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Soil gonng and Monitoring Weil Installation Report Page 5 Ranch Market Riverbank CA September 6 2000 4.5.2 Well Development Procedures Each well was developed on August 16, 2000 by surging/bailing and pumping Approximately 10 well casing volumes of groundwater was purged from each well, until pH, temperature, and conductivity readings stabilized Parameters monitored during development, as indicated in the field notes, included pH, conductivity, and temperature (Appendix Q 4.5.3 Groundwater Sampling Procedures All wells were monitored to verify at least 80% recovery prior to sampling Once adequate recovery was observed in the purged wells sampling was conducted A disposable hand bailer was used to collect the groundwater samples All samples were collected in appropriate containers, preserved on ice, and transported under chain-of-custody manifest to Kiff Analytical LLC, in Davis, California for analysis The water samples were analyzed using U S Environmental Protection Agency (EPA) method 8260B for BTEX, TPHg, oxygenates, 1,2-DCA and EDB Chain of Custody manifests are provided in Appendix E 5.0 ANALYTICAL RESULTS 5.1 Results of Soil Sampling Histoncal soil sample laboratory analytical results for the Ranch Market site, including results of samples collected during the assessment in June, July, and August 2000, are summarized in Table 2 and presented on Figure 8 Copies of the analytical data are included in Appendix E The analytical results from soil samples collected at the Ranch Market site indicate petroleum hydrocarbons are present in the soil underlying the location of the former UST pit from 10 to approximately 30 feet bgs The gasoline appears to have migrated laterally from below the tank pit, creating a 10-foot thick smear-zone from 20 to 30 feet bgs, adjacent to the location of the former UST pit and down gradient of the Ranch Market property. The smear-zone is evidenced by reported concentrations above detection limits for benzene, toluene, ethylbenzene,TPHg, and MtBE in borings GP-2 and SB-2, which are not located immediately adjacent to the location of the former UST pit and contain no contamination at depths above the historical groundwater table elevation The maximum TPHg and benzene concentrations reported in soil are 28,100 mg/kg and 183 mg/kg, respectively These concentrations were both from samples collected at 20 feet bgs in boring MW-2 The maximum MtBE concentration reported at the Site was 1 1 mg/kg, from 20 feet bgs in boring SB-1 The two cross sections show the approximate extent petroleum hydrocarbons adsorbed to soil under and adjacent to the former UST pit File R-Welllnstall&M&S rpt doe SECOR International Incorporated