2005-07-19_GENERAL DOCUMENTS - C1981018

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the permittee based on the type of vegetation present along the drainage. The pennittee has identified a big sage brush - greasewood community along the entire length of unconsolidated alluvial deposits identified on Map 102, and concludes that water is available to the vegetation "on a limited and sporadic basis". The big sage brush-greasewood community, however, is more spazse compazed to that community found along Red Wash, indicating that the availability of subsurface water is much more limited in Scullion Gulch. Further evidence of the general lack of subimgation can be gleaned from the permittee's surface facilities geotechnical investigation, contained in Illustration 18 of the permit application. Six exploration holes, sited at the proposed D-portal area, were drilled within the alluvial body associated with Scullion Gulch. Although all the holes frilly penetrated the alluvium, no evidence of alluvial ground water was encountered. This information, coupled with the sparse occurrence ofdeep-rooted vegetation, generally indicates that subirrigation is of minimal consequence along Scullion Gulch. Scullion Gulch Alluvial Valley Floor Determination The Division and OSM concluded that Scullion Gulch is not an alluvial valley floor, on the following basis: A. Limited subirrigation potential; B. Assessment of regional practices documented by local SCS personnel and the results of a published SCS land inventory; C. Professional judgments of Colorado Division of Minerals and Geology representatives who inventoried the site; and D. Verbal discussions held with the permittee confirming the nature of the regional inventory performed. Geomorphic Characteristics The White River, a perennial stream, is located along the southern mazgin of the permit azea. The river actually crosses through the southern most tip of the permit boundary for approximately one-half mile. The river meets the geomorphic criteria for alluvial valley floors, as shown on Map 102, as an extensive azea of unconsolidated streamlaid deposits aze present. The deposits within and adjacent to the permit area appear to range between 1,000 to 1,500 feet wide. The alluvium is about 37 feet thick in the general azea, consisting of 15 feet of fine silts and clays, with 22 feet of gravel, sand, silt, and clay located below the upper fine-grained material. The permittee mapped the deposits in the immediate vicinity of the permit area, from a point one-half mile upstream from the eastern mazgin of the permit area to a point one-half mile downstream from the southwestern portion of the permit azea. The deposits aze continuous, and extend beyond 47