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well casing to calculate the groundwater elevation These data are summarized in <br /> Table 5, and graphically shown on the Groundwater Elevation Map (Exhibit 4) The <br /> resulting map indicates groundwater elevations decrease to a southeasterly direction, <br /> at a gradient of 0 021 feet/foot Consequently, the flow is in the direction of the <br /> Stanislaus River, assuming groundwater flows perpendicular to the mapped contours <br /> The Stanislaus River flows ,n a southwesterly direction and lies approximately 1 mile <br /> southeast of the site The gradient observed beneath the site places MW-2 in an <br /> upgradient position, and MW-1 and 3 in a lateral position with respect to the former <br /> tank cluster <br /> The groundwater gradient observed at the site is not in accordance with published <br /> data Regional groundwater maps (State of California, Dept of Water Resources- San <br /> Joaquin District, 1989, Spring 1988 unconfined groundwater maps) show the <br /> unconfined aquifer in the vicinity of Ripon decreases in elevation in a westerly and <br /> southwesterly direction The discrepancy in gradient direction between regional and <br /> site groundwater maps may be the result of the saes proximity to the Stanislaus River <br /> or from seasonal changes <br /> f r t hry TABLE 5 a.fr r i Vr r „r rrr <br /> SUMMARY OF GROUNDWATER ELEVATIONS(ft) <br /> Elevation , Depth Groundwater Elev <br /> • Borin Date Top of Casino to Groundwater Ref to Bench mark <br /> MW-1 8/25/93 99 19 29 46 69 73 <br /> MW-2 8125193 99 70 29 35 70 35 <br /> MW-3 8/25193 98 80 29 15 69 65 <br /> S it w S ♦ .. w { ` r r ry <br /> 8 0 CONCLUSIONS <br /> The primary source of hydrocarbon fuel release has been eliminated by the removal of <br /> the former underground fuel storage tanks <br /> Laboratory analysis of selected soil samples indicate the highest concentrations of <br /> hydrocarbons impacting soil hes within the vicinity of boring TH-1 , located on the <br /> eastern side of the former tank cluster <br /> Laboratory analyses of soil samples from Boring TH-1 indicate the vertical profile of <br /> impacted soil extends from below the former excavation at a depth of approximately 10 <br /> feet (bsg) to groundwater at a depth of approximately 29 feet (bsg) <br /> ., 15 of 17 <br />