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f f . GROUND ZERO ANALYSIS, INC. .. r 1714 Main Street '_ J Escalon,California 95320-1927 Telephone: (209)838-9888 Facsimile: (209)838-9883 July 23, 1999 Mr Harlin Knoll San Joaquin County Public Health Services Environmental Health Division 304 East Weber Avenue, Third Floor Stockton, CA 95202 Subject Site Status Report, Second Quarter 1999 Knowles Property, 1140 W Hammer Lane, Stockton, California Dear Mr Knoll This report summarizes the second quarter 1999 activities at the subject site (Figure 1) Activities during the quarter included monitoring depth to water in all site wells, purging and sampling wells NMI, MW4, MWS, and MW8, and analyzing the samples for benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons as gasoline (TPHg) GROUNDWATER MONITORING Groundwater monitoring was performed on May 11, 1999 The depth to groundwater beneath the site ranged from 30 23 to 32 32 feet below grade Overall, groundwater elevations rose an average of 0 55 feet since February 1999 The water table beneath the site lies above the screened intervals for all wells except MW3 Monitoring well construction details are summarized in Table 1 The groundwater flow direction at the time of measurement was generally to the southeast at a gradient of 0 0055 ft/ft A groundwater gradient map for May 11, 1999 is presented on Figure 2 Groundwater monitoring data are summarized in Table 2 GROUNDWATER SAMPLING AND ANALYSIS Monitoring wells MW 1, MW4, MWS, and MW8 were sampled on May 11, 1999 A minimum of three well casing volumes of water was purged from each well prior to sampling The purged water from this event is currently contained on site in labeled drums approved by the Department of Transportation (DOT) pending disposal Copies of purge logs are included in Attachment A t! /knowles harn/reports/2gm1999 doc