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ALLUVIAL VALLEY FLOORS <br />Supplemented with previous investigations conducted for the <br />Marr Strip Mine permit application and the July 21, 1980 Canadian <br />Strip Mine TEA, sufficient information has been presented in this <br />permit application to make alluvial valley floor determinations <br />for both the North Fork of Bolton Draw within the permit area and <br />the main channel of Bolton Draw below the stockpond. The AVF in- <br />formation is located on pp. 106-116, Volume 1 of the permit <br />application. A third area, comprised of Bolton Draw alluvium <br />extending along North Fork between the eastern permit boundary <br />and the stockpond, remains in question. Bolton Draw and its <br />tributary, North Fork, are the only streams that will actually be <br />impacted by mining at the site (see Exhibit 2, Vol. 1 of the per- <br />mit application). Impacts to the Canadian River AVF will be <br />similar to those experienced in Bolton Draw, although to a lesser <br />degree. <br />rth Fork of Bolton Draw Within the Permit Area <br />Although the North Fork of Bolton Draw possesses some <br />characteristics typical of an alluvial valley floor, the majority <br />of the evidence suggests that a negative determination is appro- <br />priate. Within the permit area, two prerequisites for an AVF <br />have been identified: a unit of alluvium and an area of subirri- <br />gation. Both areas exceed the minimum width criteria of 50 feet <br />recommended in the OSM June 11, 1980 AVF Guidelines (Part I, p. <br />5), but only the 14.4 acre unnamed alluvial soil unit exceeds the <br />recommended 10 acre areal extent; the subirrigated area comprises <br />only 5.4 acres. Furthermore, this subirrigated area has a <br />perched water table, isolated from the main alluvial water table <br />downstream, and is recharged solely by precipitation. Therefore, <br />the viability of classifying North Fork as an alluvial valley <br />floor on the basis of these two characteristics is, at best, <br />questionable. <br />-84- <br />