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I Subsurface Conditions <br /> Based on results of the field investigation and GEI's knowledge of the site, the soil and <br /> bedrock conditions can be broadly categorized into the following three units: <br /> • Fill <br /> • Coarse alluvium <br /> • Pierre Shale bedrock <br /> This section briefly summarizes each of these units. A more thorough discussion of the units <br /> and how they are anticipated to impact interconnect construction is contained in the project <br /> Geotechnical Baseline Report (Brierley, 2014). <br /> 3.1 Fill <br /> The fill material generally includes recently constructed slope liners in Overland Ponds Pond 2. <br /> The fill encountered in Treiber A was placed as a temporary cover or buttress during mining <br /> activities, and is currently being re-graded and/or replaced and reconstructed for final slope <br /> reclamation. The fill materials primarily range from clayey sands to sandy clays, and gradation <br /> testing shows the percent passing the 200 sieve ranging from 12 to 52 percent. Liquid limits <br /> and plasticity indices ranged from not liquid to 30 percent and not plastic to 15 percent, <br /> respectively. Moisture content results ranged from 4 to 21 percent. Laboratory testing results <br /> are included in Appendix B. <br /> Some fill material consists of loose sand and gravel with silt, possibly spoils left from mining <br /> or cutoff wall construction. This material was encountered in test pits throughout Treiber A. <br /> This material varied in thickness and ranged from between 4 to 13 feet on the side slopes and <br /> 1 to 5 feet on the reservoir floor. <br /> 3.2 Coarse Alluvium <br /> The alluvial material consists of the sand, gravel, and cobble that were historically mined for <br /> aggregate products (pit run). The coarse nature of the material is due to the close proximity <br /> to the Rocky Mountains, as the Cache la Poudre River carries sediment from the mountains <br /> and deposits the coarse alluvial material in the plains as the rivers lose energy. <br /> This alluvial material generally consists of medium to coarse grained sand and gravel with <br /> cobbles and is typically very dense. Laboratory testing indicates the sand and gravel <br /> typically has less than 10 percent fines passing the No. 200 sieve. Laboratory testing results <br /> are included in Appendix B. <br /> G E I Subsurface Conditions 1 8 <br />