ARCHIVED REPORTS XR0001740 - Laserfiche WebLink

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August 3 , 1988 AGS Job No. 86091-6 Page 2 was performed under the guidance of a geologist registered by the State of California, who logged the earth materialsrin the borings as drilling proceeded. Soil borings B-6 and B-9 were drilled in the tank cavity through 10-inch-diameter, polyvinyl chloride (PVC) conductor casing set in pea gravel used as backfill when the central underground storage tank was replaced. soil borings B-7 and B-8 were drilled through native soil on the north and east sides of the tank cavity. Barings B-6, B-7, and B-8 were each drilled to total depths of 41.5 feet; boring B-9 was drilled to a depth of 42 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 through the hollow stem of the auger. The sampler was driven 18 inches with a standard 140-pound hammer dropped 30 inches. The number of blows required 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 semiquantitatively Evaluate contaminant concentrations of each sample. Descriptions of the earth materials encountered are presented in the Logs of Borings, Plates P-4 through P-11. Ground water was not encountered during drilling of the soil borings. Samples selected for laboratory analysis were removed from the sampler and sealed with aluminum foil, plastic caps, and 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 . ield geologist and accompanied the samples to the analytical laboratory, A copy of that record is attached to this letter report. Vapor-recovery wells VW-6 through VW-9 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 of the wells consist of factory-perforated casing with 4. 020-inch-wide slots. In .each well, the screened portion extends from the total depth of the boxing to a point approximately 11.5 feet below the existing grade. The annular space opposite the screen was packed with sorted sand to a point