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Vermillion Ranch Limited Partnership/Surface Water Impoundment 13659-RX <br /> ' Conclusions <br /> Based on the field exploration and results of our laboratory testing performed for this project, <br /> we make the following conclusions: <br /> 1. Subsoils encountered along the proposed dam centerline consist of alluvial sand and <br /> clay which is considered to have low to moderate plasticity and is generally at or near <br /> full saturation. Soils encountered at the southern abutment and spillway area primarily <br /> ' consist of fine to medium grained sand sized particles and are either non-plastic or have <br /> low plasticity. Seepage of water through the southern abutment soils/spillway should be <br /> evaluated during the design process to determine if such soils may be problematic <br /> ' regarding subsurface erosion and instability. In addition, soil permeability through <br /> alluvial floodplain soils beneath the proposed dam should be performed to identify <br /> 1 problems that may affect overall dam stability and water loss beneath the proposed dam. <br /> 2. During the design process, consideration for water loss into soils within the proposed <br /> ' impoundment area should be considered. Depending on overall topography and soil <br /> permeability, water loss may have a significant impact on reservoir capacity. <br /> 3. Soils most suitable for construction of the proposed earthen dam consist of sandy clay <br /> deposits obtained from the proposed borrow area. Laboratory testing of proposed <br /> ' borrow soils indicate some borrow soils may contain a large fraction of non-plastic silt, <br /> which are generally unsuitable for dam construction due to potential seepage and piping <br /> ' problems. Consequently, care should be exercised regarding source and quality of <br /> proposed borrow material. Alternatively, sandy clay/clay sand alluvium obtained from <br /> the impoundment area located upstream of the proposed dam may be suitable for <br /> construction. Sand and clay alluvium obtained from the proposed impoundment area are <br /> generally at or near saturation and will likely require drying to obtain the optimum <br /> ' moisture content for compaction. <br /> ' 4. Dam foundation soils are considered to be highly compressible and are subject to <br /> consolidation under increased loading from dam embankment soils. Deformation <br /> analysis should be performed during the preliminary design process to determine <br /> tresponse of outlet structures and dam embankment soils to settlement of foundation <br /> soils. In addition, seismic stability analysis of dam foundation soils will likely be <br /> required to estimate a safety factor against liquefaction and dynamic stability of dam <br /> slopes. <br /> ' 5. Detailed deformation analysis of the embankment due to compression or consolidation <br /> of the foundation soils, and evaluation of the outlet or level control structures in <br /> ' response to the deformation should be performed. Development of options to improve <br /> foundation soils and reduce settlement, deformation and distress will likely be required. <br /> ' INBERG-MILLER ENGINEERS <br /> 7 February 26,2009 <br />