A collaboration between Alameda County and the Judicial Council of California, the LEED Silver East County Hall of Justice (ECHOJ) consists of a five-story courthouse and a two-story county office building connected by a shared lobby and security screening area. The buildings serve the needs of eastern Alameda County residents. As part of the design-build team, Rockridge Geotechnical (RG) provided consulting services during design, construction observation, and testing services for the ECHOJ project. Using geotechnical boring and laboratory data collected by others, Rockridge Geotechnical prepared the geotechnical report, providing recommendations for the design and construction of foundations and retaining walls, earthwork, and remediation of the undocumented fill and surficial expansive soils present at the site. In addition, Rockridge Geotechnical performed a site-specific ground motion hazard analysis to estimate potential magnitudes of ground shaking at the site during future earthquakes. To develop site-specific response spectra for the project, RG performed probabilistic and deterministic seismic hazard analyses. During construction, Rockridge Geotechnical performed observations and testing of soil nail retaining walls, inspection of foundation excavations, and provided oversite during compaction testing, underground utility trench backfill, and grading of the building pads and pavement subgrades.