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F <br /> • 07 March 2003 <br /> AGE-NC Project No 95-0141 <br /> Page 5 of 10 <br /> 2 4 2 Ground Water Sample Collection and Analysis -- <br /> I Pnor to the collection of ground water samples,the depth to ground water was re-measured in each <br /> well to ensure that a mimmum of 80% of the initial water volume had recharged A water sample <br /> was then collected from each well using a new, dedicated, disposable plastic bailer Immediately <br /> upon retrieval, the sample was transferred into three properly labeled 40-ml EPA-approved VOA <br /> vials containing 0 5 ml 18% hydrochloric acid as a sample preservative The samples were logged <br /> on a chain-of-custody form, stored in a chilled container and transported under chain-of-custody to <br /> IMAI, The ground water samples were analyzed for <br /> • TPH-g in accordance with EPA Method 8015 Modified, <br />' • BTEX in accordance with EPA Method 8260B, and <br /> DIPE, ETBE, MTBE, TAME, TBA, EDB, 1,2-DCA, ethanol and methanol in accordance <br /> with EPA Method 8260E <br />� . 25 WELL HEAD SURVEY <br /> On 22 November 2002,a California state-licensed survey engineer from Baumbach and Piazza,Inc <br /> I surveyed a reference point on the top of wells MW-3, MW-6, MW-7, MW-8A/B through <br /> MW-12AB and EX-1 to the nearest 0 01-foot relative to City of Stockton Bench Mark#HS 4491, <br /> at 7 70 feet above mean sea level (MSL) The results of the monitoring well survey are contained in <br /> Table 1 The surveying report (Baumbach and Piazza, Inc ) is presented in Appendix F <br /> I3.0. FINDINGS <br /> Soil stratigraphy and hydrostratigraphy were determined from field data collected on 10 October <br /> I 2002,supplemented with boring logs recorded during installation of ground water monitoring wells <br /> MW-1 through MW-4, MW-6, MW-7 and MW-9 Ground water elevation, flow direction, and <br /> gradient were determined from field data collected on 28 October 2002 The contaminant impact to <br /> I soil and ground water was assessed from the laboratory analytical data collected on 10 and <br /> 28 October 2002 <br /> I31 STRATIGRAPHY <br /> Generally, sand, silty sand and gravelly sand were encountered at depths between approximately <br /> 20 and 31 feet bsg,48 and 74 feet bsg and 113 and 117 feet bsg Silt, silty clay,clayey silt, sandy silt <br /> and clay were observed at all other depths Cross sections A-A' and B-B' depict general lithology <br /> I <br /> Advanced GeoEnviranmental,Inc <br /> I <br />