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• GROUND ZERO ANALYSIS, INC. 1714 Main Street Fscalon,California 95320-1927 Telephone (209)838-9888 Facsimile (209)838-9883 September 24, 2003 Mr Harlin Knoll San Joaquin County Environmental Health Department 304 East Weber Avenue, Third Floor Stockton, CA 95202 Subject Third Quarter 2003 Groundwater Monitoring Report Knowles Property, 1140 W Hammer Lane, Stockton, CA Dear Mr Knoll This report summarizes activities at the subject site during the third quarter 2003 The site location is presented on Figure 1 Activities conducted during the reporting period included monitoring depth to water in all site wells, purging and sampling wells MW1, MW2, MW3, MW4 and MW5, and analyzing groundwater samples for benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons as gasoline(TPHg) SITE ACTIVITIES Groundwater Monitoring and Sampling An experienced Ground Zero technician measured the depth to groundwater in each site well on August 12, 2003 The depth to groundwater beneath the site ranged from 37 81 feet below the top of the well casing(btoc) in well MW3 to 39 31 feet btoc in well MW2 Groundwater elevations in site wells fell an average of 4 82 feet between May 27, 2003 and August 12, 2003 The water table beneath the site lies above the screened intervals in wells MW4 and MW5 Groundwater flow was generally toward the northeast with a average gradient of 0 0028 feet per foot, or approximately 15 feet per mile A potentiometric surface map for August 12, 2003 is presented on Figure 2 Monitoring well construction details are summarized in Table 1 Groundwater monitoring data are summarized in Table 2 A Ground Zero technician purged at least three well casing volumes of groundwater from monitoring wells MW 1, MW2, MW3, MW4 and MW5 on August 12, 2003 Temperature, specific conductance, and pH were measured and recorded during the purging process All downhole equipment was decontaminated prior to and between each use by washing with a solution of laboratory-grade detergent and then double-rinsing with water Groundwater samples were collected using dedicated disposable bailers after physical parameters stabilized, and water levels recovered to at least 80% of pre-purged levels The samples were decanted into 40-m1 glass vials preserved with dilute hydrochloric acid The samples were subsequently placed in an ice chest refrigerated to a temperature of approximately 4°C G IGROUNDZEIKNOWLFS HAMIREPORTSIQMR13QM2003 doc