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3 J METHODS AND PROCEDURES <br /> The sampling rationale is as follows. This site has fine- <br /> WN textured sods with associated high ion exchange capacities, <br /> therefore the lead is expected to have adsorbed onto the <br /> �_. soil and not penetrated very deeply. In contrast, the <br /> volatile organic fractions of gasoline would be more mobile <br /> than lead Therefore, utilizing the presence or absence of <br /> the volatile petroleum hydrocarbons for contamination <br /> indication in the field should be sufficiently conservative <br /> to delineate the lead contaminated zone at the site. <br /> Confirmation is provided by the laboratory analyses of the <br /> soil samples. <br /> To assess the contribution of the former underground tanks <br /> r to soil contamination at the site, WaterWork drilled, <br /> logged, and sampled additional soil borings around the <br /> former tank location (SB1, SB2, SB3, SB4, 385 ) as shown on <br /> Figure 3. Underground Service Alert was notified prior to <br /> commencempnt of drilling activities. <br /> F <br /> Work on the site eras conducted on December 8, and 11, 1989. <br /> San Joaquin County Public Health Services Environmental <br /> Health Division was notified to allow observation of boring <br /> abandonment procedures . Drilling was conducted by a <br /> qualified driller ander a C57 license using a hollow stem <br /> auger drill rig. <br /> Drill cuttings were logged continuously for characterization <br /> of contamination and soil type using the Unified Soil <br /> Classification System. Descriptions of soils encountered <br /> were recorded on boring/well logs and included in Appendix <br /> A within this assessment report. Soil samples were <br /> collected from each boring at five foot intervals. Sample <br /> collection began at a depth of five feet, except within the <br /> former tank excavation where sample collection began at ten <br /> feet, which was previously discussed with County staff. <br /> IM <br /> Soil samples sutmitted for analysis were selected based on <br /> obvious signs of contamination (i.e. olfactory detection and <br /> soil discoloration) . The sample indicating the highest <br /> contamination was analyzed to determine actual contamination <br /> Levels. Samples were collected, preserved and transported <br /> under chain-of-custody in accordance with WaterWork' s Soil <br /> Sampling Protocol (Appendix B) . Select samples were <br /> analyzed for benzene, toluene and xylenes, and ethylbenzene <br /> ( STXE), total petroleum hydrocarbons (TPH) as gasoline, and <br /> organic lead by appropriate EPA and DHS methodologies. FOL <br /> Environmental laboratories assisted in sample colle. tion and <br /> performed the analyses. <br /> The soil cuttings were covered with 5 mil plastic on-site. k)L0 <br /> Soil cuttings will be properly disposed of in a timely and <br /> appropriate manner after reviewing the analytical results, <br /> The field investigation was conducted under the direct <br /> 5 <br />