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Geotechnical Engineering Report <br />Gravel Evaluation - Saddlehorn Ranch Site <br />NE of Highways 257 and 60 -Milliken, Colorado <br />Terracon Project No. 21015136 Terracon <br />o Plasticity Index <br />SITE CONDITIONS <br />The site consists of pasture land vegetated with native grasses and weeds. Cottonwood trees line <br />the banks of the Big and Little Thompson rivers, which flow through the site and meet at the eastern <br />edge of the project area. The site is located in the flood plain of the two streams and is relatively flat. <br />Drainage in the area is into the streams, which flow generally to the east. A steel truss bridge spans <br />the Big Thompson River in the central portion of the property. The site is bordered on the north, <br />east and west by farmland and on the south by residential and agricultural properties. <br />SUBSURFACE CONDITIONS <br />Soil and Bedrock Conditions <br />As presented on the Logs of Boring, surface soils to depths of 2 to 16 feet consisted of overburden <br />materials. The upper 6 inches of the overburden consisted of topsoil. The topsoil has been penetrated <br />by root growth and organic matter. The underlying overburden consists of sandy silt and silty sand <br />with minor amounts of sandy lean clay. A layer of poorly graded to well graded sand with silt and <br />gravel varying in thickness from 14 to 29 % feet was encountered below the overburden in all but <br />boring T-t3. Bedrock underlies the sand with gravel at depths of 16 to 35 feet below the surface. The <br />bedrock consists of interbedded siltstone and claystone with minor amounts of sandstone. <br />Field and Laboratory Test Results <br />Field test results indicate that the sand with gravel is very loose to medium dense in consistency. <br />Laboratory test results indicate that the sand is poorly graded and non plastic. <br />Groundwater Conditions <br />Groundwater was encountered at approximate depths of 2.5 to 7.5 feet in the test borings at the time <br />of field exploration. When checked 1 day after the drilling, groundwater was measured at approximate <br />depths of 2 Yz to 7 Yz feet. These observations represent groundwater conditions at the time of the <br />field exploration, and may not be indicative of other times, or at other locations. Groundwater levels <br />can be expected to fluctuate with varying seasonal and weather conditions as well as the volume of <br />flow in the Big and Little Thompson River. <br />3 <br />