Abstract: Three-Dimensional Geologic Modeling to Determine the Spatial Attributes of Hydrocarbon Contamination, Noval Facility Fuel Farm, El Centro, California

Chris Johnson, Stephen Mutch, Deems Padgett, Lauri Roche

An investigation was conducted at the Naval Air Facility located in El Centro (NAFEC), to determine the vertical and horizontal extent of hydrocarbon contamination at the facilities fuel farm. The fuel products are the result of tank and pipeline leakage, past tank cleaning, and past disposal of fuel dispensing and filter cleaning practices. Subsurface soil and groundwater data was collected via soil borings, monitoring wells, and CPT probes. Soil, groundwater, and analytical data were integrated using the LYNX geoscience modeling system (GMS). Interactive sessions with the data visualizer helped guide the modeling and identify data gaps. Modeling results indicate a continuous surface confining clay layer to a depth of about 12 to 15 ft. Groundwater is confined beneath this clay layer and monitoring wells indicate about 3 to 5 ft of artesian head. Hydrocarbon contamination is concentrated within this clay layer from about 5 to 12 ft below the ground surface. Residual fuel products located in the groundwater are attributed to slow leakage through the confining clay layer. LYNX was also used to compute volumes of contaminated soil to aid in remediation cost analyses. Preliminary figures indicate about 60,000 yards³ of contaminated soil. Since the contamination is primarily confined to relatively impermeable clayey soils, site remediation will likely be ex-situ land farming.

AAPG Search and Discovery Article #90981©1994 AAPG Pacific Section Meeting, Ventura, California, April 27-29, 1994