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the proposed D-portal area, were drilled within the alluvial body associated with <br />Scullion Gulch. Although all the holes fully penetrated the alluvium, no evidence of <br />alluvial ground water was encountered. This information, coupled with the sparse <br />occurrence of deep-rooted vegetation, generally indicates that subirrigation is of <br />minimal consequence along Scullion Gulch. <br />Scullion Gulch Alluvia! Valley Floor Deter-nination <br />The Division and OSM concluded that Scullion Gulch is not an alluvial valley floor, <br />on the following basis: <br />A. Limited subirrigation potential; <br />B. Assessment of regional practices documented by local SCS personnel and the <br />results of a published SCS land inventory; <br />C. Professional judgments of Colorado Division of Minerals and Geology <br />representatives who inventoried the site; and <br />D. Verfial discussions held with the pertnittee confirming the nature of the regional <br />inventory performed. <br />White River <br />Geomorphic Characteristics <br />The White River, a perennial stream, is located along the southern margin of the <br />permit area. The river actually crosses through the southern most tip of the permit <br />boundary for approximately one-half mile. The river meets the geomorphic criteria <br />for alluvial valley floors, as shown on Map 102, as an extensive area of <br />unconsolidated streamlaid deposits are present. The deposits within and adjacent to the <br />permit area appear to range between 1,000 to 1,500 feet wide. The alluvium is about <br />37 feet thick in the general area, consisting of 15 feet of fine silts and clays, with 22 <br />feet of gravel, sand, silt, and clay located below the upper fine-grained material. The <br />pennittee mapped the deposits in the immediate vicinity of the permit area, from a <br />point one-half mile upstream from the eastern margin of the permit area to a point <br />one-half mile downstream from the southwestern portion of the permit area. The <br />deposits are continuous, and extend beyond both the upstream and downstream limits <br />of the area mapped by the permittce. Within the area mapped (approximately 2 miles <br />in length) the alluvial deposits constitute an area in excess of 400 acres. The permittee <br />has indicated that ground water is contained in the alluvium along the White River at <br />depths less than 11.5 feet below the land surface. Subirrigation of deeper rooted <br />vegetation, including alfalfa, likely occurs within this depth. The permittce has <br />indicated; however, that it is a regional practice to artificially flood irrigate alfalfa to <br />maintain a productive crop. Irrigation requirements are therefore not satisfied by <br />subirrigation alone; it is likely, however that subirrigation does supplement the flood <br />irrigation. <br />29 <br />