AAA NEW HEADQUARTERS BUILDING
WILMINGTON, DELAWARE
------------------------------------------------------------------------------------------------------

Geotechnical
Duffield Associates was retained to provide a subsurface geotechnical evaluation for the AAA Headquarters Building, a proposed 6 story structure along the Christina Riverfront in Wilmington. Based on historic records and conditions encountered during the field investigation, the site was formerly utilized as a shipyard (circa 1870), with several timber ship launches located within the proposed building footprint and extending to the banks of the Christina River. In addition, the site was designated by the State of Delaware on the Hazardous Substance Cleanup Act (HSCA) listing, thus requiring specialized sampling and monitoring techniques during the geotechnical field evaluation. Further, the proposed building site was located partially within the active City of Wilmington Public Works yard, requiring careful coordination of field work activities.

During the geotechnical evaluation, test borings revealed highly variable site conditions including a layer of miscellaneous fill and historic urban debris overlying a relatively thick layer of compressible, organic soft consistency silt and clay soils. Beneath these soft soils, granular soils derived from the in-place weathering of parent bedrock were encountered to the extent of the test borings. After evaluating a number of foundation alternatives with the project team, Duffield Associates recommended a deep foundation system bearing in the dense granular soils at the site. An auger cast displacement pile system was selected as the most cost-effective approach for the building foundations.

Construction
Duffield Associates provided construction review services for all phases of site development. Services included review of deep foundation installation, site regrading, and reinforced concrete construction, as well as review of structural steel, and sprayed fire resistive materials. Duffield Associates provided engineering consultation with the project team and the City of Wilmington regarding static load testing of the piles, as required to meet local building codes.