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h <br /> (YVATC <br /> 1117 Lone Palm Avenue, Suite Modesto, CA 953511 <br /> www.atcassociates.com <br /> 209-579-2221 <br /> A S S O C I A T E S I N C Fax 209-579-2225 <br /> Environmental, Geotechnical and Materials Engineers <br /> allowed to recover and samples were collected from each well using disposable polyethylene <br /> bailers. <br /> I <br /> The groundwater samples collected from each well were submitted to SPL Laboratories <br /> (Environmental Laboratory Accreditation Program Certification No. 1142) located in Houston, <br /> Texas for chemical analyses of gasoline range organics (GRO) utilizing EPA Method 801513; and <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX), methyl tertiary butyl ether (MTBE), ethyl <br /> tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl <br /> ether (TBA), 1 ,2-dichloroethane (1 ,2-DCA), and 1 ,2-dibromoethane (EDB) utilizing EPA <br /> Method 826013 . Groundwater well purge and sample logs are included in Appendix D. <br /> 10 SUBSURFACE CONDITIONS <br /> 3_1 Geology <br /> Silt was encountered in the borehole of MW16 to approximately 9. 5 feet bgs and was underlain <br /> by silty sand to approximately 12 feet bgs.-Silt-Was encountered from approximately 12 to 17 feet <br /> bgs and was underlain by sands to approximately 27 feet bgs. Silt was encountered from <br /> 1 approximately 27 to 37 feet bgs and was underlain by clay to approximately 42 feet bgs, <br /> Alternating layers of silts and clay were encountered to the terminal depth of the boring at 60 feet '(li ..c <br /> bgs. <br /> I ,\, <br /> a �' <br /> L1 Silt was encountered in the borehole of MW17 td approximately 4 feet bgs and was underlain by <br /> clay to approximately 17 feet bgs. Silt was en untered from approximately 17 to 22 feet bgs and <br /> was underlain by clay to approximately 27 feet bgs. Silt was encountered from approximately 27 <br /> to 34 feet bgs and was underlain by sand to approximately 37 feet bgs. Clay was encountered t <br /> from approximately 37 to 59 feet bgs and was underlain by sand to the terminal depth of the <br /> boring at 60 feet bgs. <br /> As previously indicated_ in Section 2. 1 , the lithology previously logged for MW16 is assumed to <br /> be similar for MW 18 to approximately 60 feet bgs and generally consisted of alternating layers of <br /> 1 silt and sands to approximately 37 feet bgs. Alternating layers of clay and silts were encountered <br /> from approximately 37 to 62 feet bgs and were underlain by sand to approximately 77. 5 feet bgs. <br /> Clay was encountered from approximately 77. 5 to 81 . 5 feet bgs and was underlain by sand to <br /> approximately 84 feet bgs. Clay was encountered from approximately 84 to 87 feet bgs and wasVII <br /> underlain by sand to approximately 91 feet bgs. Clay was encountered to the terminal depth of <br /> i ( <br /> the boring at 92 feet bgs. � .r <br /> Silt was encountered in the borehole of MW19 to approximately 4 feet bgs and was underlain by , %,N Ili - k 9 1 c 1 <br /> clay to approximately 17 feet bgs. Silt was encountered from approximately 17 to 22 feet bgs and <br /> was underlain by clay to approximately 27 feet bgs. Silt was encountered from approximately 27 t t <br /> to 42 feet bgs and was underlain by clay to approximately 56 feet bgs. Sand was encountered 'J` t) <br /> (�us1�`""� 4 4 <br /> — , t <br /> S:\Enviromental\28349\reports\Inv rpt 2008.doc 5 ATC Associates hie, e,, <br /> r� 't <br /> i <br /> — I <br />