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3.0 Field Procedures This section describes the field.procedures to be used during Geoprobe soil sampling and field analytical testing. Standard operating procedures for the following activities will follow the approved Workplan for Supplemental Remedial Investigation at the Stockton MGP site(CH2M HILL, 199 1) and will not be repeated here: Work will be conducted according to the approved health and safety plan for the Stockton Former MGP site also included in the 1991 workplan. 3.1 Soil Borings and Soil Sampling A minimum of twenty-one soil borings will be drilled utilizing Geoprobe® equipment to a depth of approximately 25 feet bgs. The Geoprobe® equipment (Figure 3-1) consists of a mechanized vehicle mounted soil probe system which applies both static force and hydraulically powered percussion hammers for tool placement. The Geoprobe® uses a small diameter (1") probing tool which can be used for the recovery of soil vapor, soil core, and groundwater samples. During this investigation, the Geoprobe® will be used to collect a continuous soil core from each boring. The cores will be logged and based on the visual identification of chemicals, samples will be collected from the core for analysis. A boring log will be developed for each boring with all observations of oily, tary materials and discolored soils noted. Four samples will be collected from each boring for screening analysis. The depths of the samples will be at approximately 5 foot intervals to be determined based on field observations of where former MGP residues appear. All four samples from each of the 21 soil borings will be analyzed in the field using a field test kit. The field test kits will be used to analyze the samples for PNAs and petroleum hydrocarbons. The field test kit provides rapid onsite analyses for PNAs and aromatic compounds such as gasoline, diesel and BTEX. The procedure extracts the aromatic compounds from the sample and provides a colorimetric indication of the concentration and type of contaminants present. The color of the reacted extract solution indicates the type of compound, and the intensity of the color indicates the concentration. A portable GC will be used as a supplement to the field kits to better distinguish the PNAs from the petroleum hydrocarbons. During drilling of each soil boring, there will be a portion of the soil core which will not be sent for laboratory testing. This soil will be collected in 55 gallon drums and disposed of at an appropriate disposal facility upon completion of laboratory analyses. SFO10030BS3.DOC 3-1