Karst Area Geotechnical Investigation & Subsurface Improvement

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Project Description

Allentown Crossings is a light industrial development that serves several major metropolitan markets accessed through Philadelphia, Harrisburg, the Port of Newark and the Port of Baltimore. Whitestone’s client developed large warehouse facilities in the tract, including the 290,000 square foot DHL package sorting and distribution facility shown above. As part of the overall tract development, Whitestone provided a full range of geotechnical and environmental services from due diligence evaluations prior to property purchase through design-phase subsurface investigations, environmental site characterization, geological hazard mapping, and construction phase consultation.

Under accelerated schedules during property due diligence review periods, Whitestone evaluated subsurface information relevant to potential cost and impactive conditions, and conducted preliminary geotechnical investigations designed to assess geotechnical issues including soil re-use options, depth to groundwater, karst characteristics, and impacts of potential problematic subsurface conditions. Whitestone’s preliminary investigations were performed in accordance with Township subdivision and land development ordinances. Maps of geologic hazards associated with the sinkhole prone geology were created. Whitestone’s environmental due diligence services included reviewing publicly-available records to determine if past or current environmental enforcement, investigative or corrective actions had been implemented at or in the vicinity of the properties or if culturally or historically sensitive areas had been documented on the sites as well as an assessment of potential recognized environmental conditions.

By identifying site constraints prior to acquisition, Whitestone tailored design phase investigations toward potential adverse development issues such as karst features (sinkholes, lineaments, and closed depressions) and a former mining area that was identified on one parcel. Whitestone delineated the former mining area and determined that it was located beneath proposed structures and access roadways. Whitestone’s initial findings led to revising site plan concepts to minimize impacts due to poor subsurface conditions associated with uncontrolled mine spoils fill, moisture sensitive soils, and karst conditions. Whitestone developed cost-effective recommendations including:

  • minimization of soil overexcavation and off-site disposal by mechanical subgrade improvement with a bi-axial geogrid,
  • mitigation of earthwork delays with moisture sensitive soils through chemical stabilization, and
  • repair of existing sinkholes.

Whitestone was an active part of the structural design team, and provided specific analyses for very heavily to very lightly structural loaded areas to value engineer foundation design.

During construction phases, Whitestone attended pre-bid conferences and coordinated value engineering measures based on specific means and methods of various site contractors, such as modifying asphalt lift thickness to expedite pavement operations.