The scope of this 1915 National Historic Landmark included installing pile caps, footings, columns, walls, new slab on grade and framed deck inside and beneath an existing seven-story building, working in and around mini piles supporting the structure. This scope included building two new structural levels beneath the existing building. Other additions: a seven-story concrete elevator shaft in the building core, requiring numerous infills and toppings to reconfigure existing floors; two large mechanical/utility vaults, retaining walls and footings. Unique features of this project include a raised acoustical slab and “super” lightweight concrete fill used to minimize the dead load of existing floors.