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EagleLift Installs (61) Helical Piles to a Stabilize School Building for Seismic Retrofit and for Expansion in Downtown San Francisco

EagleLIFT, Inc.

10410 Trademark St.

Rancho Cucamonga, CA, 91730


When the decision was made to upgrade and expand the old structure, the structural engineer determined that underpinning the entire building was required in order to provide the necessary structural support before excavating could begin.  Also, additional load bearing capacity was required to support the planned addition.

As with all new construction in San Francisco, seismic retrofitting is also a requirement.

Before excavation could begin, EagleLIFT crews installed (61) 1.75” RCS helical piles with 8”,10”12” bearing plates to depths ranging from 20 to 60 feet.  (55) of the helical piles were installed on the outside perimeter and (6) piles were installed on the interior.  The ultimate load requirement for the piles was 83 kips, and the working load was 55 kips.

The helical pile installation project was successfully completed in (20) working days.

An interesting bit of anecdotal information - the helical piles were all installed just a couple of days prior to the Napa seismic event. The structure was examined closely, and the engineer determined there was no sign of movement or a change of any kind.

Project Overview

The Gordon Lau Elementary School in downtown San Francisco was in need of considerable modernization including an addition.  Also, the structure needed seismic retrofitting.  EagleLIFT underpinned the existing foundation so the contractor could excavate around and beneath it and pour a new foundation.

Summer 2014