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define [he pattern fairly well. There were some inconsistencies in [he values derived from holes drilled <br />near each other, but [ha[ was probably due more to interpretative differences than actual differences. <br />Phase 2 tends to have a more uniform deposit than Phase I where the gravel thickness sometimes varies <br />by as much as a factor of two. The drilling information does no[ show those kinds of variations in <br />Phase 2, although [here does appear to be slightly increased variability in [he eastern portions near [he <br />Phase I boundary. This is no[ unexpected as the greatest variation in Phase 1 is in the western portion <br />near the Phase 2 boundary. <br />The cross-sections located at [he end of this exhibit show a sampling of the variations across the <br />site. Sections A and B are for Phase 1 while Sections C and D are for Phase 2 and Section E includes both <br />phases in a west to east direction. The actual mining plan was prepared using many more cross-sections <br />than are presented here. On some of [he planning cross-sections [he gravel layer was fairly consistent <br />across the length of the section and the overburden declined rather evenly toward the river. Bu[ on other <br />sections, primarily in Phase 1, the gravel layer varied widely indicating i[ was deposited on top of a <br />highly variable erosion surface. <br />Probably these variations represent different depths of erosion by the river as it meandered back <br />and forth across former erosion surfaces. This pattern is often seen in fairly swift flowing rivers like the <br />Arkansas. Often the river depth on [he outside of a meander bend is greater where cutting is more intense <br />than near the inside of the bend where cutting is more gentle. Furthermore, the outside of the meander <br />typically has a very steep channel slope while the channel slope on the inside of the meander is usually <br />more gradual. This asymme[ryis evident when adjacent cross-sections are linked laterally. <br />V aria[ions from place to place can also occur because meander changes are not usually smooth or <br />gradual. Instead, meander changes are often induced by major floods. If one could view the changes as if <br />in a time ]apse movie, the changes would make the river channel appear to jump around. As a result of <br />this "catastrophic" change pattern which often occurs in meandering rivers, gravel deposits can vary <br />tremendously from place to place, both with respect to the quality of [he material and the depth and <br />quantity of the material. <br />Another cause for a highly variable bedrock resulting in variable depth could be the existence of <br />paleo-drainages that entered the river valley before there was extensive filling with sediment. These <br />drainages could have produced their own humps and hollows without any relationship to the original <br />main river channel. After filling [he valley with sediment these ancient erosion features can be expressed <br />as locations where the current depth of the deposited gravels are shallow or deep. Interestingly though, <br />the current surface may not exhibit any features that would indicate variations in [he depth of the deposit. <br />Based on the cross-sectioning done in the planning of this gravel operation, it is suspected that <br />considerable variation may be found in the extent and quality of the gravel over such a large site. This <br />variability mainly applies to Phase 1. In Phase 2 such variability in [he sub-gravel shale surface seems [o <br />be largely absent resulting in a fairly smooth sub-gravel topography. These variations are best seen in <br />Pueblo East Pit Amendment 3 (2007) Exhibit D Page 10 of 34 <br />