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Extender!Site Characterization Report• 7500 West Eleventh Street, Tracy, CA. Page 26 NPbeen located. However, from the perspective of site characterization and planning for site . y remediation, it is clear that groundwater flows to the north from the area to the rear of the Casa Mendoza restaurant, north beneath West Eleventh Street and continues in a <' direction that is generally somewhat east of north in the direction of the intersection of Carmelo Avenue and Chrisman Road. { 6.3 Hydrostratigraphy As was noted earlier, the soils beneath the 7500 West Eleventh Street property and adjacent areas are composed of clays, silty and sandy clays, silt and sands that are complexly interbedded. Boring logs prepared when the push-probe borings and the borings for the groundwater-quality monitoring wells described in Sections 4.0 and 5.0 were drilled enabled details of this complex system to be developed. Figures 9, 10 and 11 are hydrostratigraphic sections along the lines A-A', B-B' and C-C' shown on Figure 8. The hydrostratigraphy shown in the cross sections is an interpretation of the stratigraphic data from the boring logs that divides the sediments into two classes; =' the permeable sands and silts and the relatively less permeable clays and silty clays. That presentation makes it possible to reduce the details of the stratigraphy to a tractable degree of complexity by distinguishing between the different soil types based on the =� properties that are of importance to the understanding of the distribution and transport of i fuel hydrocarbons in the subsurface. From the ground surface to depths varying between 1 ft. and, locally, up to 7.5 ft., the whole of the site is overlain by fill material consisting of sands, gravels, concrete debris, highway paving and base course materials, together with disturbed and remolded native soils. Beneath the fill material to a depth of some 11-15 ft. beneath the ground surface is -:= a layer of relatively impermeable clays and silty clays, the upper 5-10 ft. of which are dark gray in color, while the deeper of those clays are typically light brown. Below those clays is the top of a zone of the subsurface consisting of sands and silts that have a lenticular structure, with varying degrees of interconnectivity between the lenses of those materials. That zone extends to depths varying between approximately 11 and 24 ft. Below this are other light brown clays and silty clays that appear to be arealy continuous beneath the areas of the property and adjacent land that were explored. When the sands described above were encountered in borings, they were generally composed of --� fine to medium-course, sub-rounded particles with some silt. They are, locally, very loose. i As is shown on Figure 9, the sand stratum beneath the near-surface clays appears to be present along the length of Section A-A', which starts south of the Casa Mendoza restaurant and continues from there through the area of the site where the dispenser islands were Iocated, then across West Eleventh Street and northward to at least the area around the intersection of Carmelo Avenue and Chrisman Road (see Figure 8 for locations). It is recognized that this stratum may not, in fact, have the degree of continuity that is shown by the interpretation presented on Figure 9. However, a reasonable sic