Soil Nailing Earth Retention on the Park Lafayette Development in Milwaukee, Wisconsin

The Park Lafayette development currently under construction in Milwaukee, Wisconsin consists of two 20-story towers supported on a combination of spread footings and drilled shafts. The development includes four levels of underground parking, requiring a 14m (45 ft) deep excavation immediately adjacent to city streets and Milwaukee County property. The presence of the adjacent County property required an unprecedented level of pre-construction planning by the Developer, Construction Manager Hunzinger Construction Company, and Specialty Contractor Edward E. Gillen Company. The small site footprint required that the earth retention system be installed such that the retention system would also serve as the backside form for the foundation walls. The 13 corners in the foundation footprint complicated this necessity. Gillen and Hunzinger determined that soil nailing would be the most cost effective method to retain the excavation. To avoid conflicts with new foundation walls, the excavation footprint was oversized 150 mm (6 inches) on each side to allow for irregularities in the excavation and shotcrete face and lateral movement of the earth retention system. Construction of the soil nail wall proceeded through the winter of 2006 to 2007 with minimal delay. Optical survey monitoring by the construction manager indicated that the 150 mm (6-inch) wall offset was sufficient to allow foundation wall construction to proceed with modifications to neither the retention system nor the foundation walls.