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GROUND ZERO ANALYSIS, INC. <br /> C ^lrT n r <br /> 1714 Main Street <br /> ' - + UI <br /> Escalon,California 95320-1927 <br /> Telephone- (209)838-9888 <br /> Facsimile: (209)838-9883 <br /> October 16, 1998 <br /> Mr Harlin Knoll <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 East Weber Avenue, Tlurd Floor <br /> Stockton, CA 95202 <br /> Subject Third Quarter 1998 Site Status Report <br /> Knowles Property, 1140 W Hammer Lane, Stockton, California <br /> Dear Mr Knoll <br /> This report summarizes the third quarter 1998 activities at the subject site (Figure 1) Activities during the <br /> quarter included monitoring depth to water in all site wells, purging and sampling wells MW 1, MW2, <br /> MW3, MW4, MW5, and MW8, as well as analyzing the samples for total petroleum hydrocarbons as <br /> gasoline (TPHg), benzene,toluene, ethylbenzenc, and total xylenes (BTEX) <br />• GROUNDWATER MONITORING <br /> Groundwater monitoring was performed on August 6, 1998 The depth to groundwater beneath the site <br /> ranged from 34 73 to 36 77 feet below grade Overall, groundwater elevations fell an average of 2 23 feet <br /> since May 19, 1998 The water table beneath the site lies above the tops of the screened intervals for wells <br /> MW4 through MW8 Monitoring well construction details are summarized in Table 3 The groundwater <br /> flow direction at the time of measurement was generally to the southeast A groundwater gradient map for <br /> August 6, 1998 is presented on Figure 2 Groundwater monitoring data are summarized in Table 1 <br /> GROUNDWATER SAMPLING AND ANALYSIS <br /> Monitoring wells MW 1, MW2, MW3, MW4, MW5, and MW8 were sampled on August 6, 1998 <br /> Approximately three to six well casing volumes of water were purged from each well prior to sampling <br /> The purged water was temporarily contained on site, and placed in labeled drums approved by the <br /> Department of Transportation for the storage of liquid wastes, and were subsequently transported to <br /> Evergreen Oil, Inc in Newark, California Copies of purge logs and the non-hazardous waste manifest are <br /> included in Attachment A <br /> The groundwater samples were submitted to Argon Laboratories (ELAP #1873) for the analysis of TPHg <br /> and BTEX utilizing EPA methods 8015 modified and 8020, respectively <br /> Groundwater samples collected from well MW 1 and MW5 contained elevated levels of petroleum <br /> hydrocarbons BTEX and TPHg were detected in well MW 1 at concentrations of 52 parts per billion <br /> (ppb), c0 5 ppb, 24 ppb, 48 ppb, and 1,200 ppb, respectively MW5 contained BTEX and TPHg at <br /> groundzelknowles ham/reporls/3gm1998 doc <br />