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Attachment C:Field Investigation Procedures and Boring Logs affected soil and above groundwater, a soil sample was also collected from the unaffected interval to obtain vertical delineation. If no affected soil was observed in the boring, in addition to the HHSE sample one soil sample was collected just above the groundwater table 1. GROUNDWATER SAMPLING Grab groundwater samples were collected by placing a clean, pre-packed well screen or polyvinyl chloride (PVC)well screen into the borehole and collecting samples using a check valve with poly tubing. The well screen was inserted into the outer rods of the Geoprobe®Dual Tube sampling system, and a PVC riser was screwed into the well screen and plumbed to the ground surface. The dual-tube rods were retracted,with the well screen and PVC riser remaining in the borehole. After purging the well casing, groundwater samples were decanted into United States Environmental Protection Agency-approved laboratory-provided bottles, labeled, and placed in an ice-cooled chest pending analysis by Lancaster. SAMPLING LOCATIONS/SURVEY METHODS After completion, soil borings were geo-spatially located using a global positioning system (GPS) unit. (The GPS survey methods were consistent with SAIC FTP No. 175, "Field Measurement of Physical and Topographical Features.") EQUIPMENT DECONTAMINATION The decontamination of sampling equipment that did not directly contact the samples was performed in accordance with SAIC FTP No. 400, "Equipment Decontamination." Sample collection devices that directly contacted the samples were decontaminated in accordance with SAIC FTP No. 405, "Cleaning and Decontaminating Sample Containers and Sampling Equipment." In general, all non-dedicated equipment that came into contact with potentially contaminated soil or groundwater was decontamintated. Decontamination occurred prior to and after each use of a piece of equipment. For example,the down-hole equipment was cleaned between borings using a Liquinox""/water solution to prevent the possibility of cross contamination. The equipment was decontaminated in a predesignated area on plastic sheeting, and the clean equipment was stored in an uncontaminated area. Specific decontamination procedures for non-dedicated sampling equipment vary by sampler type, and they are more fully described in SAIC FTP No. 405. Disposable equipment intended for one-time use was not decontaminted, but was packaged for appropriate disposal. Reusable sampling equipment not coming into contact with potentially contaminated soil samples, but requiring decontamination, included field test meters;the water-level sounder; direct-push drilling rig cutting shoes, drive heads,piston asemblies, samplers, and other fittings; and stainless steel hand augers and trowels. Specific decontamination procedures employed for these types of sampling equipment are more fully described in SAIC FTP No. 400. 1. Geomatrix Consultants,Inc.,2005. Technical Approach to Site Evaluation and Decision-Making,Historical Pipeline Portfolio,Central Valley Region. February.