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rc 1117 Lone Palm Avenue, Suite Modesto, CA 953511 www.atcar>sociates.com 209-579-2221 A S S O C I A T E S I N C . Fax 209-579-2225 vironmental,Geotechnical and Materials Engineers Shallow groundwater flow beneath the site was generally flowed in a radial pattern towards JLM3. Recent historical groundwater flow direction has generally been toward the southeast and east. However, water level data collected on August 30, 2005, indicated a similar radial flow pattern. A summary of groundwater monitoring data is presented in Table 1. ANALYTICAL RESULTS None of the analytes of interest were detected in the groundwater samples collected from wells JLM4 and JLM14 through JLM19. TPHg was detected in the groundwater samples collected from wells JLM3, JLM5, and JLM13 at concentrations of 410 micrograms per liter (µg/L), 150 µg/L, and 1,100 gg/L, respectively. Benzene was detected in the groundwater samples collected from wells JLM3, JLM5, and JLM13 at concentrations of 14 µg/L, 1.7 pg/L, and 110 µg/L, respectively. Toluene was detected in the groundwater sample collected from JLM13 at a concentration of 5.2 µg/L. Ethylbenzene was detected in the groundwater samples collected from JLM3, JLM5, and JLM13 at concentrations of 40 µg/L, 11 gg/L, and 110 µg/L, respectively. Xylenes were detected in the groundwater samples collected from wells JLM 3 and JLM13 at concentrations of 48 µg/L and 49 gg/L, respective. MTBE was detected in the groundwater samples collected from wells JLM3, JLM5, and JLM12 at concentrations of 4.0 µg/L, 2.7 µg/L, and 1.6 µg/L, respectively. 1,2-DCA was detected in the groundwater samples collected from wells JLM3, JLM5, and JLM13 at concentrations of 6.0 µg/L, 14 pg/L, and 370 gg/L,respectively. • TPHd, ETBE, DIPE, TAME, TBA, and EDB were not detected at or above the laboratory reported detection limits in any of the samples. Analytical results of groundwater samples are summarized in Table 2. Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2. Isoconcentration maps depicting benzene, MTBE, and 1,2-DCA concentrations in the groundwater samples collected during the first quarter 2006 are shown on Figures 4, 5, and 6,respectively. GEOTRACKER DATA UPLOAD The depth to water and laboratory data associated with the first quarter 2006 sampling event were submitted electronically to the State Water Resources Control Board (SWRCB) Geotracker database (confirmation numbers 6938999772 and 4587912678, respectively). Documentation of the data submittal is contained in Attachment 3. CONCLUSIONS The laboratory analytical results of the groundwater samples collected from the monitoring wells in March 2006 are generally consistent with recent historical analytical results of groundwater samples collected from these wells. None of the analytes of interest were detected in the groundwater samples collected from wells JLM4 and JLM14 through JLM19. This represents the first time since March 2003 that petroleum hydrocarbons were not detected in samples collected from well JLM4. Petroleum hydrocarbons have never been detected in samples collected from JLM14 through JLM19. • Petroleum hydrocarbon concentrations detected in the groundwater samples collected from JLM3 and JLM12 increased with respect to the previous sampling event. Petroleum hydrocarbon s:\envimmmta1\28589\reports\2006 I QR.doc 3