The eastern Los Angeles Basin floor beneath Pomona is a complex sequence of Quaternary alluvium—sands, silts, and gravels washed down from the San Gabriel Mountains. At roughly 850 feet elevation, the city sits on soils that can vary from dense coarse deposits to pockets of finer sediment just a few blocks apart. We see this daily in the lab: split-spoon samples from one site show clean gravel with high blow counts, while the next block over reveals silty sand that demands a completely different bearing capacity approach. For shallow foundation design in this setting, the difference between a straightforward spread footing and a problematic one often comes down to how well the site investigation captures that variability. Our team runs the full sequence—from SPT drilling to index testing—so the foundation recommendation matches what’s actually underground, not a regional assumption.
In Pomona’s alluvial soils, bearing capacity can shift from 3,000 psf to over 8,000 psf within a single block—site-specific testing is the only way to design footings you can stand behind.
