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a • <br /> March 8, 1999 <br /> • Page 2 <br />. SCOPE OF WORK <br /> Field and laboratory procedures are presented as Attachment A The specific scope of <br /> work is discussed below <br /> Permits. IT obtained the appropriate groundwater monitoring well permits from the San <br /> Joaquin County Public Health Services Environmental Health Division prior to initiating <br /> fieldwork <br /> Soil Boring and Groundwater Monitoring Well Installation. IT drilled and installed <br /> three wells (MW-I through MW-3) between September 22 and September 25, 1998 at the <br /> approximate locations shown on Figure 2 The monitoring wells were installed to <br /> determine groundwater flow direction and gradient and to assess dissolved hydrocarbon <br /> concentrations in groundwater on site Field procedures are described in Attachment A <br /> Boring logs are presented as Attachment B <br /> Soil Sampling and Analysis. Soil samples from Well MW-1 were collected from a <br /> continuous core boring segmented in five-foot depth intervals Soil samples collected <br /> from Wells MW-2 and MW-3 were collected in five-foot intervals using a California <br /> modified split-spoon sampler Soil samples were submitted to a California State-certified <br /> laboratory and selected samples were analyzed for the presence of total petroleum <br /> hydrocarbons quantified as gasoline (TPH-g), benzene, toluene, ethyl benzene, total <br /> xylenes (BTEX), and oxygenates including methyl tert-butyl ether (MtBE) Field and <br />• laboratory procedures are presented in Attachment A <br /> Monitoring Well Development and Surveying. The wells were developed and sampled <br /> by Blaine Tech Services during regular quarterly monitoring activities starting fourth <br /> quarter of 1998 The results of Blaine Tech's fourth quarter 1998 monitoring event are <br /> presented in Figure 3 and are incorporated in the discussion of findings below A <br /> California State-certified surveyor surveyed the new wells for location and elevation <br /> relative to mean sea level (MSL) Field and laboratory procedures are presented in <br /> Attachment A Surveyor's map and data are presented as Attachment C <br /> FINDINGS <br /> Subsurface Soil Conditions <br /> Soil encountered in the northern area of the site during drilling consisted primarily of <br /> silty sand and sandy silt to the maximum depth explored (approximately 91-1/2 feet bgs) <br /> Subsurface material encountered in the southern area of the site consisted of sandy clay <br /> from 2 to 28 feet bgs This clay layer was underlain by silty sand and sandy silt to a <br /> maximum explored depth of 76-112 feet bgs Detailed descriptions of the subsurface <br /> materials encountered are included in the boring logs presented in Attachment B <br /> i <br /> 920-122 IC/REPORT <br />