Cameron-Cole constructed a multilayer numerical groundwater flow and solute transport model to evaluate the extent of impacts that historic operations at a major oil refinery and its associated pipelines have had on the groundwater and quality of an adjacent municipality in confidential location. The model was constructed using MODFLOW, Modpath, and MT3D to characterize the regional groundwater flow and fate and transport of benzene downgradient of the area of the refinery and determine the hydraulic effects of large-scale pumping (3,000-4,000 gallons per minute) at the refinery for process water. Based on the detailed hydrogeologic and contaminant transport analysis, Cameron-Cole concluded that the pumping from the refinery’s 16 on-site water production wells dramatically altered the natural (non-pumping) groundwater flow regime in the area to the west of the refinery. The alteration of the groundwater table in the aquifer beneath the refinery led to the advective transport and hydrodynamic (mechanical) dispersion of dissolved benzene beneath more than 200 residential properties and the municipality bordering the refinery. In addition, the alteration of the groundwater flow pattern and accelerated movement and dispersion of the hydrocarbon plume resulted in increased benzene vapor migration from the groundwater table into residences near the refinery, increasing health risk. The results from Cameron-Cole’s groundwater computer modeling simulations using the calibrated MT3D transport model in conjunction with MODFLOW (the flow model) indicated that benzene at concentrations at or above regulatory standards extended in a 1,000-foot-wide band extending off-site downgradient from the refinery’s fence line. Groundwater analytical data maps, hydrogeologic cross-sections, isoconcentration maps, and groundwater flow and transport modeling work completed by Cameron-Cole demonstrated that benzene releases originating at the refinery during its time of operation from approximately early 20th to early 21st centuries migrated west across a nearby highway and continued to cause risks to downgradient receptors. The numerical and hydrogeologic analysis demonstrated that increased mechanical dispersion, aquifer mixing, and hydrocarbon dissolution around pumping centers is an inherent drawback of groundwater pumping, as the spreading of dissolved contaminants due to the increased groundwater flow velocity is unavoidable. The groundwater flow and transport modeling work completed by Cameron-Cole was used to demonstrate that releases originating at the refinery during its time of operation from early 20th to early 21st centuries have adversely impacted more than 200 homes living near the refinery and the municipality itself. The refinery’s groundwater production wells were shown to have increased the dispersive spreading of benzene in the area west of the refinery, and these increases were demonstrated to be continuing well into the future. The computer modeling and hydrogeologic analysis were used as the basis for reaching a settlement in three separate civil action litigation cases regarding off-site trespass over several large neighborhoods adjacent to the refinery as well as the municipality.