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Technical Memorandum <br /> Phase 2 Sediment Pond Jurisdictional Dam Evaluation ■ <br /> NewFields Job No.475.0106.006 <br /> August 8,2016 <br /> Maximum Normal Water <br /> Level at Spillway Crest Crest Do+narstream fb,Spillway Freeboard <br /> Width <br /> Slope <br /> i <br /> ---- <br /> i <br /> H 1 <br /> j H o <br /> / V <br /> y L E_ <br /> 2E <br /> f � <br /> Upstream <br /> Slope <br /> i <br /> N-- ; -►� H <br /> I � V <br /> 1 <br /> Centarline of Dam <br /> Adjust for slope of <br /> natural terrain <br /> s.Slope of Natural Terrain <br /> Determination of Dam Vertical Height at the Maximum Cross Section <br /> Figure 2 <br /> 3.0 ENGINEERS EVALUATION <br /> NewFields compared the as-built and pre-construction or native survey data for the Phase 2 <br /> Sediment Pond. Utilizing AutoCAD Civil 3D, the storage capacity, surface area at the high-water <br /> level, and height of the dam along the centerline of the emergency spillway were evaluated. As <br /> shown in Figure 1, the Phase 2 Sediment Pond Dam has the following geometric attributes. <br /> A storage capacity of 12.07 acre-feet measured below the emergency spillway invert which <br /> is far less than the jurisdictional threshold storage capacity value of 100 acre-feet. <br /> A water surface area, of 1.02 acres, measured at the emergency spillway invert, which is far <br /> less than the jurisdictional threshold value for area, of 20 acres. <br /> A dam height measuring 6.S vertical feet from the spillway invert to the embankment toe at <br /> natural ground. The measured dam height of 6.5 feet was determined from as-built and <br /> native ground survey data and is less than the jurisdictional height threshold value of 10 <br /> feet. <br /> To verify the as-built pond survey, NewFields compared the elevations of the Phase 2 Sediment <br /> Pond to the flyover data performed in 2015. The elevations between the two surfaces were <br /> determined to be consistent. It should be noted however, that this evaluation used as-built <br /> ground survey, since it is considered to be the more accurate of the two methods of survey <br /> available. <br /> Page 4 <br />