The foundation failure of the 22 story, steel framed, federal courthouse in Philadelphia occurred because of an inadequate geotechnical assessment of a complex geological condition. The founding elevations for caissons were improperly determined on materials that could not sustain the design load. This condition was further complicated by the presence of groundwater and poor concrete construction practices. These conditions resulted in an extensive and costly remedial measures which included a grouting program and the replacement of 14 faulty caissons
