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GROUND ZERO ANALYSIS, INC. ' 1714 Main Street Escalon, California 95320-1927 Telephone (209)838-9888 Facsimile (209)838-9883 APR 2 3 2003 April 22, 2003 ENVIRONMENT HEALTH PERMIT/SERVICES Mr Harlin Knoll San Joaquin County Environmental Health Department 304 East Weber Avenue, Third Floor Stockton, CA 95202 Subject First Quarter 2003 Groundwater Monitoring Report Knowles Property, 1140 W Hammer Lane, Stockton, CA Dear Mr Knoll This report summarizes activities at the subject site (Figure 1) during the first quarter 2003 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) SITE ACTIVITIES Groundwater Monitoring and Sampling An experienced Ground Zero technician measured the depth to groundwater in each site well on February 10, 2003 The depth to groundwater beneath the site ranged from 33 83 feet below the tops of the well casings (btoc) in well MW3 to 35 47 feet btoc in well MW2 Groundwater elevations in site wells rose an average of 3 0 feet between November 12, 2002 and February 10, 2003 The water table beneath the site lies above the screened intervals in wells MW4 and MW5 Groundwater flow was generally toward the east with a calculated gradient of 0 0018 feet per foot, or approximately 9 4 feet per mile A ti et surface map for February 10, 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 a minimum of three well casing volumes of groundwater from monitoring wells MW1, MW3, MW4 and MW5 on February 10, 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 disposal 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 Subsequently the samples were placed in an ice chest refrigerated to a temperature of approximately 4°C r G1GROi3NDZEIKNOWLES HAMIREPORTSIQ1,ARMQM2003 doc