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GROUND ZERO ANALYSIS, INC. R ECEWEDD <br /> 1714 Main Street FEB 19 2004 <br /> Escalon,California 95320-1927 ENVIRONMENT HEALTH <br /> Telephone (209)838-9888 PERMIT/SERVICES <br /> Facsimile (209)838-9883 <br /> February 18, 2004 <br /> Mr Harlin Knoll <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Subject Report of 4th Quarter 2003 Groundwater Monitoring <br /> and Well Installation <br /> Knowles Property, 1140 W Hammer Lane, Stockton, CA <br /> Dear Mr Knoll <br /> This report summarizes activities at the subject site during the fourth quarter 2003 The site location is <br /> presented on Figure 1 Activities conducted during the reporting period included monitoring depth to <br /> water in wells MW1 through MW5, purging and sampling wells MW1, MW4, and MW5, drilling and <br /> installing monitoring well MW9, developing and sampling well MW9, analyzing groundwater samples <br /> for benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons as gasoline <br /> (TPHg), and surveying the wellhead elevation of newly installed well MW9 <br /> SITE ACTIVITIES <br /> Groundwater Monitoring and Sampling <br /> An experienced Ground Zero technician measured the depth to groundwater in wells MW 1 through <br /> MW5 on November 12, 2003 The depth to groundwater beneath the site ranged from 38 85 feet below <br /> the top of the well casing (btoc) in well MW3 to 40 41 feet btoc in well MW2 Groundwater elevations <br /> in wells MW1 through MW5 fell an average of 1 07 feet between August 12, 2003 and November 12, <br /> 2003 The water table beneath the site lies above the screened intervals in wells MW4 and MW5 <br /> Groundwater flow was generally toward the northeast with an average gradient of 0 0028 (approximately <br /> 14 8 feet/mile) A potentiometric surface map for November 12, 2003 is presented on Figure 2 <br /> Monitoring well construction details are summarized in Table 1 Groundwater monitoring data are <br /> summarized in Table 2 <br /> A Ground Zero technician purged at least three well casing volumes of groundwater from monitoring <br /> wells MW1, MW4, and MWS on November 12, 2003 Physical parameters (temperature, specific <br /> conductance, pH and turbidity) were measured and recorded during the purging process All downhole <br /> . equipment was decontaminated prior to and between each use by washing with a solution of laboratory- <br /> grade detergent and then double-rinsing with water Groundwater samples were collected using <br /> G\GROUNDZE\KNOWLES HAM\REP0RMQMR0003\4QM2003 doc <br />