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rR <br /> GROUND ZERO ANALYSIS, INC. <br /> 1714 Main Street <br /> Escalon,California 95320-1927 <br /> Telephone (209)838-9888 <br /> Facsimile (209)838-9883 <br /> January 20, 2003 <br /> Mr Harlin Knoll <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Subject Fourth Quarter 2002 Groundwater Monitoring Report <br /> Knowles Property, 1140 W Hammer Lane, Stockton, CA <br /> Dear Mr Knoll <br /> This report summarizes activities at the subject site (Figure 1) dunng the fourth quarter 2002 Activities <br /> conducted during the reporting period included monitoring depth to water in all site wells, purging and <br /> sampling all site wells, and analyzing the samples for benzene, toluene, ethylbenzene, total xylenes <br /> (BTEX), and total petroleum hydrocarbons as gasoline (TPHg) <br /> . SITE ACTIVITIES <br /> Groundwater Monitoring and Sampling <br /> An experienced Ground Zero technician measured the depth to groundwater in each site well on <br /> November 12, 2002 The depth to groundwater beneath the site ranged from 36 86 feet below ground <br /> surface (bgs) in well MW3 to 38 43 feet bgs in well MW2 Groundwater elevations in site wells fell an <br /> average of 0 53 feet between August 16, 2002 and November 12, 2002 The water table beneath the site <br /> lies above the screened intervals in wells MW4 and MW5 Groundwater flow was in a northeasterly <br /> direction with a calculated gradient of 0 0018, or approximately 10 feet per mile A potentiometric <br /> surface map for November 12, 2002 is presented on Figure 2 Monitoring well construction details are <br /> summarized in Table 1, and groundwater monitoring data are summarized in Table 2 <br /> A Ground Zero technician purged a minimum of three well casing volumes of groundwater from <br /> monitoring wells MWI, MW4 and MW5 on November 12, 2002 Temperature, specific conductance, <br /> and pH were measured and recorded during the purging process All downhole equipment was <br /> decontaminated prior to and between each use by washing with a solution of laboratory-grade detergent <br /> and then double-rinsing with water <br /> Groundwater samples were collected using dedicated, disposal bailers after physical parameters stabilized <br /> and water levels recovered to at least 80% of pre-purged levels The samples were decanted into 40-m1 <br /> glass vials preserved with dilute hydrochloric acid and placed in an ice chest refrigerated to a temperature <br /> of approximately 4°C The samples were transported to Argon Laboratories (ELAP #2359) under chain <br /> of custody protocol and analyzed for TPHg and BTEX utilizing EPA methods 8015M and 8020, <br /> G 1Data1GROUNDZE1KNOWLES HAMIREPORTSIQMR14QM2002 doe <br />