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i <br /> I <br /> Ms. Linda Turkatte <br /> June 11, 1996 <br /> Page 7 <br /> SUMMARY <br /> The following summarizes the current known subsurface conditions for the Site and vicinity: <br /> • Soil and groundwater data collected during this investigation indicate a release of petroleum <br /> hydrocarbons occurred at the Site from the west end of the former UST complex prior to <br /> February 1994. <br /> • Soil beneath the Site can generally be divided into an upper silt and clay-dominated interval <br /> extending from the ground surface to approximately 38 to 44 feet bgs and an underlying <br /> sand-dominated interval extending to at least 54 feet bgs. The sand-dominated interval <br /> appears to represent the primary uppermost groundwater-bearing zone beneath the Site. <br /> Soil underlying the west end of the former Site USTs between depths of approximately 10 <br /> to 40 feet bgs is impacted with gasoline-range petroleum hydrocarbons. The lateral extent <br /> of petroleum hydrocarbon-affected soils within the vadose zone appears to be limited to a <br /> 20-foot radius from the approximate point of release. <br /> • In February 1996,groundwater beneath the Site and vicinity was interpreted to £low in an <br /> eastward direction;historically,the groundwater flow direction has ranged from northeast <br /> to southeast. , <br /> • Groundwater. directly beneath, and in the immediate vicinity of the former USTs, is <br /> impacted with gasoline-range petroleum hydrocarbons. Groundwater in the Site vicinity has <br /> been impacted by petroleum hydrocarbon releases from multiple UST properties and the <br /> Site is within an area of commingling plumes of petroleum hydrocarbons. <br /> RECOMMENDATIONS <br /> Based on the results of this Site investigation,SECOR on behalf of Metz, recommends the following: <br /> • Installation of two additional groundwater monitoring wells to further define the <br /> downgradient extent of petroleum hydrocarbons in groundwater related to former Site <br /> USTs. . <br /> • Initiation of quarterly groundwater monitoring activities for monitoring well MW-1 in <br /> coordination with consultants for the surrounding properties also impacted by petroleum <br /> hydrocarbons. <br /> • Performance of a soil vapor extraction/air injection pilot test to evaluate this technology as <br /> a possible remedial alternative for petroleum hydrocarbon-impacted soil and groundwater <br /> beneath the Site. <br /> HASUBORILLAPT <br /> 50090-011.02 <br />