At the Amoco Company refinery in Yorktown, Virginia, potential sources and sinks of groundwater contamination were evaluated to determine the affects of the plant on the subsurface. Subsurface characterization of the refinery included an extensive subsurface sampling program that included 39 soil borings, 181 monitoring wells, and 23 surface water sampling points. Groundwater flow was modeled using FTWORK, a modification of MODFLOW. Results showed that, due to above ground process piping, contamination at the Yorktown refinery was significantly less than that observed at other refineries. Free-phase hydrocarbons were only detected in one monitoring well. Metals contamination was limited to monitoring wells associated with historic waste management activities at the east end of the refinery. Contamination was detected in monitoring wells located adjacent to process units but affects were limited due to the process sewer acting as a collection point.