THE OPPORTUNITY

PS&S was asked to provide full A/E services for design and construction of a six-story 717-space car precast parking garage. The garage is located adjacent to the Bergen County Courthouse and provides parking for the newly constructed Bergen County New Agency Building (Two Bergen County Plaza). PS&S provided architectural, structural, M/E/P and geotechnical design services. PS&S also provided structural and geotechnical design services for the New Agency Office Building. The garage includes a steel-framed roof encompassing the full footprint of the garage designed to support a mechanically fastened photovoltaic array.

THE CHALLENGE

The project site, located along South River Street, is within 400 feet of the Hackensack River, which resulted in challenging soil conditions typically requiring the use of pile foundations. The bearing stratum, located at an approximate depth of 200 feet below grade would require extremely long and expensive piles with multiple splices. An additional complication included upper level loose sands with a high groundwater table which was found to be susceptible to liquefaction under a seismic event.

THE PS&S SOLUTION

PS&S investigated alternative foundation systems that could eliminate the need for piles, address the potential for liquefaction, and provide adequate support for a heavy precast concrete building. Working with specialty contractors, PS&S determined the use of a stone column system would provide adequate bearing support for a shallow foundation system while also densifying the upper loose sand layer to resolve liquefaction concerns. The resulting foundation system consisted of shallow strip and spread footings closely resembling foundations built upon competent soils saving the cost of a deep pile foundation system.