Neptune Marina Ground Improvement Case Study

The waterfront Neptune Marina Development is located in Marina Del Rey Harbor, Los Angeles County, California. Four, 4-story wood-framed apartment buildings, covering a footprint of approximately 10 acres, are currently being constructed over a 2-level concrete subterranean podium parking structure, adjacent to the waterfront harbor. The current site soils are subject to liquefaction under the design earthquake. Should the site soils liquefy, there is the potential for structural damage due to foundation bearing failure and excessive settlement. In addition, the presence of continuous liquefiable soil layers poses lateral spreading hazard under a design earthquake event. The areas susceptible to lateral spreading are located toward the marina seawall. Working closely with the project team at the early conceptual stages of the project, Hayward Baker, Inc. (HBI), designed and built a comprehensive ground improvement program to mitigate the sites liquefaction and lateral spreading hazards, to provide adequate soil bearing capacity and settlement control under footings, as well as the temporary excavation supports. This paper will provide the detailed site investigation, liquefaction and lateral spreading analysis, the ground improvement design by vibro stone columns and soil mixing, the construction procedures, and QA/QC program with the lab and the field verifications tests.