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IICV A SS O C I A T E S I N C Groundwater Flow Direction ' Water level measurements were collected from MW2 through MW 10, and CW on March 18, 2004 Water levels ranged from 24 56 to 28 43 feet below the tops of the well casing elevations, representing an average increase in the water table elevation of approximately 1 02 feet since ' December 2003 The water level data were used to develop a groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, shallow groundwater beneath the site flowed toward the northeast The average hydraulic gradient on March 18, 2004 ' was calculated to be 0 006 ft/ft or approximately 41 ft/mile A summary of groundwater monitoring data is presented in Table 1 ' REMEDIATION SYSTEM MONITORING ACTIVITIES Vapor Extraction System Monitoring The installation and startup of the vapor extraction system located at the site is detailed in ATC's Remediation System Installation Report for the Farmer Property, 610 North Hunter Street, ' Stockton, California, dated April 8, 2003 After the modifications described in the Remediation System Installation Report were made to the system, ATC started the vapor extraction system on December 19, 2002 During the current reporting period, ATC personnel monitored the vapor extraction system on January 28, February 23, and March 26, 2004 ' Parameters monitored in the field included vapor extraction flow rates, hydrocarbon vapor concentrations, groundwater extraction rate, total groundwater discharged to the City of Stockton sanitary sewer, and total hours of system operation Field monitoring data are contained in ' Attachment 3 On January 28, February 23, and March 26, 2004, ATC personnel collected vapor samples from ' wells VW 1, VW2, and from the influent and effluent vapor streams of the vapor extraction system On January 28 and March 26, 2004, ATC personnel collected vapor samples from well VW4 and on February 23 and Mdreh 26, 2004 vapor samples were collected from well MW 1 The samples ' were transported under chain-of-custody documentation to SunStar Laboratories, Inc (ELAP 42250) in Tustin, California and were analyzed for VOCs by EPA method TO-14 ' On January 28, February 23, and March 26, 2004, ATC personnel collected water samples from the groundwater treatment and discharge component of the vapor extraction system Water samples were collected from the influent and effluent of the groundwater treatment system and transported ' under chain-of-custody documentation to Argon Labs for analyses The water samples were analyzed for TPHg by EPA method 801513, BTEX by EPA method 802113, and MTBE, TAME, ' ETBE, DIPE, TBA, 1,2-DCA, and EDB by EPA method 8260B ie s\env aro1625961quartlyll qr-2004 doc 4 1