Seismic Reflection Survey For Mapping Groundwater Migration Pathways At Tinker Air Force Base, Oklahoma

Optimal placement of groundwater recovery wells in complex geologic environments often requires more subsurface<br>information than is available from boring log data, typically from widely spaced wells. A two-dimensional (2-D)<br>seismic reflection survey was conducted in the area of a planned groundwater recovery wellfield in the southwest<br>quadrant of Tinker Air Force Base (AFB) to help identify and map possible conduits for preferential groundwater flow<br>in the shallow subsurface. The primary targets of interest were near-surface sand channels and lenses within the upper<br>portion of the Permian-age Garber Formation, although the dataset also provided significant information on deeper<br>layers. The seismic data were acquired along eight survey lines totaling 17,510 linear feet.<br>The geophysical investigation at Tinker AFB included evaluating shear-wave (s-wave) and compressional wave (pwave)<br>seismic techniques along a short portion of one line to determine the best approach for the entire survey. Based<br>on the processed test sections, and consideration of s-wave data acquisition and processing costs, it was decided the pwave<br>survey offered an acceptable approach. The investigation also included acquisition of vertical seismic profile<br>(VSP) data, generating a synthetic seismogram from an existing sonic log, and collecting EM-3 1 data along each line to<br>assess the effect changes in near-surface soils, buried debris, and utilities had on the seismic data.<br>Seismic data were interpreted with the aid of PC-based software. To better understand the geometry and amplitudes of<br>some of the features observed in the site data, seismic models were generated with different combinations of velocity<br>and layer thickness. The interpreted seismic data indicate several locations where the potential for drilling into<br>significant sand lenses in the target zone is believed to be high. Deeper sand channel complexes cutting through the<br>target zone and extending to much greater depths are also interpreted. The results of Phase I groundwater recovery well<br>yield tests indicate good correlation with several of the seismic anomalies identified in the target zone.