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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I I <br />I <br /> <br />source of suitable aggregate for RCC. The alternatives included <br />quarrying the granitic bedrock exposed in the valley walls, hauling <br />aggregate from the Yampa River about 12 miles to the west or from the <br />Kremmling area about 27 miles to the east, or utilizing the alluvial <br />sand and gravel available in the river flood plain. Yampa River <br />sources have not been developed and would require investigation. The <br />Kremmling site is a proven commercial source. <br /> <br />Gradation tests of the Rock Creek alluvial deposits performed previ- <br />ously indicated that although the natural gradation was only fair, the <br />deposits could, with appropriate processing, be a suitable source for <br />RCC aggregate. Due to the accessibility and proximity to the site, the <br />alluvium was easily the most economical source. Therefore, all sam- <br />pling and testing was done on material derived from these deposits. <br /> <br />Initially three test pits were excavated into the gravel deposits to <br />ascertain the depth, to visually classify the material, and to obtain <br />samples for laboratory testing. The first two pits were excavated in a <br />tributary valley to Rock Creek that was perched above the main valley <br />floor. These pits showed the material to be too fine and the deposit <br />to be of limited thickness. One test pit was excavated in the stream <br />bed alluvium about 2 miles upstream of the damsite at the base of <br />steeply sloping debris deposit. This site was determined by access <br />limitations in the Forest Service Permit. The pit was excavated to a <br />depth of 12 feet. Visually the material appeared to be a rocky, sandy <br />soil strewn with organic material. The material was a mixture of <br />alluvial sand and gravel and angular cobbles of mechanically trans- <br />ported slide debris. It did not fit the visual description of the <br />material in the previous investigation, however, the gradation corres- <br />ponded closely. As aggregate for RCC can bridge a wide range of physi- <br />cal characteristics samples of the material were obtained for labora- <br />tory testing and an RCC trial mix program. A source of potential fine <br />blend material was investigated about 4 miles upstream from Site B. <br />This material is derived from weathering of the Browns Park Formation <br />and could be used inexpensively to increase the amount of fines in the <br />RCC gradation. <br /> <br />3 - 11 <br /> <br />681 gw/502o.1 <br />