Oakley Prewett Ranch Elementary School,
Antioch Unified School District, California
Earth Systems company’s personnel prepared a geologic hazard evaluation and soil engineering study for the development, which included foundation design criteria, and recommendations for site preparation and grading. Part of the Antioch Unified School District, the new school comprises 13 one-story modular buildings, and associated playfields and paved areas.
The primary geotechnical hazards at the site were low density dune sands and the potential for liquefaction and sand boils. Mitigation measures consisted of over-excavating the building pads approximately 8 feet and reconstructing the building pads with recompacted soil to create a uniform soil mat under each building to eliminate the seismically-induced dry sand consolidation of the near-surface sandy soils. Two layers of geotextile fabric were installed near the bottom of the subexcavation to mitigate sand boils under the building.
Earth Systems' certified technicians provided testing and observation services during the grading operations. | 
