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TO E RO E K SOP No.004,REv.2 AssoclATEs,INC SOIL SAMPLING I PAGE 4 samples, using the Unified Soil Classification System (USCS), should be recorded. Field tests such as head space analyses can also be conducted. Soil samples for chemical analyses can be collected either as grab samples or composite samples. A grab sample is collected from a discrete location or depth. A composite sample consists of soil combined from more than one discrete location. Typically, composite samples consist of soil obtained from several locations and homogenized in a stainless steel or Teflon® pan, tray, or baggie. Refer to the site-specific FSP or QAPP for methodology for composite sample collection. Samples for volatile organics analysis should not be composited. All soil samples collected should be packaged and shipped to the laboratories in accordance with SOP 015. All non-dedicated or non-disposable equipment used for soil sampling should be decontaminated between sampling locations in accordance with SOP 002. 2.1 SOIL SAMPLE COLLECTION PROCEDURES Soil samples can be collected as discrete samples for volatile organic compound (VOC) analysis using specialized equipment for preservation in the laboratory or in the field. Soil samples collected for non-VOC analysis can be collected as either grab or composite samples using standard equipment. 2.1.1 Procedure for Preserving and Collecting Soil Samples for VOC Analysis Samples collected for VOC analysis using traditional methods, such as collection in a jar with no preservation, are shown to yield non-representative samples due to loss of VOC's. To prevent such losses preservation with methanol or sodium bisulfite may be used to minimize volatilization and biodegradation. This preservation may be performed in the laboratory or in the field, depending on the sample collection methodology used. The specific sampling methodology will be specified in the project- specific QAPP or work plan. Soil samples to be preserved in the laboratory are collected using SW-846 Method 5035. For samples preserved in the field, laboratories may perform low-level analysis (sodium bisulfate preservation) or high- to medium-level analyses (methanol preservation), depending on the project-specific QAPP.