In Santa Ana, the near-surface soils often mislead builders. A dry summer crust hides fat clays underneath. We see this pattern across the city, from the Civic Center area to the industrial lots near South Coast Metro. The issue is moisture. When it rains, those clays swell. When it’s dry, they shrink. That movement cracks slabs and shifts shallow footings. Atterberg limits testing cuts through the guesswork. It gives us the liquid limit, plastic limit, and plasticity index. With those three numbers, we classify the soil per ASTM D4318 and the Unified Soil Classification System. No surprises later. Just data. For deeper bearing layers, we pair this with SPT drilling to confirm stratigraphy before the structural design locks in.
A plasticity index above 25 in Santa Ana means one thing: the clay will move. Plan for it.
