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GeofoBrcaC?ecfiisus In- Page 5 Soil&Groundwater Investigation Report l Ted Peters-UST Project No 640 2 • November 3, 1999 ' 3.0 RESULTS OF INVESTIGATION The analytical results and field observations are discussed below Summary analytical data is ' included in Appendix A, boring logs are included in Appendix B A site map with soil boring and monitoring well locations is included as Figure 2 ' 3.1 Analytical Results 3.11 Soil Sample Analysis In summary ' • Of the eleven soil samples submitted for analysis, only one tested positive for low levels of contaminants The soil sample collected from MW-2 at 5 5 to 6 feet bgs, contained Ethyl Benzene, Xylene, and TPH-G ' • Samples collected from SB-1, SB-2, MW-1 and MW-2 contained low levels of TTLC- Lead • None of the oxygenated fuel compounds were detected in any of the samples ' The geology as it relates to the analytical data is discussed to the conclusion section below Table 1 in Appendix A contains a full summary of the analytical data and the laboratory data sheets are included in Appendix C ' 3.1.2 Groundwater Sample Analysis After development of new monitoring wells, a groundwater monitoring was conducted on I� July 26, 1999 and samples were submitted for analysis of TPH-G, BTEX and the oxygenated fuel compounds The results of the groundwater analysis are included as Table 2 in Appendix A The analytical data reports are included in Appendix C I In summary • Low concentrations of Toluene, Ethyl Benzene, Xylene and TPH-G were detected in the groundwater sample collected from MW-1 ' • Low concentrations of Ethyl Benzene, Xylene and TPH-G were detected in the groundwater sample collected from MW-2 • MW-3 was non-detect for all analytes I • All wells were non-detect for the oxygenated fuel compounds 3.2 Site Hydrology I On September 22, 1999 the "top of casing" for each monitoring well was surveyed into the City of Manteca Benchmark, No 45 by Spencer Land Surveying I A site-specific groundwater gradient and bearing was calculated from the depth to water measurements taken in MW-1, MW-2 and MW-3 during the groundwater monitoring event The gradient was 0 0014 ft/ft flowing N701W The average groundwater elevation in the three wells was 14 05 feet above mean sea level A gradient was also calculated from the three wells installed at the back of the site to investigate the AST area The gradient in this area was S49°W at 0 004 ft/ft At this time it is not understood why there is a difference to gradient directions and slopes on the two parts of the site Further monitoring may help to further understand the situation I I