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Laboratory analysis determined that no TPHg or BTEX constituents were detected in any of the monitoring wells Well MW2 and MW3 was reported to contained TPHd at low concentrations of 60 and 72 parts per billion (ppb), respectively Analytical results are summarized in Table 2 Copies of field notes and well purge logs are included in Appendix A and copies of laboratory reports and chain-of-custody documentation are included in Appendix B 2.22 Vapor Extraction System Monitoring and Analyses ' During Fourth Quarter 1995, a representative from Smith Environmental was on site weekly to record the flowrate, concentrations, temperature, and vacuum of the soil vapor extraction system and perforin routine maintenance Copies of field notes are included in Appendix A On October 26, November 20, and December 26, 1995 vapor samples were collected from the P influent sampling port for hydrocarbon analyses The vapor samples were analyzed for TPHg using Environmental Protection Agency (EPA) Method 8015M and BTEX using EPA Method 8020 by Sequoia Analytical in Redwood City, California Air sample results are summarized in Table 3 and laboratory reports and chain of custody documentation is contained in Appendix C 3.0 HYDROGEOLOGIC SETTING The subject site is located at 1702 Jackson Street in Escalon California (Figure 1) The site is situated at an approximate elevation of 119 mean feet above sea level, in the San Joaquin Valley geologic province Local surface sediments consist generally of well graded sand and poorly graded sand During the period of investigation, the depth to groundwater at the site has ranged from 67 23 r feet (MW-4, March 29, 1994) to 70 14 feet (MW-1, September 15, 1995) below grade When groundwater levels were last measured on January 9, 1996, the depth to water ranged from 67 79 ' feet (1,, W-4) to 68 28 feet (MW-2) below grade The direction of groundwater flow has been generally west to southwest, with a gradient magnitude of approximately 0 002 feet per feet 4.0 SITE BACKGROUND The site is located in a commercial and residential area in Escalon, California (Figure 1) The site ' consists of an abandoned lot with a single building The facihty operated as a former retail gasoline distribution facility The former gasoline underground storage tanks (USTs), the waste oil tank, the 1 diesel tank, and the building location are shown on Figure 4 4_1 Tank Removal and Excavation On April 17, 1991, six USTs were removed from the project site by RESNA Industries, Inc The USTs consisted of one 550-gallon diesel tank, two 2,000-gallon gasoline tanks, one 4,000-gallon gasoline tank, one 10,000-gallon gasoline tank and one 350-gallon waste oil tank (Figure 4) Soil W 195141*art1yl4gr--1995 doc 2 • SN�TH 1