The construction of a new LINAC vault adjacent to the existing hospital required an excavation 50 ft by 26 ft in plan and 33 ft deep.  The soil conditions consisted of loose sands and gravels to a depth of 8 to 18 ft overlying a shale and sandstone formation.

Due to a combination of access constraints, soil conditions, concerns about noise and overhead clearance constraints, Schnabel Foundation Company designed and constructed a hybrid shoring system that included hand-excavated piers down to a depth of about 14 ft.

Due to the presence of underground structures to a depth of 10 ft behind the shoring, the piers were internally braced.  Four rows of soil nailing were installed into the shale/sandstone formation below and in front of the piers.  This OSHPD-approved hybrid shoring system was a good example of the ingenuity our engineering and field staff bring to a project.