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a. ♦� kn KLEINFELDER <br /> cleaned with a trisodium phosphate wash and distilled water rinse prior to the collection of <br /> each soil sample. <br /> Because it appears that ground water is approximately 10 to 12 feet below ground surface, <br /> soil contamination may not be laterally extensive. Therefore, the soil-gas survey and initial <br /> Lr three borings may be sufficient to assess the extent of the soil contamination. <br /> 3.3 QUALITATIVE FIELD SCREENING <br /> +.- A Photovac TIP using a photoionization detector (PID) will be used to screen each soil <br /> sample collected from the borings. The PID field screening of the soil samples can provide <br /> a qualitative indication of the presence of petroleum hydrocarbons. The PID measures <br /> total ionizable compounds in air in parts per million by volume (ppmv) in relation of a <br /> select calibration standard. Selection of samples to be submitted for chemical analysis will y� <br /> be based on visual observations and PID screening results. <br /> 3.4 MONITORING WELL CONSTRUCTION <br /> +— Three monitoring wells will be installed at locations based on the soil-gas survey results. <br /> One of these wells will be installed in the estimated, or apparent, upgradient direction to <br /> assess background levels of hydrocarbons in the ground water. Based on regional water <br /> flow patterns, is it anticipated that this well will be west-southwest of the tank excavation. <br /> The other two wells will be installed downgradient, at or near the edge of apparent <br /> contamination based on the findings of the soil-gas survey. Estimated well locations are <br /> shown on Plate 3. These locations may be revised, based on the results of the soil gas <br /> survey. <br /> ` The wells will be installed in borings drilled with an 8-inch hollow stem auger, to r��,,� <br /> approximate depths of 25 feet. Soil samples will be collected at 5-foot intervals during ��4r <br /> ��/ <br /> *� drilling for visual observation, field screening, and lithologic logging. �5 <br /> Construction details for the wells will be as follows: � 5 <br /> o The well casing will be 2-inch-inside-diameter, flush-threaded joint, schedule <br /> 40 PVC pipe. <br /> o Well screen sections will be perforated with 0.010-inch factory-cut slots. <br /> `' 181-89-719 5 <br />