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Comment noted. <br />5. Your net Dawson sand thickness map (figure 10) looks good and is largely driven by the <br />pattern of modern erosion. <br />Comment noted. <br />6. The top and bottom of the Denver aquifer maps (fig 11 and 12) look complex because of the <br />data base, not because of complex geology (see above comment). This arbitrary assignment of <br />aquifer boundaries makes all subsequent analyses and models arbitrary. You will see bulls eyes <br />on your net sandstone map (figure 13, for example in central Arapahoe County) that are probably <br />the results of your data set rather than the geology. <br />Comment noted. <br />7. On figure 11 there is a line, not shown, that represents where the top of the Denver aquifer hits <br />the surface of the ground. Outside of this line I presume your "top Denver aquifer" is actually the <br />surface of the earth minus any alluvial aquifer thickness. Carefully made maps could show this <br />line and would be expected to have quite different contouring patterns in the two realms (inside <br />and outside of the line). <br />Existing geophysical logs were used to delineate the top of all of the bedrock aquifers and <br />additional control was added, using engineering judgment, to the outside edge of the bedrock top <br />surface in areas where insufficient data existed to perform contouring. The "outcrop "areas of <br />the bedrock top surfaces were limited to be less than or equal to either ground surface or the <br />base of alluvial paleochannels as noted in Sections 1.2.6 and 1.2.7. <br />8. Your figure 20 illustrates the problems associated with the reliance on the state picks. <br />Compare it to figure 11 of Raynolds, 2004 (in that Mt Geologist issue mentioned above) which <br />maps almost the same thing. Between pick differences and sand-count differences, there is a lot <br />of variability in how the data can be handled. Again as per my comment above, once you are <br />committed to the State data base there is not much that can be done to make the maps look more <br />"geologically reasonable". <br />Comment noted. It is felt that the cited figure reasonably depicts net sand thickness of this <br />aquifer layer. <br />9. Your figure 21 illustrates the data base working well. This is because the top of the Fox Hills <br />Sandstone is an "easy pick" (most geologists would agree) hence you see a geologically <br />reasonable map. My point with concern on other picks discussed above is that all the structure <br />maps (=Top Elevation) should more or less resemble this simple, smooth pattern.....because (in <br />my opinion) the geology is not that complicated. <br />Figure 22 is a bit more noisy because the bottom of the Fox Hills is harder to pick <br />unambiguously. <br />