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i GROUND 29RO ANALYSIS, INC- 2291 W. March Lane, Suite 127D ; Stockton, Cahformm 95207 Telephone: (209) 952-3481 Facsande• (209) 952-9892 F � August 29, 1996 Ms Lunda Turkatte i San Joaquin County-Public Health Services i Environmental Health Division 445 North San Joaquin Street 4 PO Box 388 Stockton, CA 95201-0388 Subject Third Quarter 1996 Groundwater Monitoring and Sampling Report Knowles/Roek Property, 102 South Wilson Way, Stockton, California a Dear Ms Turkatte 1 Ground Zero Analysis, Inc (Ground Zero) has prepared this report for groundwater monitoring and sampling performed during the third quarter 1996 at the subject site (Figure 1) Activities during the third quarter of 1996 included monitoring groundwater elevations, purging and sampling groundwater, and analyzing samples for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes(BTEX), and methyl tert-butyl ether(MTBE) E Groundwater monitoring was conducted on August 7, 1996. The depth to groundwater was measured in each well and subtracted from the wellhead elevation to determine groundwater elevation Water levels m the wells rose an average of 0 27 feet since last monitored on April 24, 1996 Groundwater flow was generally easterly at an average gradient of 0 0027 feet per foot A groundwater gradient map generated using the August 7, 1996 monitoring data is shown on Figure 2 Previous reports have included two groundwater gradient maps, one using data from wells shallower than 65 feet and one using data from wells deeper than 65 feet However, groundwater elevations across the site seem to have equilibrated during the reporting period. Recent groundwater monitoring data are summarized in Table 1. Monitoring logs are included in Attachment A Groundwater samples were collected from wells MW 1 through MW 13 on August 7 and 8, 1996. At least three well casing volumes were purged from each well prior to sampling. Physical parameters (pH, conductivity, temperature) were monitored during purging and allowed to stabilize prior to sampling Purged water was contained in 55-gallon drums approved by the Department of Transportation and remains on site pending analytical results. Purge logs are presented in Attachment A. Samples were placed on ice and transported under chain of custody to Argon Laboratories (DHS #1873) where they were analyzed for BTEX and TPHg using EPA methods 8020 and modified groundzclroeE3gm1996 F