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Attachment A <br /> 4 <br /> Volumes V & VI <br /> o Clarification of source of data for transmissivity values <br /> on page G-7 should be provided. <br /> o Values of transmissivity used in the model for layer 2 <br /> (the intermediate zone) are 40 , 000 to 160, 000 gallons per <br /> day per foot. The Department requests additional detail <br /> as to the distribution of the various values used in the <br /> model. <br /> -7 <br /> 0 The values of vertical conductance (approximately 10 ) <br /> are interpreted to be very low. A range of values <br /> (large) should be run with result included in the report. <br /> o Table B-2 values are viewed with skepticism. Apparently, <br /> the sample was taken from the MW-462 borehole at a depth <br /> of 188 feet below surface. It appears this sample was <br /> one of the finer-grained portions in that borehole. The <br /> geophysical log shows that there are many portions of the <br /> borehole which are much more resistive (coarser-grained) <br /> than that interval . Thus, it is uncertain that a <br /> hydraulic conductivity determined from this interval is <br /> representative of the entire aquitard, and that the <br /> average_.rertical hydraulic conductivity is much larger <br /> than 10 <br /> Therefore, the Department requests MODFLAW simulations be <br /> run with a range of vertical hydraulic values. <br /> o Figures G-10 and G-11 are projected water flow paths for <br /> Case 3 - layer 1, and Case 3 - layer 2 , respectively. <br /> These figures show ground water flow arrows, but do not <br /> show potentiometric data ( or potentiometric contours) . <br /> Potentiometric data and contours for Case 3 should be <br /> presented. This information is necessary to confirm that <br /> simulations will capture contaminated water. <br /> o The model simulates flow from pumping extraction well one <br /> (EW-1) and eight hypothetical extraction wells. It is <br /> unclear as to the screen depths and lengths used in the <br /> model . Revisions to the final RI/FS -report should <br /> include this information. <br /> o All borehole lithologic logs and as-built well <br /> construction diagrams should be included in the final <br /> version of the RI/FS. <br />