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Two Rivers Gravel Pit Mine <br /> Riverside Berm Failure Analysis <br /> and Flood Control Mitigation Plan <br /> 7ech"olooicess January 22,2020 <br /> 2.2Topography <br /> The site is relatively flat north and south, and gradually slopes from west to east with elevations <br /> ranging from about 4688 ft to 4679 ft. <br /> 2.3. Local Roads <br /> County Road 396 passes through the Site in addition to private roads for the purpose of farming <br /> and gas well operations. <br /> 2.4. Surrounding Development <br /> Surrounding development is rural and industrial consisting of farmland, and oil and gas wells. <br /> The site is mainly used for agricultural purpose and contains a dwelling, barn, and garage. Other <br /> than that, it is mainly undeveloped. <br /> 2.5 Oil and Gas Wells <br /> One gas facility is located on the eastern-most edge of the site in the approximate north-south <br /> center. Natural gas and oil wells, including collection and conveyance facilities, are located <br /> throughout the site. <br /> 2.6 Soils and Vegetation <br /> Soil conditions generally consist of varying thicknesses of top soil underlain by sand and gravel <br /> deposits. A detailed soil description and geotechnical information is contained in Geotechnical <br /> Investigation (WesTest, 2015). Vegetation consists of trees, grasses, and shrubs on the riverbank, <br /> and native grasses on the site.. <br /> 2.7. Drainageways <br /> As previously mentioned, the Big Thompson River flows along the northern portion of the Site <br /> from west to east(Figure 2), and the South Platte River flows along the southern portion of the <br /> site from west to east. The Site is located in the floodplain of each river. <br /> 2.8. Potential for site flooding <br /> All of the site is located in the FEMA 100-yr floodplain (Figure 3) (Weld County Online <br /> Mapping). Because the site has a high potential for flooding (being located between two rivers in <br /> a flat floodplain), earthen flood control berms—with heights from about 3 to 6 ft) -were <br /> constructed around the site and appear in good condition. The earthen berms were likely <br /> constructed by land owners (assuming in the late 1940's based on aerial photos)to protect their <br /> pg.8 <br />