt layer thicknesses, we typically run a CBR field test to calibrate our inputs and confirm the subgrade strength under actual moisture conditions.
A flexible pavement in Stockton fails from the bottom up. Without controlling the subgrade moisture, even a well-designed asphalt layer will rut within the first five years.
