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A S S O C I A T E S I N C On July 21, 2003, ATC conducted a 5-hour groundwater pump test by extracting groundwater at a generally constant rate from the domestic well on site The extracted groundwater was sampled near the beginning and end of the test, and stored temporarily onsite in a 5,000-gallon polyethylene tank The details and results of the CPT borings and groundwater extraction test are described in ATC's Summary Report of Additional Subsurface Investigation, Pacific Coast Recreation, 3755 Munford Avenue, Stockton, California, dated July 12, 2004 SAMPLING ACTIVITIES On June 22, 2004, ATC personnel collected groundwater samples from monitoring wells MW 1 through MW 10 and domestic well DW The locations of the wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water was measured in the monitoring wells and pH, electrical conductivity, and temperature were measured in groundwater purged from the monitoring wells and recorded Approximately three well casing volumes were purged from each monitoring well prior to sampling The monitoring wells were allowed to recover and samples were collected from each well using disposable polyethylene bailers The domestic well was sampled utilizing the dedicated domestic well pump system and sample tap at the well head After the groundwater samples were collected, dissolved oxygen was measured in groundwater purged from each monitoring well The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc (ELAP Cert No 2359) in Ceres, California for chemical analysis of TPHg utilizing EPA Method 801513, benzene, toluene, ethylbenzene, xylenes (BTEX) and methyl tertiary butyl ether (MTBE) utilizing EPA Method 8021B Groundwater well purge and sample logs are contained in Attachment 1 GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW 1 through MW 10 on June 22, 2004 Water levels in the shallow aquifer ranged from 67 34 to 69 79 feet below the tops of the well casing elevations, representing an average decrease in the shallow water table elevation of approximately 1 91 feet since March 2004 The water level data were used to develop the groundwater elevation contour map (Figure Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed generally towards the southwest The average hydraulic gradient on June 22, 2004 was calculated to be 0 005 ft/ft or approximately 23 8 ft/mile A summary of groundwater monitoring data is presented in Table 1 ANALYTICAL RESULTS Groundwater samples collected from wells MW 1, MW2, MW3, MW6, MW7, MW8, and DW • contained the highest concentrations of TPHg and BTEX Groundwater samples collected from wells MW4 and MW 10 also contained detectable concentrations of TPHg and/or BTEX S 1Enviromenta{1163931REPORTS12gr-2004 doe 3