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k'Tj KLEINFELDER i I b CONCLUSIONS AND RECOMMENDATIONS On.July 29, 30, 31, and August 1, 2003, 10 monitoring wells and 3 piezometers were purged and sampled. Water samples obtained from each location were submitted for chemical analysis. Additionally, on September 3 and 9, 2003, two supplemental groundwater samples 'were collected from select monitoring wells to assess the ozone sparge system recently activated at the site. Based on the data obtained during our assessment, the following conclusions and recommendations have been formulated: 1. Groundwater flow direction at the site is estimated to be towards the east/southeast at approximately 0.0004 ft./ft. This is consistent with the recent groundwater data collected at the site. 2. Based on the results of the groundwater sampling it appears that the groundwater quality has remained relatively consistent with the past sampling events. The results showed no TPH-g, benzene, toluene, ethylbenzene, xylene, EDB, TBA, DIPE, ETBE, or TAME detected in any of the monitoring wells outside of the former service station footprint sampled this quarter. The concentrations of the above listed analytes has remained consistent with past monitoring events. I TPH-g was detected in'5 groundwater samples analyzed from MW-1, MW-2, NPI- 70', 80', and 90' ranging from 340 µg11 to 160,000 µg/1. Similarly, BTEX compounds were detected in the same groundwater samples collected ranging from 1.7 Ag/1 (Toluene) to 46,000 µg/1 (Toluene). 1,2-DCA was detected in 7 of the 13 groundwater samples. The detected concentrations ranged from 0.51 .µg/1 (MW-DIS-42) to 3,100 µg/1 (NPI-80'). The detected concentration of 0.51 gg/l was just above the laboratory reporting limit of . 0.50 µg/l. The detected concentrations of 1,2-DCA exceeded the Primary Maximum Contaminant Level (PMCL) for 1,2-DCA of 5 µg/l in five of the samples (MW-DIS-1, NPI-90', NPI-80', MW-DIS-11s, MW-DIS-15). 1 EDB was detected in the groundwater samples collected from NP1-80', and NPI- 90' with concentrations of 1,200 gg/l and 90 µg11 respectively. MTBE was detected in MW-DIS-14s with a concentration of 0.64 µg11. The Primary Maximum Contaminant Level (PMCL) for MTBE is 13 µg/1 and the Secondary Maximum Contaminant Level (SMCL) for MTBE is 5 gg/l. The detected concentration of MTBE in MW-DIS-14s does not exceed the PMCL or the SMCL for MTBE this quarter. There were no detectable concentrations at or above the laboratory reporting limit for the oxygenates MTBE, DIPE, ETBE, and TAME in the groundwater sample collected from MW-DIS-15 this quarter. PMCLs are derived 12280.MON/ST03R1392 Page 12 of 14 2003,Kleinfelder,Inc October 13,2003