GEOPHYSICAL INVESTIGATION OF THE BURD-RUN BURIED STREAM CHANNEL IN COLLUVIAL FILL OF THE CUMBERLAND VALLEY, PENNSYLVANIA

This study has focused on implementation of a multi-method geophysical approach using electrical resistivity, electromagnetic induction, and ground penetrating radar to investigate the dimensions, fill, and hydrologic parameters of a known buried stream channel along the Burn Run stream in Shippensburg, Pennsylvania. The buried stream channel was filled during stream restoration in 2001. Prior to infilling, the stream channel was mapped and characterized. Sandy silts mixed with a variety of organics, minor cobble materials from the restored stream channel, and topsoil was used to infill the channel and build it up to grade for development of recreational fields.

This study utilized a series of 4, 50-meter long transects oriented perpendicular to the long-axis of the ~10 meter-wide buried stream channel. Prior to geophysical investigation, the site was mapped using a total station to establish ground elevation differences and to establish trends in both surface topography as well as to identify potential subsurface groundwater flow pathways. Soil auger samples were taken for ground truthing of geophysical methods. Preliminary investigation using GPR (Mala X3M) and resistivity (OhmMapper) allow for delineation of different subsurface properties. The GPR (using both a 100 Mhz and 250 Mhz shielded antennas) yielded anomalies that could be clearly identified as the buried stream channel. At least three different fill packages were also identified and correlated to different fill components as detected in profile samples. Resistivity surveys show highly resistive signatures in the vicinity of the filled channel indicating that, although filled, the channel may still be transmitting groundwater.