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GROUND ZERO ANALYSIS, INC. <br /> 1714 Main Street <br /> Escalon,California 95320-1927 <br /> ` Telephone: (209)838-9888 <br /> Facsimile: (209)838-9883 <br /> A <br /> {�Q March 5, 1999 <br /> 1 Mr Harlin Knoll <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Subject Fourth Quarter 1998 Site Status Report <br /> Knowles Property, 1140 W Hammer Lane, Stockton, California <br /> Dear Mr Knoll <br /> This report summanzes the fourth quarter 1998 activities at the subject site (Figure 1) Activities during <br /> the quarter included monitoring depth to water in all site wells, purging and sampling wells MW 1, MW4 <br /> MW5, and MW8, analyzing the samples for total petroleum hydrocarbons as gasoline (TPHg), benzene, <br /> toluene,ethylbenzene, and total xylenes (BTEX), and conducting a potential receptor survey <br /> GROUNDWATER MONITORING <br /> Groundwater monitoring was performed on November 5, 1998 The depth to groundwater beneath the site <br /> ranged from 34 15 to 36 27 feet below grade Overall, groundwater elevations rose an average of 0 56 feet <br /> since August 6, 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 1 The groundwater <br /> flow direction at the time of measurement was generally to the southeast at a gradient of 0 007 ft/ft A <br /> groundwater gradient map for November 5, 1998 is presented on Figure 2 Groundwater monitoring data <br /> are summarized in Table 2 <br /> GROUNDWATER SAMPLING AND ANALYSIS <br /> Monitoring wells MWl, MW4, MW5, and MWS were sampled on November 5, 1998 <br /> Approximately four well casing volumes of water were purged from each well pnor to sampling <br /> The purged water is currently contained on site in labeled drums approved by the Department of <br /> Transportation (DOT) pending disposal Copies of purge logs are in Attachment A <br /> The groundwater samples were submitted to Argon Laboratories (ELAP (#1873) for analysis of TPHg and <br /> 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 20 parts per billion <br /> (ppb), <0 5 ppb, 23 ppb, 18 ppb, and 1,000 ppb, respectively MW5 contained BTEX and TPHg at <br /> /knowles ham/reports/4gm1998 doc <br />