Alternative Foundation Design - Waterfront Redevelopment

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Project Description

Cost-effective redevelopment of a former lumber yard facility at the foot of the Fordham bridge on the Harlem River in the Bronx was jeopardized by a number of problematic geotechnical and environmental conditions. Whitestone reviewed soil boring data obtained through the City of New York and preliminarily evaluated information relevant to the proposed redevelopment for a self-storage facility. Based on the proposed loading and deep compressible fill material and organic deposits, a very costly deep pile foundation system appeared necessary.

Whitestone worked with the design team including the architect and structural engineer who reduced the building weight using light-weight materials and accepted modifications to the foundation design to produce a relatively light, uniform and distributed mat pressure. Even the moderate increase in soil loading from the lightened building would cause excessive settlement. In addition, materials were characterized as unsuitable bearing material per New York City building code.

Whitestone developed a unique solution consisting of removing a limited portion of soil equivalent to the proposed building weight and replacing it with high strength geofoam blocks capable of supporting the building weight. Because the weight of soil equivalent to the new proposed building weight was removed and replaced with the lightweight geofoam, the compressible soils experienced no increase in pressure, therefore limiting settlement to within tolerable limits. This option was presented and approved.

During the site design process, Whitestone also was engaged to design an on-site septic system that had been specified by a third-party civil engineer. Whitestone noted that Code requirements would preclude the placement of the septic per the initial concept, and subsequent testing in the proposed disposal field locations encountered soils that would not comply with New York City on-site septic system requirements. However, geotechnical and hydrogeolical analysis indicated that an on-site septic system would be feasible. Whitestone procured a meeting with NYCDEP’s Commissioner and presented its findings, resulting in approval for the on-site sewage disposal system. The design and construction included two phases of installation and testing in order to phase the work around existing buildings and demolition schedules. Both rounds passed tests as witnessed by New York City engineering representatives.

Whitestone also provided environmental consulting services during the project to identify areas of environmental concern and coordinate asbestos abatement activities.

Whitestone provided construction phase testing and inspection throughout the foundation and earthwork portions of the project including specifically reviewing grades, identifying safe areas to stockpile materials so as not to induce unintended settlement, placement and installation of geofoam blocks, and pouring of concrete frost walls and structural mat.