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§eofogicaf?echnics Inc. Page 4 Groundwater Monitoring Report i Project No. 770.2 4 January 10,2002 i{ 1.3 Laboratory Analyses 1 Thegroundwater samples collected on December 7, 2001 were delivered to Sherwood Lab (Department of Health Services Certification No. 1400), of Hilmar, California, for analysis. Sherwood analyzed the three monitoring well groundwater samples for: • Benzene, Toluene, Ethyl.Benzene, and Xylene (BTEX) by EPA method 602 f • Total Petroleum Hydrocarbons as Gasoline (TPH-G)by EPA method 5030/8015(M) 1 • TEPH-Diesel and Motor Oil by EPA method 3510/8015(M) The detection limits for the above analyses are listed in Table 2 of Appendix A while the lab analytical results are presented in Appendix B. GTT attempted to submit the laboratory data electronically to GeoTracker on December 28, 2001 as required under AB2886. However, the GeoTracker program indicated that the data contained computer forinat errors, which GTI is in the process of correcting. 1 2.0 FINDINGS AND DISCUSSION The results of the groundwater sample analysis indicate the following: • Diesel range petroleum hydrocarbons were detected in four of the site's seven monitoring wells. • Well MW-5 contained 9,550 µg/l TPH-D and this is the highest level detected since the well's installation in August 2000. • Minor BTEX constituents are present at levels ranging from <0.4 — 4.1 µg/1 in wells MW-4 and MW-6. i • Motor oil range petroleum hydrocarbons were not present in any of the groundwater samples at concentrations above the laboratory reporting limits. • 'Gasoline range petroleum hydrocarbons were not present in any of the groundwater samples at concentrations above the laboratory reporting limits. Four of the wells contained TPH-G for the previous September 2001 event only: MW-1, MW-4, MW-6 and MW-105. • Deep well MW-105 di&not contain contaminant concentrations above the laboratory reporting limits. • The lateral extent of the diesel groundwater plume is currently undefined due to the i continuing fluctuations in groundwater direction. • The vertical extent of the.plume is intermittently defined by MW-105. t An examination of the contaminant and groundwater direction data doesn't reveal any obvious trends. A consistent factor previously noted in the investigation was the increase in diesel concentrations in well MW-5; see Figure 4- MW-5: TPH-D vs. Groundwater !