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B contains analytical reports from the most recent sampling event The locations of the wells are presented on Figure 2 Based on the results of the most recent sampling event, it does not appear as though the concentrations and distribution of the various hydrocarbon constituents have changed significantly since the previous sampling event The plume of impacted groundwater still appears to remain in the immediate vicinity of the former tanks and does not appear to have impacted offsite properties While trace toluene concentrations appeared in W-6 during the December 1993 groundwater sampling event, no hydrocarbons were indicated during the July sampling event Depth to groundwater has decreased across the site by approximately one foot since the previous sampling event, and groundwater flow changed from east in December 1993 to northeast in July 1994 This change may be due to natural seasonal variations or local agricultural irrigation, however, not enough data has been collected to determine the cause of these changes Summary of Findings Pertinent to Selection of Remediation S stem Based on the findings of environmental investigations and groundwater monitoring events conducted at the subject site between April 1992 and July 1994, it appears that the extent of hydrocarbon-impacted soil is well defined and remains limited to the area of the pump islands and north portion of the former tank bed Groundwater beneath the site does not appear to have been significantly impacted by hydrocarbons Soils at the site generally consist of fine to medium sands to a depth of approximately 15 feet This strata is underlain by a clay unit which is approximately 5 feet thick Fine to medium sand is present from a depth of 20 feet to the extent of each boring During the initial investigation (Canonte, April 1992) , groundwater with an east-southeasterly flow direction was encountered at a depth of approximately 16 feet below ground surface However, in the December 1993 sampling event an easterly flow was noted, while during the July sampling event a northeasterly flow was noted To evaluate remedial options, a vapor extraction pilot test was conducted at the subject site in December 1992 Results indicated that vapor extraction would be a feasible remedial alternative for remediating impacted soils beneath the site For your convenience, a summary of previous site activities conducted from April 1992 through August 1994 is included as Attachment 1 Com arison of Remedial Alternatives SEACOR's "Problem Assessment Report" dated May 31, 1994, contained an evaluation of several remedial technologies for cleanup of impacted soils in the vicinity of the former tank system soil excavation and disposal, soil excavation and on- site aeration, soil excavation and off-site aeration, and in-situ soil vapor extraction Based on the excellent results achieved during the vapor extraction pilot test . and the low cost of installing and operating such a system, other remedial methods involving excavation were not considered feasible for soil cleanup