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are included in Appendix D, Geologic Cross Sections. The geologic cross sections trends north-south and east-west across the site. Groundwater has been noted at depths ranging from 34 to 36 feet bsg in ,dune 1990, from 38 to 40 feet bsg in May 1991, and 41 to 43 feet bsg in December 1992. First encountered groundwater appears to be unconfined and exists within a clayey silt and silty sand zone. The zone extends from approximately 35 to 50 feet bgs. 2.2 Chemical Distribution in Soil Data on the distribution of chemicals in the soil beneath the site are based on analytical data for samples collected from 16 soil borings (Appendix A). Soil appears to contain gasoline hydrocarbons beneath and adjacent to the eastern dispensers. The approximate lateral extent of gasoline hydrocarbons is roughly circular, approximately 84 feet in diameter Figure 4 depicts the approximate lateral extent of residual gasoline hydrocarbons in soil. The vertical extent of gasoline hydrocarbons is from approximately 15 to 35 feet bsg. The approximate volume of soil containing gasoline hydrocarbons is approximately 4,000 cubic yards The calculated mass of gasoline within this impacted area is approximately 5,600 pounds of gasoline or 896 gallons. 2.3 Chemical Distribution In Groundwater �• Petroleum hydrocarbon compounds have been detected in all the eleven groundwater monitoring wells installed on- and off-site. This data indicates that off-site sources may be contributing to the groundwater impact in the site area. Access to adjacent properties for further definition of groundwater impact is being pursued. Due to the uncertainty related to multiple source areas around the site, groundwater remedial actions are not considered appropriate. The groundwater analytical data collected from the 11 wells through December 1992 is included in Appendix B. 3.4 INTERIM REMEDIATION SYSTEM DESIGN Interim remedial actions are proposed to address soil containing gasoline hydrocarbons which remains in the subsurface centered around the eastern pump island Soil vapor extraction is the selected remedial option for source removal The following sections detail an interim remediation system design for soil vapor extraction at this site. 3.1 Site Health and Safety Plan Prior to commencing the interim remediation phase of the project, the existing Site Health and Safety Plan (SHSP) will be revised to reflect the additional activities to be conducted on-site. The revisions will be prepared in accordance with Occupational Safety and Health Administration (OSHA) guidelines set forth in"Hazardous Waste Operations and Emergency Response" (29 CFR 1910 120). The SHSP will be reviewed and signed by all SEACOR TEXSTOCK SRW SERCOR N0001-006-01 3