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GROUND ZERO ANALYSIS, INC. VIED <br /> 1714 Main Street 2005 <br /> Escalon,California 95320-1927 ENVIPiONMEN1 HE4TH <br /> Telephone (209)838-9888 PL_ <br /> Facsimile <br /> �/ �����S <br /> Facsimile (209)838-9883 <br /> April 6, 2005 <br /> Mr Harlin Knoll <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, CA 95202 <br /> Subject First Quarter 2005 Groundwater Monitoring Report <br /> 7835 Thornton Road, Stockton, CA (APN#077-490-27) <br /> Dear Mr Knoll <br /> This report summarizes activities at the subject site during the first quarter 2005 The site location is <br /> presented on Figure 1 Activities conducted during the reporting period included monitoring depth to <br /> water in site wells, purging and sampling wells MW2 and MW5, and analyzing groundwater samples for <br /> benzene, toluene, ethylbenzene, total xylenes (BTEX), and total petroleum hydrocarbons as gasoline <br /> (TPHg) <br /> GROUNDWATER MONITORING AND SAMPLING <br /> An experienced Ground Zero technician measured the depth to groundwater in wells MWi, MW2, MW3, <br /> MW4, MW5, and MW9 on February 17, 2005 The depth to groundwater beneath the site ranged from <br /> 35 44 feet below the top of the well casing (btoc) in well MW3 to 37 14 feet btoc in well MW2 <br /> Groundwater elevations in site wells rose an average of 3 06 feet between November 24, 2004 and <br /> February 17, 2005 The water table beneath the site lies above the screened intervals in wells MW4 and <br /> MW5 Groundwater flow was generally toward the east-northeast with an average gradient of 0 002 feet <br /> per foot (approximately 11 feet per mile) A potentiometric surface map for February 17, 2005 is <br /> presented on Figure 2 Monitoring well construction details are summarized in Table 1 Groundwater <br /> monitoring data is summarized in Table 2 <br /> A Ground Zero technician purged at least three well casing volumes of groundwater from monitoring wells <br /> MW2 and MW5 on February 17, 2005 Physical parameters (temperature, specific conductance, and pH) <br /> were measured and recorded during the purging process Groundwater samples were collected using a <br /> dedicated disposable bailer after physical parameters stabilized and the water level recovered to the pre- <br /> purged levels The samples were decanted into 40-m1 glass vials preserved with a hydrochloric acid <br /> solution The samples were subsequently placed in an ice chest refrigerated to a temperature of <br /> approximately 4°C <br /> The samples were transported to Argon Laboratories (ELAP 92359) under chain of custody protocol and <br /> analyzed for TPHg and BTEX utilizing EPA methods 8015B and 8021B, respectively Purged <br /> groundwater was contained in a labeled 55-gallon drum pending disposal Copies of field purge logs and <br /> water level measurements are included in Attachment A <br /> G 1GROUNDZE\KNOWLES HAM\R£P0RTSIQMR1200511QM2005 doc <br /> 7 <br />