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lot IA ATC Associates Inc YVJ%TC 1117 Lone Palm Avenue, Suite B Modesto, Cakforma 95351 209-579-2221 • ASSOCIATES i NC fax 209-579-2225 On September 11 and 12, 2003, a 500-gallon capacity used oil UST was excavated and removed from the site respectively, by Walton Engineering, Inc Petroleum hydrocarbons and metals were detected in a soil sample collected from below the former location of the UST from a depth of approximately seven feet bgs Refer to Grayland Environmental's Underground Storage Tank and Fuel Dispenser Removal Report, dated October 16, 2003, for more information In September 23 and 24, 2003, H2OGEOL collected groundwater samples from MW 1 and MW4 through MW8 Petroleum hydrocarbons were detected in groundwater samples collected from these wells The reported groundwater flow direction was to the north Refer to 112OGEOL's Third Quarter, 2003 Groundwater Monitoring Report, dated October 31, 2003, for more information SAMPLING ACTIVITIES On August 19, 2004, ATC personnel collected groundwater samples from monitoring wells MW 1 and MW4 through MW8 Monitoring wells MW2 and MW3 are sampled annually The locations of the wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured and turbidity was visually observed in groundwater purged from the monitoring wells and recorded Approximately three well casing volumes were purged from each monitoring well prior to sampling The wells were iallowed to recover and samples were collected from each well using disposable polyethylene bailers The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc Environmental Laboratory Accreditation Program (FLAP) Cert No 2359, in Ceres, California for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg) utilizing EPA method 8015M, benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8021B, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di- isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2- dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) utilizing EPA method 8260B Groundwater well purge and sample logs are contained in Attachment 1 GROUNDWATER FLOW DIRECTION Water levels were measured in wells MW1 through MW8 on August 19, 2004 Depth to water in the shallow aquifer ranged from 5 78 to 7 80 feet below the tops of the well casmg elevations, representing an average decrease in the shallow water table elevation of approximately 1 15 feet since March 2 04 The water level data were used to develop the groundwater elevation contour map (Figure YX Shallow groundwater flow in the uppermost aquifer beneath the site is towards the north The average hydraulic gradient on August 19, 2004 was calculated to be 0 0026 ft/ft or approximately 14 ft/mile A summary of groundwater monitoring data is presented in Table 1 Yq I s lenvuumeenW\25847M371rep \39r-2004 doc 3 I