From Industrial to Educational
An urban school district planned to acquire a city site of about three acres to construct a new school: they engaged Isett to conduct both a Phase One and geotechnical investigation of the site. Previously a lumber yard, the site had been used for commercial/industrial purposes. Historical investigation revealed that the site once contained a rail yard and about half-a-dozen buildings that had been demolished over the years. Two other buildings remained standing.
Subsurface investigation revealed industrial fill at locations throughout the site, with overlying pinnacled limestone. During the initial planning, the design team anticipated using cast-in-place deep foundation columns to support the building. In order to confirm the applicability of the proposed deep foundation system, bedrock probing was conducted at the proposed column locations. Our investigation revealed that rock ledges at the proposed site were not sufficient to bear the column loads.
Isett worked with the architect, client and construction manager to develop a more applicable deep foundation system based on the additional subsurface information. When the initial bid for micropile construction came in at 1.2 million dollars, Isett assisted the district in locating equally-qualified contractors able to do the work for $750,000—a savings of more than $350,000!
Our geotechnical report provided recommendations on construction considerations concerning limestone/karst subsurface conditions, site preparation/demolition practices, design parameters for subgrade walls and foundations, concrete slabs, sidewalks and pavements, seismic design, excavation, groundwater control, structural fill and compaction.