Ground Improvement is Rarely a One-Sized Fits All Solution: a Case Study on Ground Improvement at a Pennsylvania Distribution Center Site

Throughout the world, there are typical site issues/constraints that could be considered a regional issue, such as soft, silty soils in alluvially defined areas or organic soils found in former marshlands. In areas of variable topography, earthwork, retaining structures, and slope stability are paramount challenges. A case in point is the uncontrolled strip-mine turnover found in the coalfields of northeastern Pennsylvania where the propensity is for available sites to share critical problematic characteristics – massive grading challenges and the presence of uncontrolled mine fills from historic mining operations. At the site of a speculative warehouse distribution center in Olyphant, Pennsylvania, both of these typical issues were present, the latter of which was exacerbated by the higher-than-average fines content of the fill materials, making them more susceptible to changes in moisture content. To further complicate matters, the onset of site construction was set for late fall of 2021, following excessive levels of rainfall in the northeastern United States over the previous two to three months, which led to significant quantities of trapped water within the mine spoil material. This paper will provide a case study on the efforts undertaken to identify and address the issues outlined above, focusing on the several geotechnical construction techniques required in concert to stabilize the site. Specific discussion will focus on the dynamic compaction program implemented for fill stabilization throughout much of the site, the aggregate pier program that became part of the solution in sufficiently loose and saturated areas, and the implementation of a settlement monitoring program conducted following the placement of up to 29 ft (8.8 m) of structural fill to establish the proposed site grades following the ground improvement work.