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C Ms.Lori Duncan <br /> A M B R I A <br /> November 18,2005 <br /> unidentified peaks not matching a typical fuel pattern. Benzene was detected in wells MW-4, <br /> MW-6 through MW-10, and VEW-2 from 0.59 to 2,300 ppb. MTBE was detected in wells <br /> MW-2, MW-4, MW-8, and MW-12 from 2.3 to 22 ppb. Wells MW-7 and MW-8 contained <br /> 7.2 and 14 ppb tertiary butyl alcohol (TBA), respectively, and well MW-11 contained 32 ppb <br /> DIPE. 1,2-dichloroethane (1,2-DCA) was detected in wells MW-12 and MW-13 at <br /> concentrations of 67 and 0.57 ppb,respectively. <br /> Cambria presents well and boring construction data in Table 2, historical soil data in Table 3, <br /> historical groundwater investigation analytical data in Table 4, and historical groundwater <br /> monitoring data as Attachment A. <br /> © Site Geology <br /> The site is located within the Great Valley geomorphic province. The Great Valley is a northwest <br /> trending structural trough, which borders the Sierra Nevada to the east and the Coast Ranges to <br /> the west. It is underlain by a thick sequence of sedimentary units, including Quaternary alluvial <br /> deposits. <br /> Subsurface soils beneath the site consist of both fine-grained soils (clays and silts) and coarse- <br /> grained soils (sands and silty sands)of varying thicknesses to the total explored depth of 100 fbg. <br /> Boring logs and cross sections are provided as Attachment B. <br /> Hydrogeology <br /> Current depth to water in the site wells ranges from approximately 37 to 39 fbg. Initially, when <br /> groundwater monitoring began in 1990,groundwater was nearly as deep as 60 fbg. Groundwater <br /> rose until the years 2000 and 2001, when groundwater depths were approximately 31 fbg. Since <br /> then, groundwater depths have dropped to current levels. Groundwater flow is consistently <br /> towards the east. The groundwater gradient is relatively flat, typically ranging from 0.002 to <br /> 0.004 ft/ft. Figure 3 depicts groundwater contours and flow direction based on third quarter 2005 <br /> groundwater monitoring data. <br /> DPE WELL INSTALLATION WORK PLAN <br /> There are currently two DPE and/or SVE wells on site (VEW-1 and VEW-2). To effectively <br /> remediate the presumed source area near the former USTs, additional DPE wells are warranted. <br /> These wells are proposed below. <br /> 5 <br />