Letterkenney Army Depot Site Investigation

Princeton Hydro was contracted by the United States Army Corps of Engineers (USACE) Philadelphia District to perform a geotechnical evaluation in support of the proposed site improvements at the Letterkenny Army Depot in Chambersburg, Pennsylvania. The base focuses on the maintenance, modification, storage, and demilitarization of equipment for the United States Army. The base consists of numerous buildings/warehouses and parking/storage lots for military equipment spanning over 18,000 acres.

The area in which the site work was conducted is approximately 10 acres in size and is the proposed area for a new consolidated Shipping and Receiving Warehouse for receipt of items and component materials being inducted into the depot for recapitalization or reset.

For this field investigation project, Princeton Hydro was tasked with coordination and oversight of a Geophysical survey of the project area to identify, delineate, and characterize subsurface targets; performance of fourteen (14) geotechnical borings with associated rock coring to supplement USACE design of the site improvements; and performance of three (3) test pits to determine the depth to groundwater/seasonal high groundwater as well as the rippability of the bedrock on site.

For the geophysical survey, Princeton Hydro subcontracted Hager-Richter Geoscience. This survey included ground penetrating radar (GPR), time domain electromagnetic induction metal detection (EM61), and precision utility location. During the geophysical survey, Princeton Hydro was on site to act as a point of contact with the client as well as the Site Safety and Health Officer as outlined in USACE EM 385-1-1.

For the geotechnical borings and test pits, Princeton Hydro subcontracted CGC Geoservices. Borings were completed by way of a CME-55 truck mounted drill rig. In each boring advanced, sampling was performed continuously until the target depth was achieved. If bedrock was encountered before each target depth, rock coring was performed until a minimum of 10 feet of recovered core sample was observed to be competent rock. Test pits were completed by way of a John Deere 310L EP rubber tire backhoe. Test pits were advanced to bedrock, at which time the backhoe would attempt to progress until bucket refusal to determine the rippability of the rock. Princeton Hydro was on site during all geotechnical borings and test pits to prepare descriptive boing/test pit logs as well as act as the Site Safety and Health Officer as outlined in USACE EM 385-1-1.

Upon completion of the field investigation, Princeton Hydro performed laboratory testing on select soil sampling representative of the stratigraphy observed at the site in our in-house AASHTO accredited and USACE validated materials testing laboratory. The results of the lab testing were utilized to establish subsurface strata to aid USACE with the design of the proposed site features.