Too many foundation bids in Irving still go forward with nothing more than a hand auger look at the top two feet. That gamble unravels fast when the boring hits a loose sand lens at 15 feet or a slickensided clay seam that swells 4 percent under load. We run the SPT hammer per ASTM D1586 because the Eagle Ford Shale and Trinity River terrace deposits that underlie the 75060 corridor and Las Colinas don’t read textbooks—they vary foot by foot. A 140‑pound safety hammer driving a split spoon every 2.5 feet gives us the N‑value profile that the structural engineer actually needs for bearing capacity, settlement estimates, and liquefaction screening under IBC Chapter 18. Where subsurface drainage is suspect, we pair the SPT log with an in‑situ permeability test to flag perched water before the excavator breaks ground.
Split‑spoon refusal at 50 blows says as much about the formation as 6 inches of sample recovery does—both numbers go straight into the bearing capacity calculation.
