King of Prussia Mall Expansion

The premier shopping destination of the Philadelphia suburbs, the King of Prussia Mall formerly consisted of two buildings known as The Plaza and The Court. Owner Simon Properties embarked on a connector project that involved a 150,000+ sf expansion of the mall and a new parking garage. Schnabel was brought in to peer review bid documents and was subsequently engaged to value engineer and redesign the foundations.

The project site was underlain by an active karstic rock unit (Ledger Formation) with pinnacled bedrock, open and soil-filled voids, and known sinkholes. After providing a peer review of existing micropile foundation bid documents, we were retained to value engineer and redesign the micropile foundations for the new connector and parking garage. Through a higher level of analysis and design efficiency, we were able to provide a micropile foundation that enhanced the effectiveness of the micropiles by eliminating unnecessary conservatism, reduced pile cap sizes, minimized the potential for pile installation conflicts, and controlled grout quantities.

We worked closely with the structural engineers and construction management teams from design through construction, including the treatment of anomalies often encountered in karst foundations. Our redesign reduced the number of micropiles needed by about 30%, resulting in a cost savings of more than $1 million in pile construction costs. The owner realized additional savings in pile cap materials, labor, and – perhaps most importantly – schedule.