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1 <br /> 1 <br /> ' 4 0 CONCLUSIONS AND RECOMMENDATIONS <br /> Results of the preliminary investigation and evaluation indicate that soil and groundwater have <br /> been impacted by elevated concentrations of gasoline hydrocarbons, including BTEX, MTBE, and <br /> other oxygenate compounds <br /> Given the high percentage of porous sandy soil beneath the site, and the successful removal of <br /> ' impacted soil during the canopy support over-excavation, the remaining mass of petroleum <br /> hydrocarbons in soil does not appear to be large The lateral and vertical extent of soil impacted <br /> by TPH-as-gasoline and BTEX compounds is mostly defined to an interval approximately five feet <br /> ' thick and approximately 2,500 square feet in area, under the southeast corner of the dispensers <br /> Gasoline hydrocarbons released from the former fueling system appear to have leached to <br /> groundwater and migrated on the groundwater surface to the north and northeast of the fueling <br /> system The lateral extent of impacted groundwater is undefined to the west, north and east of <br /> the site MTBE also appears to have migrated vertically in soil beneath the water table and first <br /> saturated soil interval <br /> Given that the nearest municipal water well is cased to a depth of 130 feet and it is approximately <br /> 1,500 feet southwest of the site, and given that the plume of impacted groundwater appears to be <br /> mostly defined to the southwest, it is unlikely that any municipal water wells have been impacted <br /> by the release of gasoline hydrocarbons at the subject site However, several shallow domestic <br /> wells are located east of the site, on the residential parcels along Raylow Avenue and Mylnar <br /> Avenue <br /> ' Based on the results of this investigation, Ramage Environmental recommends that a work plan <br /> be prepared which outlines the following course of corrective action <br /> 1 1 Install three on-site groundwater monitoring wells to confirm the presence and concentration <br /> of gasoline hydrocarbons in groundwater beneath the site, to evaluate groundwater flow and <br /> ' gradient characteristics, and to establish a groundwater monitoring capability at the site Once <br /> the three wells have been installed and sampled and the direction and gradient of <br /> groundwater flow has been determined, additional wells may be required to define the extent <br /> of impacted groundwater <br /> 2 Evaluate the vertical extent of impacted sod and groundwater beneath the site A cone <br /> ' penetrometer testing (CPT) rig could be used to identify deeper groundwater-bearing intervals, <br /> and a SimulProbeo tool could be deployed to collect discrete sod and groundwater samples <br /> 15 <br />