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• The total depth of each soil boring was approximately two to five feet below the estimated <br /> bottom of potential subsurface contamination. If field monitoring and observations indicated <br /> contamination, borings were extended beyond the proposed total depth. Soil samples were <br /> collected in decontaminated brass tubes or dedicated polyethylene liners. The Versar Site <br /> supervisor ensured that the sampling equipment was thoroughly cleaned prior to collecting each <br /> sample. Samples were collected, placed in containers, preserved, and analyzed within the time <br /> constraints of applicable local, state, and federal procedures. Upon collection, each sample was <br /> labeled with a unique sample identification number, sampler's initials, date, and time, listed on <br /> the chain of custody, and then placed in a cooler with ice. Custody of the samples began at the <br /> time of sample collection and was maintained by the sampling team supervisor until the samples <br /> were relinquished to the laboratory. Laboratory analyses were performed by a California <br /> Department of Health Services-certified laboratory. <br /> At soil vapor sample target depths, the coring tube was withdrawn and replaced by a vapor <br /> sampling probe. The probe was driven into undisturbed soil and a sample drawn through <br /> polyethylene tubing. After purging a minimum of three volumes of air, a sample was collected <br /> from the sample tubing in a stainless steel and glass syringe for on-site analysis by a mobile <br /> laboratory. Air line tubing was discarded after each use. Chain-of-custody procedures were <br /> maintained from the field to the on-site laboratory. A number of samples were collected using a <br /> laboratory-prepared Summa® canister instead of a syringe. These samples were delivered to a <br /> fixed-base laboratory with chain-of-custody documentation for analysis. Field analysis of the <br /> purge air was used to guide soil sampling for laboratory analysis. Quality control soil vapor <br /> • samples were collected using the Summa canister. The filled Summa canister was delivered to a <br /> fixed-base laboratory with chain-of-custody documentation for analysis. <br /> Soil samples were selected for analysis according to the chemical of concern in each area. Soil <br /> gas samples were analyzed for VOCs in the field using a California EPA-certified mobile <br /> laboratory. Soil vapor samples were analyzed for VOCs, including BTEX and MTBE, using <br /> EPA Method 8260B. Approximately 10 percent of the soil gas samples (selected as samples of <br /> concern based on field analyses) were submitted to an offsite laboratory and analyzed for VOCs, <br /> including BTEX, using EPA Method TO-14. <br /> 3.2.3 Boring Abandonment <br /> Following the completion of all sampling activities, each of the direct push and hand-auger <br /> sampling locations was backfilled with cement containing up to five percent prehydrated <br /> bentonite. <br /> 3.3 Groundwater Evaluation <br /> Groundwater was not encountered during the field investigation. To evaluate the current <br /> groundwater quality around the former jet fuel UST s at the AASF, Versar purged and sampled <br /> the three existing groundwater monitoring wells during the Site investigation activities. Each <br /> • monitoring well was purged of approximately three casing volumes of water, the water level <br /> 2187-01/3134-100/MAY26'00 8 <br />