Shallow High-Resolution Seismic Reflection Program To Characterize Hydrogeology

A shallow high-resolution (HR) seismic reflection program was conducted at the Department<br>of Energy’s Rocky Plats Plant near Denver, Colorado. The program was initiated to<br>characterize the hydrogeology of the site. The variability of the geology over relatively small<br>distances prompted the use of this method to enhance the borehole investigation program.<br>The HR seismic program consisted of three phases:<br>o seismic reflection modeling<br>o field tests consisting of approximately 375 records (1,500 feet)<br>o production phase consisting of 3,000 records (12,000 feet)<br>All data were collected using the common depth point (CDP) method. The seismic data were<br>processed using a rigorous set of algorithms. The results of each processing step were<br>carefully reviewed before proceeding to the next step. Interpretation of the seismic profiles<br>involved the integration of borehole lithologic and borehole geophysical data. Synthetic<br>seismograms were generated and seismic events were correlated to known, identifiable<br>geologic beds. The data from a vertical seismic profile were also used in the interpretation.<br>Seismic events corresponding to channel &posits were identified and mapped across a grid<br>The channel deposits consist of fluvial sandstones, siltstones, and claystones deposited in a<br>very low energy environment. These channel deposits provide a greater potential for the<br>migration of contaminants than the hosting claystone.