Ground penetrating radar (GPR) techniques were used with conventional lithostratigraphic information and water table elevations to develop a model for the hydrogeologic setting of a -0.5 km2 wetlands replacement site in southern Delaware, USA. The GPR profiles are a valuable component in the modeling because they provide a continuous, high-resolution image of the subsurface that cannot be provided by conventional coring and piezometric approaches. GPR data was gathered using a Sensors & Software, Inc. pulseEKKO IV unit using 50 and 100 MHz antennas. Over 2.3 km of common offset profiles were collected using the 100 MHz antennas with a transmitter-receiver separation of -1 m (3 ft) and a station spacing of -0.3 m (1 ft). 50 MHz data was also gathered to compare subsurface images using lower frequency antennas. Commonmid- point records were collected at -60 m (200 ft) intervals along the profiles. The quality of data collected with the GPR is excellent. The upper portions of the profiles contain a water table reflection (-1 m depth) that can be traced throughout the site.. Below the water table coherent reflections were obtained to depths greater than 10m. We have collected 7 vibra-cores to depths ranging from 2 m to 6 m along the profiles to correlate GPR reflections with changes in subsurface lithologies. Sediments encountered during vibra-coring consist primarily of fine to medium sands, silty clay sand, silty clay to clay, and a thin layer or quartz granules to pebbles. In addition to the vibra-cores conventional subsurface hydrogeologic information at the site includes sediment samples from borings, hand-auger cores, and water table elevations from piezometers.


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