A challenging Task: Excavation Support and Anchoring of the Foundation of San Francisco’s Trinity Place with DYWIDAG Anchors

In San Francisco, a new block of high-rise buildings are being constructed on an area of 130,715m² in the centrally located South of Market (SoMa) district. The development, named Trinity Place, is divided into four construction sections designed to relieve the city’s tight market for rental apartments by providing approx. 2,000 new units.

In section III, a 19 floor, L-shaped building is being built that will contain 546 apartments. Furthermore, a multi-level underground garage with a total of 940 spaces is under construction in sections III and IV.

The slab and piling foundation one level below grade for the tower that had been built during phase II had to be stable enough to construct the three adjoining basement levels for phase III.

The piling was used to prevent the settlement of the phase II building into the excavation for phase III. In order to efficiently stabilize the building and the excavation, 89 piles were sunk up to 10.7m (35ft) deep for the foundation. To tie back the soldier beam and lagging system, DSI supplied 623 temporary Type 0.6" DYWIDAG Strand Anchors with a total length of 12,404m (40,695ft). Since there are many utilities under the adjacent road, the shoring of the building was very complex: The tiebacks had to be installed from the utility space in the surrounding streets. DSI also supplied the equipment needed for testing some of the anchors.

To prevent uplift, 789 double corrosion protected (DCP) 57mm Ø, Grade 75 DYWIDAG Bar Anchors were installed and connected with the foundation using plate anchorages.

The limited space on site was a major challenge for all companies involved because there was no storage space on site. DSI reacted quickly to the customer’s continuously revised schedules and was able to supply the required products to the jobsite just in time.


Trinity Properties, USA

General Contractor

Swinerton Incorporated, USA


Malcolm Drilling Company, Inc., USA


Brierley Associates Corporation, USA


Arquitectonica International Corporation, USA

DSI Unit

DYWIDAG-Systems International USA, Inc., BU Geotechnics, USA

DSI Scope

Production, supply

DYWIDAG Products

623 temporary Type 0.6" DYWIDAG Strand Anchors; 789 double corrosion protected 57mm Ø, Grade 75 DYWIDAG Bar Anchors

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