The Fourth Street Overcrossing and Highway 101 project involved the reconstruction of the existing two-lane overcrossing structure and interchange configuration. The replacement structure is seven-lane and approximately 97 feet wide. Geotechnical services focused on the removal and replacement of the existing structure, the construction of a southbound auxiliary lane, and the removal and realignment of on- and off-ramps. Earth Systems performed a soils engineering investigation and during construction provided special inspection of construction materials and observation and testing of the grading operations.