Rockridge Geotechnical (RG) performed the geotechnical investigation and developed recommendations for designing and constructing this six-story office building with two basement levels. Rockridge Geotechnical analyzed the historic groundwater levels and expected fluctuations because the basement levels extend below the historic high groundwater level. In addition, an existing culvert, adjacent structures, and surrounding streets required suitable shoring solutions to minimize the impact of construction. Deep soil mixing was selected to provide a hydraulic barrier to minimize groundwater inflow during construction. The excavation required tiebacks, as well as rakers where tiebacks were not feasible, due to adjacent improvements. The old Post Office façade was temporarily staged off-site during construction and supported with drilled piers. Rockridge Geotechnical performed a ground motion hazard analysis to develop a site-specific horizontal response spectrum for the Maximum Considered Earthquake and design levels of shaking.