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1. H:KLEINFELDER &:ASSOCIATES ? F r or, untilu _Burface .s.tructures:. prevented,ftwther advancement. The locations � of the soil bor _ ons i borings and the radial lines are shown on Plate 2. 3;2 SAMPLING PROCED A` 'truck`mounted drillrig equipped with 6-1.nch boll ow stem augers was used to Breach the desired sampling p nS depths. Soil samples were collected by advancing ,=a. soil. boring .to a point immediately above the desired sampling depth and then driving ' a Modified California Sampler lined with three brass tubes into the undisturbed soil. The sampler was then removed from f the bottom of the bora ' ng and the bottom (third) tube sealed with aluminum foil and tight fitting plastic caps, labeled and placed inside an iced s cooler. At the end of drilling operations, select soil samples were delivered under chain-of-custody to California Analytical Laboratory/ Enseco in West Sacramento. The remaining soil samples were retained in refrigerated storage for future reference or analysis. To minimize the �! ^ potential for cross-contamination between soil borings, all augers and associated equipment were steam cleaned prior to the , drilling of each soil boring. The sam li 'I P ng equipment was cleaned with a trisodium phosphate wash and a distilled water rinse prior to the collection of each soil sample. During the sample collection an experienced environmental geologist classified the subsurface soils and logged the boreholes. Descriptions of - the soil encountered in 'each soil boring, and identification of the sample depth and soil t _._- .�..�__._..aw type are presented on the Log of Borings, :Plates 19 through 33. A copy of the Unified Solis Classification System (used to identify the soil) is included as Plate 18. j 3.3 QUALITATIVE LD SCREENING To provide a qualitative ication of contamination a .4 portable organic vapor detection instrument was tilized in the investigation. The ;1 instrument is a Photovac TIP utilizi 10.6 eV photoionization lamp. A 25 ppm benzene calibration gas was select and used to set a reference 38-87-51 A..