ASCE Orange County Geo-Institute Event – Landmark 2 tower: New high-rise in Existing Basement, near Santa Monica Fault

Presentation Abstract The Landmark Apartment building is a new 34-story residential tower constructed in West Los Angeles within the footprint of an existing four-level subterranean parking structure that also supports an adjacent, fully occupied 17-story office tower. The geotechnical conditions were unusually constrained: heavy new column loads adjacent to 1980s-era spread footings that could not tolerate differential settlement, a permanently dewatered basement with groundwater at the original gravel subdrain layer, and demolition of a tower-footprint "glory-hole" that removed the diaphragms providing lateral restraint to the perimeter basement walls. The new tower is supported on 4-foot-diameter CIDH drilled shafts, 65 to 90 feet long, installed with drilling mud through saturated alluvium and taking advantage of a coarse-grained stratum at depth. Replacement wall restraint combined tiebacks with internal rakers on micropile foundations. This presentation walks through the foundation selection, drilled shaft design, shoring system selection and design, dewatering strategy, and the construction sequencing…