This paper presents a case history of Lean Concrete Column (LCC) design, prediction, installation, and monitoring for a 34-story high-rise condominium tower over a five-level underground parking substructure supported on a mat foundation in San Diego, California. The site constraints and the building configuration imposed unusual design and construction challenges, which resulted in high foundation pressures and eccentric loading for the planned building mat foundation. A geotechnical investigation consisting of deep test borings, Cone Penetrometer Tests (CPT), and laboratory tests indicated that formational soils underlying the site did not provide the necessary bearing capacity to directly support the structure on a conventional mat foundation system within acceptable settlement and structural limitations. Design constraints, economics, and constructability issues dictated solutions requiring an integral waterproofed substructural system supported on a mat foundation. A foundation system incorporating conventional piles structurally tied into the mat was not feasible because of waterproofing constraints. A determined practical solution was to incorporate a ground improvement technique that would be separate from the mat foundation, provide improved mat support, and reduce differential settlement to within tolerable limits. LCCs were found to be a viable method of ground improvement for reducing differential settlement of the mat to acceptable limits
