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0 0 <br /> James L. Tjosvold, P.E. <br /> August 19, 1996 <br /> Page 6 <br /> data. The number of samples sent to the laboratory ranged from one to five samples <br /> per boring. In the workplan, it was estimated that approximately one quarter of the <br /> samples would be sent to the laboratory for analysis. Due to the screening <br /> concentration of 30 ppm chosen for determining which samples would be sent to the <br /> laboratory, 62 samples or 50%—twice the number anticipated in the workplan—were <br /> analyzed for PNA, TPH, and BTEX by the laboratory (as opposed to the planned <br /> 25%). Additional soil samples were also analyzed for STLC, TCLP, pH, cyanide, <br /> grain size analysis, moisture content, and total organic carbon. Therefore, there <br /> were sufficient data from these soil borings to meet the objective of further <br /> characterizing the extent and nature of residues in identified source areas. <br /> Responses to RWQCB comments (dated December 14,1995). <br /> General Comments <br /> Comment: <br /> 1. The site maps using air photos should be replaced with regular computer aided drawing <br /> (CAD) maps. The air photos are appropriate when identifying former structures which could <br /> be potential sources of contamination. Once these structures have been identified, a CAD <br /> map with a convenient scale and incorporating these structures should be used. For example, <br /> Figure 2-5 which is a CAD, is much easier to look at than Figure 4-5. Figure 2 -5 provides <br /> the essential information which is described in the text while Figure 4-5 has extraneous <br /> components which really do not add value to the information being presented but in fact <br /> blurs the picture because of shadows and different shades of gray. Labeling the essential <br /> components also presents a problem because of the varying shades of light and dark. <br /> Response: <br /> 1.We are not aware of any compelling reason to incur the expense of changing the <br /> air photo-based site maps used for the past eight years on this project. The air photo <br /> maps indicate much more detail—not extraneous components—than CAD drawings, <br /> and are useful for locating soil borings, wells, and source areas in the field. The <br /> photo maps have also been useful during interpretation of source area definition <br /> which could not be accomplished using a CAD drawing. <br /> Comment: <br /> 2. References to directions in the Specific Comments assume that north is towards the top of <br /> the page. <br /> Response: <br /> 2. No response required. <br />