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Geo(ogua(TeckucsI" Page 5 Groundwatei Monitoring Report Project No 770 2 September 24, 2003 ' 1.3 Laboratory Analyses ' The groundwater samples collected on June 18, 2003, were delivered to Sherwood Lab (Department of Health Services Certification No 1400), of Hilmar, California, for analysts ' Shei wood analyzed the seven monitoring well groundwater samples for m'f 6�s • Benzene, Toluene, Ethyl Benzene, and Xylene(BTEX) by EPA method 8020 yL ' • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M) • TEPH- Diesel and Motoi Oil by EPA method 3500/8100(M) The detection limits for the above analyses are listed in Table 3 of Appendix A while the ' laboratory analytical results are presented in Appendix B As required under AB2886, the groundwater elevation and laboratory data were submitted electronically to GeoTracker on August 22, 2003 - confirmation numbers 3637039005 & 4082124769 2.0 FINDINGS AND DISCUSSION The results of the groundwater sample analysis indicate the following • The ieversal of groundwater direction by 1800 in the deeper aquifer for the April and May 2003 sounding events is anomalous to the historical data The deeper aquifer has been monitored by three wells (MW-104, MW-105 and MW-106) since June 2002 and the other eight events all displayed an easterly trend to groundwater direction It is noted that the gradients for these two events were higher than normal suggesting that off site sources are influencing the aquifer A well receptor survey was completed for the site to January 2001 and two agricultural wells were identified approximately 1600 feet west of the site (see Map 1, Table 1 — Appendix D) If these wells were operated during the months in question, it is possible that the Marct site was within the cone of ' depression created by the well pumping The shallow aquifer did not reverse during this period and this may be due to the domestic wells to the southeast of the site that may be screened shallower than the agricultural wells and exert a primary influence on the water table that is easterly • Diesel range petroleum hydrocarbons were detected in five of the site's eleven monitoring wells • Well MW-5 contained 3200 µg/l diesel and remains the most severely impacted well The reversal in groundwater direction discussed above may be the reason that the core / plume is displaced from the location of the former UST • Gasoline range petroleum hydrocarbons (TPH-G) were not detected in any of the wells for this event Several wells have had at least one event in which TPH-G was detected