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it sl ATC Associates Inc 1117 Lone Palm Aven=, Suite B Modesto, California 95351 209-579-2221 %TC • ASSOCIATE S INC fax 209-579-2225 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 to groundwater samples collected from these wells The reported groundwater flow direction was to the north Refer to H2OGEOL's Third Quarter, 2003 Groundwater Monitoring Report, dated October 31, 2003, for more information In a letter dated November 14, 2003, the EHD indicated that the proposed scope in the H2OGEOL workplan was not adequate or necessary The EHD requested that a workplan be prepared in the context of a site conceptual model that includes analytical data collected during removal of a waste oil tank from the site in September 2003 The requested workplan was submitted by ATC on February 2, 2004 SAMPLING ACTIVITIES I On December 1, 2004, ATC personnel collected groundwater samples from monitoring wells MWI through MW8 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 allowed 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 gasolene (TPHg) utilizing Environmental Protection Agency (EPA) �o� 8015M, benzene, toluene, �„ 5 ethylbenzene, and xylenes (BTEX) utilmng EPA Method �, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (D1PE), 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 MW through MW8 on December 1, 2004 Depth to water in the shallow aquifer ranged from 5 25 to 7 31 feet below the tops of the well casing elevations, representing an average increase in the shallow water table elevation of approximately 0 5 feet since August 2004 The water level data were used to develop the groundwater elevation contour map (Figure 3) Shallow groundwater flow in the uppermost aquifer beneath the site is towards the northeast The average hydraulic gradient on December 1, 2004 was calculated to be 0 0022 s Ienva-mnenW\2584710037Vcports�3gr-2404 dm 3