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October 1.3, 2988 AGS Jab No. 86102--3 i Page 2 The borings were drilled through 10-inch-diameter polyvinyl chloride (PVC) conductor casings which were set in the tank cavity down to the center of the product tanks. The conductor casings were installed when the upper portion of the pea gravel backfill was replaced, and were secured in sheet-metal utility boxes with steel lids and watertight seals. Soil boring B-6 was drilled to a total depth of 16 feet; borings B-7, B-8, and B-9 were each drilled to a total depth of 15 feet. During drilling, soil samples were collected at 5-foot intervals using a California-modified split-spoon sampler equipped with clean brass ` sleeves. Samples were collected by advancing the boring to a point immediately above the sampling depth and then driving the sampler into the undisturbed native soil throughthe hollow stem of the auger. The tank ca-Aty backfill was not sampled. The sampler was driven 18 .inches with a standard 140-pound hammer dropped 30 inches. The number of blows roquired to drive the sampler each successive 6-inch interval was counted and recorded to give an indication of soil consistency. Samples were identified using the Unified Soil Classification System (Plate P-3) . A portable organic vapor analyzer (OVA) was .used in the field to semi-quantitatively evaluate contamination of each sample. Descriptions of the earth materials encountered are ? presented in the Logs of Borings, Plates P-4 through P-7. E Samples collected for possible laboratory analyses were removed from the sampler and sealed with aluminum foil, plastic caps, and s airtight tape. They were then labeled and placed in iced storage for transport to the analytical laboratory. A Chain of Custody Record was initiated by the sampler and accompanied the samples to the laboratory. A copy of that record is attached to this letter. Vapor-recovery wells VW-4 through VW-7 were constructed in soil borings B-6 through B 9, respectively, using thread-jointed, 2-inch-inner-diameter, schedule 40 PVC casing. No chemical cements, glues, or solvents were used in well construction. The screened portions ct the wells consist of factory-perforated casing with 0.020-inch-wide slots. In each well the screened portion _extends from_total_depth-_to.a-_point-approximately_8_.-5 ". feet.below grade. The annular snac� o -- pposite- the screen was . . -, - - packed with sorted..sand' to a point-2 to 3 feet above the ton of a the screen. A .1- to 2-foot--thick a ntonite seal wasp laced above , the :sand to prevent cement from entering the sand pack. The remdining.annulus was backfilled 3ith neat cement to grade. The wall heads were secured with the previously installed utility tt boxes. ,4PPIled GeOSYStems