A stretch of Chapman Avenue in Orange, California, recently required a full pavement rehabilitation after years of heavy bus traffic had cracked the asphalt. The city's alluvial soils, deposited by the Santa Ana River, vary dramatically within a single block. We were called in to characterize the subgrade before any overlay design could proceed. That meant drilling test pits, running CBR tests, and classifying soils under the AASHTO M 145 system. The subgrade evaluation directly informed the required base thickness. Without that data, the new pavement would have failed within two seasons. Road geotechnics in Orange California demands site-specific investigation because the soil profile shifts from sandy loam to clay-rich layers within meters.
The alluvial soils of Orange require site-specific CBR values because a 10-foot shift in test location can change the bearing ratio by 30 percent.
