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<br />Pocharo D. Lamm <br />Governor <br />DEPARTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe, Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON Director <br />III III III IIIIIII III <br />T0: Dan Mathews <br />FROM: Jerry Zimpfer <br />RE: Grand Mesa Alluvial Valley Floor Findings <br />DATE: December 28, 1982 <br />Alluvial Valley Floors <br />AVF Determination <br />The applicant has provided the results of an alluvial valley floor field <br />investigation in the addendum to the permit application (Kimball, et. <br />al., 1982), The extent of the study area is shown on Map I of the <br />addendum. It includes portions of the Williams Creek, Ward Creek, <br />Cottonwood Creek, and Kiser Creek watersheds adjacent to the permit <br />area. The mine itself is located between Ward Creek and Cottonwood Creek. <br />The applicant has identified several unconsolidated stream-laid deposits <br />in the area. The majority of this material occurs as mudflow fans, shown <br />as Qaf on Map 7 of the addendum. There has been some discussion <br />concerning whether or not these mudflow fans (alluvial fans)-the <br />geomorphic criteria for alluvial valley floors. The preamble to the OSM <br />Alluvial Valley Floor Guideline (June 11, 1980) indicates that parts of <br />alluvial fans should be considered for alluvial valley floor <br />determination when they are integrated hydrologically with modern <br />terraces. In this case, the fan deposits are integrated both <br />hydrologically and agriculturally with the modern stream terraces, and <br />should, therefore, be considered in the alluvial valley floor <br />determination. The applicant has also identified four distinct river <br />terraces south of the area which is covered by alluvial mudflow deposits <br />(see Map 7 of the addendum). The uppermost terrace (Qt 4) appears to be <br />part of a dissected pediment which occupies the topographic highs between <br />the stream valleys. It is not a part of the valley bottom complex. The <br />remaining terraces are topographically lower, and are part of the valley <br />bottom complex. <br />The applicant has also provided information concerning water availability <br />for agricultural purposes. These studies focused on the Ward Creek and <br />Williams Creek valleys since these areas may be affected by the proposed <br />mining operations. <br />423 Centennial Building, 1313 Sherman Street Denver. Colorado 80203 Tel. (303) 866-3567 <br />