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Quarter Monitoring Report ' January through March 2005 • 8200 N Highway 99, Stockton, CA Page 3 of 8 ' collected from well MW2, which was destroyed on February 28, 2005 under a permit issued by the San Joaquin Environmental Health Department (EHD) A summary of well destruction ' activities is included in Section 4 2 The depth to groundwater was measured in each well on March 16, 2005 prior to any purging Groundwater elevations were calculated by subtracting the measured depth to water from the respective well head elevation The measured depth to groundwater in the A Zone monitoring wells ranged from 67 13 to 68 43 feet below the tops of the well casings (btoc) The depth to t water in groundwater extraction wells were measured at 66 14 feet btoc in well EW1 and 67 51 feet We in well EW2 The extraction wells were not pumping at the time the measurements were taken Groundwater elevations in A Zone monitoring wells ranged from 34 83 to 35 90 feet ' below mean sea level (MSL) Groundwater levels in the A Zone wells, not including the extraction wells, rose an average of 1 78 feet between December 14, 2004 and March 16, 2005 The groundwater level in B Zone wells MW913 and MW 14B measured 66 74 feet btoc and 67 56 feet btoc, respectively Groundwater elevations in the B Zone wells MW913 and MW 14B were calculated to be 35 15 and 35 33 feet below MSL, respectively, an average rise of 1 70 feet between December 14, 2004 and March 16, 2005 The groundwater elevation in C Zone well MW13C was measured at 68 08 feet btoc (35 90 feet below MSL), a rase of 169 feet between December 14, 2004 and March 16, 2005 Groundwater in the A Zone aquifer on March 16, 2005 generally flowed in a northeasterly direction, although a cone of depression is evident around the extraction well EW2 The average groundwater gradient on March 16, 2005 was 0 003 (approximately 17 feet per mile) in the eastern portion of the site and 0 002 (11 feet per male) in the western portion of the site Table 4 summarizes groundwater elevations in site monitoring wells Figure 3 presents a potentiometric surface map generated using the March 16, 2005 monitoring data Attachment C contains field notes 3.2 Groundwater Sampling and Analysis ' An experienced Ground Zero technician purged at least three well casing volumes of water from monitoring wells MW3 through MW 16 and V W 1 prior to sampling The technician measured the temperature, pH and electrical conductivity of the water during the purging process Purged ' groundwater was temporarily contained in appropriately labeled DOT-approved 55-gallon drums in accordance with 49 CFR part 172 and 40 CFR part 262 prior to being processed through the groundwater treatment system Attachment C contains field purge logs ' Groundwater samples were collected after the physical parameters stabilized and water levels in the wells recovered to at least 99% of their respective pre-purged levels Groundwater samples were also collected from the extraction wells EW 1 (MW 1) and EW2 The samples were temporarily stored in an ice chest refrigerated to a temperature of approximately 4'C and delivered under chain of custody protocol to Argon Laboratories (ELAP #2359) for analysis G 1GROUNDZE\TULE$URG%Reports\QMR12005V QM2005 doc