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w <br /> STANDARD OPERATING PROCEDURES FOR DRILLING AND SOIL SAMPLING <br /> Standard operating procedures (SOPs) used by The Twining Laboratories, Inc. (Twining) <br /> when drilling soil borings, and sampling soil are presented below. Twining observes these <br /> procedures in order to obtain consistent, reliable data. <br /> Subsurface assessment permits will be filed with the appropriate regulatory agencies prior <br /> to conducting field operations. Field activities will be performed under the direction of a <br /> California-registered geologist. <br /> Soil borings will be drilled using an appropriate method. The method selected will depend <br /> upon project objectives and subsurface conditions. <br /> Drilling and sampling equipment will be thoroughly cleaned before, during and after each <br /> use. Cleaning procedures are described in Twining's "Standard Operating Procedures for <br /> Equipment Decontamination". <br /> Soil samples will be collected using a continuous-coring device, by driving a split-spoon <br /> sampler, or by grabbing samples from the drilling cutting returns. The sampler or coring <br /> device will be lined with brass, stainless steel, or acrylic tubes, in which samples may be <br /> retained for subsequent chemical analyses. <br /> Soil samples will be examined for the purpose of preparing lithologic logs, and screened for <br /> evidence of volatile organic chemicals (VOCs) using a photoionization detector (PID) or <br /> Drager tube. If a PID is used, it will be calibrated daily according to manufacturer's <br /> recommendations. <br /> Screening for VOCs is performed by placing samples in sealed glass containers, and placing <br /> the containers in a warm atmosphere for approximately 15 minutes to allow volatiles to <br /> escape from the soil. The PID probe or tip of the Drager tube is inserted into the container <br /> to measure VOC concentration in the sample head-space. The greatest concentration of <br /> organic vapors or the drager tube reading will be recorded on the soil boring log. <br /> Generally, two soil samples from each soil boring will be submitted for chemical analyses. <br /> Soil samples selected for analyses typically represent the greatest head-space analysis <br /> reading recorded for each soil boring, and the sample from just above first-encountered <br /> groundwater. Samples intended for chemical analyses will be sealed with Teflon tape and <br /> plastic end caps, labeled, placed on ice, and delivered to a laboratory, along with chain-of- <br /> custody documentation. <br />