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< .. 0®r,100111 1 z w r SITE GEOLOGY AND HYDROLOGY The Sebastiani Vineyards/Woodbridge Cellars site is located on a broad, flat, alluvial plain at an elevation of approximately 20 feet above mean sea level (MSL). The site is located approximately 3 1/2 miles southwest of the Mokelumne River and is bordered qn three sides by vineyards and to the north by Turner School. A Western Pacific rail line runs northwest to southeast across the western side of the site. a Soils encountered during drilling and excavation activities at the site consisted of a slightly moist, clayey silt to silty sand unit to a depth of approximately eight feet below ground surface, underlain by a moist, silty, sandy clay that extended to an approximate depth of 17 feet. k saturated, moderately-well sorted, well rounded, fine grained sand to silty sand unit extended from 17 feet to 34 feet on the eastern side of the area of investigation. The bottom of this unit was encountered at increasingly shallower depths toward the west and was encountered at approximately 25 feet on the western side of the investigation area. A silty, slightly sandy, moist to very slightly moist clay unit was encountered beneath the silty sand in all"the monitor well borings drilled at the site. This unit was encountered at approximately 34 feet below ground surface in borings located on the east side of the investigation area and, as drilling activities progressed in a southwesterly direction, it was encountered at a depth averaging approximately 25 .feet. This clay unit extended to the total depth of all monitor wall borings. It's thickness was not determined., but it is at least 5 feet thick throughout the area explored. Generalized geologic cross sections which depict the lithologic units encountered at the site and a cross section reference map of the investigation ar-a are presented in Figures 4, 5, and 6. Groundwater level measurements were made at each monitor well on June 2, 1989, after a minimum 12-hour equilibration period following construction of monitor wells MW-9 and -10. A second sounding round was performed on June 19, 1989, allowing over two weeks for equilibration following well construction. The depth to water in each well was measured with an electric sounder. As shown in Table 3, groundwater surface elevations across the site varied by approximately 0,68 feet. The normal limit of accuracy for this method of measurement is 0.02 feet. A map of groundwater contours developed from the June 19, 1989, water level sounding measurements is shown on Figure 7. The contours suggest that groundwater at the site is moving in a southwesterly direction. ANALYTICAL RESULTS j As previously stated, analytical services for the site assessment work were provided by Weston Analytical Laboratory of Stockton, California and McLaren Analytical Laboratory of Rancho Cordova, California. These -laboratories- are-certified by-the-State- of- California, - Department-" of --..-;-- Health Services for hazardous waste testing. 13 IMMIMFawd