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GROUND ZERO ANALYSIS, INC. 1714 Main Street Escalon, California 95320-1927 Telephone (209)838-9888 Facsimile (209)838-9883 October 24, 2002 Mr Harlin Knoll San Joaquin County Environmental Health Department 304 East Weber Avenue, Third Floor Stockton, CA 95202 Subject Third Quarter 2002 Groundwater Monitoring Report Knowles Property, 1140 W Hammer Lane, Stockton, CA Dear Mr Knoll iThis report summarizes activities at the subject site (Figure 1) during the third quarter 2002 Activities conducted during the reporting period included monitoring depth to water in all site wells, purging and sampling all site wells, analyzing the samples for benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons as gasoline (TPHg), and evaluating the feasibility of utilizing ozone infection for remediating groundwater contamination at the site SITE ACTIVITIES Groundwater Monitoring and Sampling An experienced Ground Zero technician measured the depth to groundwater in each site well on August 16, 2002 The depth to groundwater beneath the site ranged from 36 38 feet below ground surface (bgs) in well MW3 to 37 86 feet bgs in well MW2 Groundwater elevations in site wells fell an average of 4 51 feet between May 21, 2002 and August 16, 2002 The water table beneath the site lies above the screened intervals in wells MW4 and MW5 Groundwater flow was in a northeasterly direction with a calculated gradient of 0 0024, or approximately 13 feet per mile A potentiometnc surface map for August 16, 2002 is presented on Figure 2 Monitoring well construction details are summarized in Table 1, and groundwater monitoring data are summarized in Table 2 . The technician purged a rmmmum of three well casing volumes of groundwater from monitoring wells MW1 through MW5 on August 16, 2002 Temperature, specific conductance, and pH were G 11Data1GR0UNDZ9IKN0WLES 1JAMgRfiP0RTS\QMR\3QM2002 doc