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y � 30 May 2004 AGE-NC Project No 02-0962 Page 2 of 10 ' alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977) Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basin 5-22) The estimated depth to ground water at the site is approximately 20 feet below surface grade(bsg)based on information from quarterly monitoring events performed by AGE at the adjacent Nomellim Construction Company, the ground water elevation is estimated at approximately 10 to 12 feet below mean sea level and ground water flows generally towards the east/southeast However, this may be greatly modified by local recharge and discharge patterns 2 2 UNDERGROUND STORAGE TANK PIPING REMOVAL The following information was obtained from the property owner It is AGE's understanding that in February 2003 UST upgrade activities and excavation(performed • by Fillner Construction) of UST sumps, fuel dispensers and associated piping occurred Excavated soil was stockpiled on site for evaluation and transported to Forward Landfill for disposal Soil samples were collected from the floor of the piping excavation, soil stockpiles, and fuel dispenser excavation and analyzed at Cal Tech Laboratories, a California DHS certified laboratory, for total petroleum hydrocarbons quantified as gasoline(TPH-g),total petroleum hydrocarbons quantified as diesel(TPH-d), benzene, toluene, ethylbenzene, and xylenes (BTEX), and fuel oxygenated compounds-methyl tertiary butyl ether- (MTBE), dnsopropyl ether (DIPE), t-amyl methyl ether (TAME), t-butyl alcohol (TBA), 1,2,-dichloroethane (1,2-DCA) and 1,2-dibromoehtane (EDB) The laboratory analysis detected BTEX, MTBE, TPH-g and TPH-d in 14'of 25 analyzed samples 1 from the former piping location and fuel dispensers Analytical results of soil samples are' ' summarized in Table 1, Figure 2 depicts the approximate location of the sample collection points 4 , On 30 and 31 October 2003, AGE sampled soil and ground water at the site utilizing Geoprobe ' techniques, as specified in the AGE-prepared Preliminary Site Assessment Work Plan, dated 09 September 2003 Total petroleum hydrocarbons quantified as TPH-g and TPH-d were detected,at concentrations as high as 2,200,000 µLo micrograms per liter TPH-d (B4-gw) in ground water samples collected during site assessment activities,the highest concentration of MTBE,was 15 gg/l,and was measured in a sample from B5-gw The vertical extent of impacted soil has not been defined at the site, laterally the northern, western, and eastern extent of impacted soil has been defined The vertical Advanced GcoEnvironmental,Inc