Eugene’s growth from a muddy trading post along the Willamette River into a thriving city of over 175,000 has pushed development into areas with complex alluvial soils. The 1993 Scotts Mills earthquake, though centered north of here, rattled buildings in downtown Eugene and reminded everyone that the Cascadia Subduction Zone is not just a coastal concern. When you start a project on the valley floor, the loose silty sands and high groundwater table that characterize much of Eugene pose a genuine liquefaction threat. The International Building Code and ASCE 7 require a site-specific liquefaction analysis when these conditions are present, and our team has run these assessments from the Whiteaker neighborhood to the Gateway area. We combine field data with lab testing to determine if your site needs ground improvement or foundation adjustments before the first yard of concrete is poured.
A factor of safety below 1.0 means the soil loses strength during shaking – it is not an academic exercise, it is a construction deadline and a budget line item.
