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construction of MW-DIS-8D, which extended to 142 feet, show evidence of a laterally extensive sand unit first encountered at approximately 120 feet. This sand unit is referred to herein as the B Zone. It is assumed that the clay that separates the A from-the B Zone is 'discontinuous, and that the A and B Zones are hydraulically connected. Information related to stratigraphy at depths below 140 feet comes from drilling logs made during construction of Del Monte's production wells. Between 150 and 200 feet, records show interbedded material. At 200 feet, a sand and gravel zone was encountered that extends to 500 or 600 feet where blue clay was observed. Cross sections A-A and B-B presented in Figures 3-8 and 3-9 show an interpretation of the ti subsurface stratigraphy. Typical of alluvial sediments, individual stratigraphc units are not I laterally extensive. Cross section A-A shows a series of isolated, stacked clay and silt units that cannot be correlated across the site. Section B-B indicates that there is a slightly higher degree of stratigraphic continuity in the northwest-southeast direction. The higher degree of j lateral continuity in the direction of B-B may reflect that the sediments were originally deposited along this southeast to northwest trend. j Local Hydrology First-encountered water in soil borings occurs at approximately 70 feet bgs (elevation -50 feet NGVD). Naturally occurring fractures in the clay at this depth exhibited free water along the fractured surfaces."However, this zone would not readily transmit water to the borehole. Each borehole and monitoring well was extended below 70 feet to a more permeable sand ? layer before Hydropunch groundwater samples were collected. Historically, groundwater elevation has fluctuated from a low of-80 feet NGVD in the mid- 1970s to a high of-32 in the mid-1980s, as shown in Figure 3-10. Groundwater elevation was approximately -47 feet in March 1995. Quarterly Groundwater Monitoring j Shallow Groundwater Gradient Water levels were measured at the site on March 2 and 3, 1995, by Del-Tech. A summary of these depth measurements and the elevations is provided in Table 3-2. The depths .were converted to elevations and are presented on Figure 3-11 as groundwater contours of the A Zone. If the mounding created by the AS/SVE system operation is removed from consideration, a rough estimate of the shallow gradient is 0,001 Edit. The shallow gradient has historically been flat, and the direction of flow has been highly variable. A Zone groundwater presently flows to the southeast. Previous quarterly monitoring results collected from fall 1991 to winter 1994 show a groundwater surface gradient in the northwesterly direction. The change in groundwater flow direction could be driven by temporary surface infiltration or the discontinuation of production well pumping by Del Monte since summer 1994. Additional f ' SPO10030982.DOC 3-15