Schnabel designed and executed three types of underpinning systems (Type 1, Type 2, and Type 3) depending on building conditions.
Type 1: Used where trench walls were directly beneath footings, combining permeation grouting, hand-dug piers, and permanent tiebacks — forming permanent watertight trench walls.
Type 2: Micropile/pile cap underpinning (patent pending) for structures like the historic Amtrak building.
Type 3: Traditional micropile underpinning through column footings for larger structures, including the National Bowling Stadium.
In addition, Schnabel installed 202,800 square feet of temporary earth retention using soil nailing, soldier beams, and tiebacks to support roads, property, and the temporary railroad shoofly. These systems overcame challenging soils with cobbles, boulders, and high groundwater conditions