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i was moved southerly to make room for present activity. The two tank excavations had a center, berm area between them; this area was removed first, it being between the tank locations and where contamination had been found. L The materials removed were as follows : About 6" of concrete where -it had not been previously removed, then 3 ' to 4 ' of black, organic clay, slightly thicker at the north end of the excavation. This clay, identified herein as the "Stockton Adobe Clay" , dried from a totally black color to a somewhat lighter, dark grey. Then a tan to reddish brown, silty clay that varied somewhat as to clay content with depth,; becoming more dense with a higher clay content just a few feet below the Adobe clay. Hydrocarbon odors and staining were easily identified both in the Adobe and the I I tan to reddish clay below. There were some streaks of bluish clay mixed with the reddish clay and one streak of fine, fluffy., dry silt on the west wall at about 12 ' bgl . The reddish color turned to a brownish tan upon drying. i As a general statement, no odors or staining were observed below about 201 . Samples were taken on bottom at 201 , and in several locations at shallower depths, to check for .both depth .-and lateral extent of possible contamination, sample #' s 1 through 5 . 1 The black Adobe appeared to have acted as a conduit for flow C of the contaminants; consequently, the excavation was extended laterally farther at shallow depths . This can be f E seen on Figure 6 . Although the depth contours of the a excavation are approximate, they show the shelf made by extending the excavation laterally in the Adobe clay . q At about 3 : 30 PM, while digging on the east side of the f excavation what at first appeared to be a seam of oily sand ` was found just above the Adobe . Examination and discussion with Roger Scriven and Richard Thorpe proved this to be i degraded (dissolved) asphalt lying just below a partition in the overlying cement. The expansion joint in the cement had allowed hydrocarbon product to seep into an asphalt base for the cement pad, and essentially dissolved it. The lateral extent was limited to the area just below the expansion , joint.' Linda Turkette, EHD, arrived on site while this was M J. being discussed. x i At this time, the last two samples, # ' s 6 and 7, were taken 4 at the pit bottom of about 20 ' . The deepest hydrocarbon odors that were noticeable were at about 18 ' bgl . `- The pit dimensions were measured at several locations and these measurements are reflected in Figure 6 . Figures 7 and 8 are cross sections of the pit, showing scale and lithology. These sections, and Figure 6, the plan view, are approximately to scale; however, they are idealized and do 4 l �