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All analysis were performed on a laboratory grade Hewlett Packard model 5890 Series 11 gas chrorriatograph equipped with a Flame Ionization Detector (FID). A -- Restec F T-5 (15 meter by 0.53 micron) wide bore capillary column using nitrogen as the carrier gas was used to perform all analysis. All results were collected on a 80386 based personal computer utilizing Hewlett Packards PC - based chromatographic data collection and handling system. Quality Assurance The gas chromatograph was calibrated on a daily basis by preparing a 1.0 ng/ul gasoline solution in a 40ml air tight EPA vial from neat gasoline. A three point calibration consisting of 20, 50 and 100 ng injections were performed at the beginning of each day. A calibration factor based on a best fit line through these points was calculated using the HP data system. If the r2 factor generated from this line was not greater than 0.980, an additional three point calibration is performed. The calibrations curves for this project are included with this letter. Detection limits were calculated from this calibration to be 0.07 ng/ml. Concentrations reported for benzene, toluene and total xylenes are relative to the 50 ng gasoline standard and calculated by using the the relative percent of each compound versus the total In addition to the three point calibration, an additional mid-point continuing calibration- and duplicate analysis were performed after the tenth sample each day. This information is given in the Soil Gas Quality Assurance Table along with the results of all blanks. w: Subsurface Conditions Observations made during probe emplacement and removal showed soil types to be a hard, low plasticity brown clay. Near the tank, this clay showed greater moisture content than others areas. The depth of this clay is estimated to be at least 10 feet below ground surface based on the two 13 foot samples collected. �. These clays offered significant resistance to air flow, indicating that their effective porosity is low to negligible. Scope of Work To achieve the objectives of this study, a total of 22 soil gas points were tested for Total Volatile Petroleum Hydrocarbons (NPH) with BTX distinction. Sampling ` locations are given on Diagram 1. Of the 22 points, 2 points, SG-3 and SG-12 were tested at multiple depths (5 and 13 feet). Two samples were also analyzed at point SG-3 at 5 feet in an attempt to see if a shorter purging time would assist in the results. Three samples were collected at point SG-16 due to unusually_high_readings--in_the-_first_two_samples_collected--at.this probe was placed and the results came back very low (1.3 ng/ml). No odor was observed in the soil or from the pump indicating that the lower reading is OTI.9D0501 2 _