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U 4� ATC Associates Inc VA 1117 Lone Palrn Avenue, Suite B • (: %TC Modesto, California 95351 209-579-2221 A s s o c i a T E s i N o Fax 209-579-2225 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 GROUNDWATER SAMPLING ACTIVITIES On March 4, 2005, ATC personnel collected groundwater samples from MW1 through MW10 and the domestic well effluent 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 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 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 A sample from this well was taken at the wellhead 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 (Environmental Laboratory Accreditation Program Certification No 2359) in Ceres, California for chemical analyses of TPHg utilizing EPA Method 8015B, benzene, toluene, ethylbenzene, xylenes (BTEX) and methyl tertiary butyl ether (MTBE) utilizing EPA Method 8021B If MTBE was detected by EPA Method 802113, the groundwater sample was subsequently analyzed for MTBE, ethyl tertiary butyl ether (ETBE) dl-isopropyl ether (DIPS), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2-dlchloroethane (1,2-DCA), and 1,2- dibromoethane (EDB) utilizing EPA Method 8260B to confirm the results Groundwater well purge and sample logs are contained in Attachment 1 GROUNDWATER FLOW DIRECTION Water levels were measured in MW1 through MW10 and DW on March 4, 2005 Water levels in the shallow aquifer (as measured in MW 1 through MW10) ranged from 66 54 to 68 03 feet below the tops of the well casing elevations, representing an average increase in the shallow water table elevation of approximately 3 39 feet since December 2004 The water level in DW was 69 06 feet below the top of well casing The water level data from MW1 through MW10 were used to develop the groundwater elevation contour map (Figure 3) Shallow groundwater in the uppermost aquifer beneath the site flowed variably towards the south-southeast The average hydraulic gradient on March 4, 2005 was calculated to be 0 002 ft/ft or approximately 10 6 • ft/mile A summary of groundwater monitoring data is presented in Table 1 S 1[63931REPORTSl l stqtr-2005 doc 3