Evaluation of the Ground Penetrating Radar (GPR) Survey at TDCJ Playa, Carson County

A ground-penetrating radar (GPR) survey conducted at TDCJ playa, Carson County, imaged soil structures to depths of 2 to 4 m. Layering in soils, including the modern soils and several buried horizons, is parallel to the surface throughout the transect, which runs from the upland, down the slope of the playa lake basin, to the edge of the ephemeral playa lake. Little evidence of truncation of soil horizons is apparent on the images, suggesting that the playa basins are part of an accretionary rather than an incised landscape. Two trenches (1.9 to 2.5 m deep) and four boreholes near the GPR line confirm the horizontal structure of the soil and also document lateral changes not apparent on GPR. Interpretation of GPR is limited because of uncertainty in matching the GPR image to observed soil features, artificial changes in the character of the GPR image at segment boundaries, and sloping features on GPR images that could not be recognized in trenches.