The renovation of this existing regional mall included a 275,000 sf vertical expansion over six existing one-story buildings, addition of new tenant buildings and construction of five new parking structures. Plans for the vertical expansion required an innovative solution to minimize impact on existing ground level tenants who remained fully operational throughout construction. Major roof trusses spanning up to 135 feet were used to suspend the new second floor from the new roof structure, minimizing construction within tenant spaces. Due to the project’s location within the floodplain of the San Diego River Valley, the potential for seismically induced liquefaction of the supporting soils was considered to represent a significant hazard. A careful analysis of foundation options were conducted, including the potential for settlement induced structural damage, settlement of existing foundations induced by new foundation construction, potential tenant disruption of spread footing versus driven pile construction. Overall construction costs were balanced against potential risks.