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t • . <br /> k" KLEINFELDER � � <br /> September 10, 1987 <br /> File: 24-2041-3 ENVIROMENTAL HEA�TN <br /> PERMIT/SERVICES <br /> Antonia K.J. Vorster <br /> Senior Engineer <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 3443 Routier Road <br /> Sacramento, California 95827-3098 <br /> Dear Ms. Vorster: <br /> In consideration of your comments regarding the report entitled "Ogden <br /> Food Products Corporation Soil and Ground Water Investigation, Stockton, <br /> California," Kleinfelder is taking the opportunity to address your <br /> concerns. We will address your second comment regarding PID and <br /> calibration to a benzene standard first. This will assist in addressing <br /> the set of comments concerning contaminant contouring and sample analysis. <br /> A portable organic vapor detector (PID) was used to screen soil samples <br /> collected during the investigation. The instrument used was a Photovac <br /> TIP with a 10.6 eV photoionization lamp. A 25 ppm benzene (9.25 eV) <br /> calibration gas was selected and used to set a reference for relative <br /> comparison of the field readings. The TIP does not distinguish between <br /> different constituents. The field screening reading could represent a <br /> composite of one or more different ionizable constituents. A positive <br /> field reading from a TIP calibrated with benzene does not necessarily mean <br /> that benzene is present. <br /> It should be noted the PID was used to screen the soil samples and not the <br /> water samples. Some information on the TIP from the manufacturer is <br /> included for your review. <br /> Your first set of comments concern the contouring tof fuel oil <br /> contamination. Plates 4, 5, 6, and 7 are computer generated contaminant <br /> contour maps based on the qualitative PID field screening of 46 soil <br /> samples. Plates 8,9, and 10 are computer generated contaminant contour <br /> maps based on quantitative TPH analytical results for 22 soil samples. As <br /> the PID is a qualitative field instrument and field readings can be <br /> influenced by soil type and temperature, no attempt was made to assign TPH <br /> values based on PID readings. The TPH computer contours were generated on <br /> limited data points and some zero values were assigned to provide limits <br /> for the computer (Boring B-5 10' Plate 8, Boring B-9 10' Plate 8, Boring <br /> B-4 15' Plate 9) . The 10 foot samples in Borings 5 and 9 had a PID <br /> reading of .5 ppmv which is relatively low compared to the other positive <br /> PID readings. Boring 4 was assigned a zero value to provide a limit so <br /> the contour could be constructed. Limited TPH information was obtained <br /> from a depth of 18 to 20 feet due to depth of ground water. Ground water <br /> was generally encountered from 10 to 15 feet below the ground surface. <br /> Soil samples were not collected below the depth where ground water entered <br /> the boring. <br /> KLEINFELDER 9795 Business Park Drive, Suite C, Sacramento, CA 95827 (916) 366-1701 <br />