A mixed-use building near the Whitaker neighborhood hit refusal at 15 feet. Cobbles and dense gravel over soft clay. That's Eugene. The upper layer tricks you into thinking you have bearing. Then the auger drops. We've seen this pattern from the Whiteaker to the Bethel area. The Willamette River and its tributaries left a complex stratigraphy. Shallow footings work in the south hills. They don't work on the valley floor. For those sites, pile foundation design becomes the only reliable path. We combine site-specific grain-size data with SPT refusal depths to pick the right pile type. Sometimes driven H-piles. Sometimes drilled shafts. The decision depends on what's below the cobble layer. That's what we determine before a single pile goes in.
In Eugene's floodplain, pile design isn't about bearing capacity. It's about surviving what the soil does during an earthquake.
