Block 9

Mastering SOE and CSM Techniques on San Francisco’s Block 9 Project

Cutter soil mixing, tie-backs, internal bracing, and jet grouting columns were employed in the multi-residential project on Block 9 in San Francisco. The project consists of a 43-story tower and two smaller towers on either side. While constructed as a single building, it will give the impression of a high-rise building flanked by two low-rise structures. The development includes 570 residential units, shared open spaces, amenities, and retail along Folsom Street. An underground garage provides parking for both cars and bicycles, accommodating all units.

For Malcolm, this project presented an opportunity to implement a well-planned and executed approach to support of excavation (SOE) on an exceptionally challenging site. At 6 stories deep, it marked the deepest planned excavation in the Transbay District at the time. The project addressed challenging soil, bedrock, and groundwater conditions, known deep obstructions, and provided tight deformation control for sensitive adjacent residential and freeway structures. The excavation was supported by a combination of cutter soil mix (CSM) walls, tie-backs, internal bracing, and jet grouting columns at the base to address liquefaction concerns.

Malcolm Drilling