The biggest mistake we see on Stockton construction sites is relying solely on SPT data without verifying it against a continuous profile. The San Joaquin Delta's complex stratigraphy—organic peat lenses, soft clays, and loose silts layered within feet of each other—makes standard split-spoon sampling a gamble. Miss a thin, compressible layer at 18 feet, and you are looking at differential settlement that cracks slabs and misaligns equipment within the first two years. A Cone Penetration Test eliminates that blind spot, recording tip resistance, sleeve friction, and pore pressure every centimeter from the surface down to refusal. When we deploy the rig near the Port of Stockton or out toward Eight Mile Road, the continuous log picks up transitions that a 5-foot SPT interval simply cannot resolve. Combining CPT data with SPT drilling gives us both a high-resolution profile and physical samples for index testing, which is the standard of care for projects requiring Caltrans or City of Stockton Building Division review.
Continuous CPT logs catch the thin peat seams and loose silts that standard SPT intervals miss across the Stockton Delta.
