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POND NHN-001 AS-BUILT <br /> Pond Construction and Compliance Demonstration <br /> The as-built drawing for Pond NHN-001 is provided on Map 2.05.3(4)-6 and includes a plan <br /> view, cross-sections and stage-storage curve. The principal spillway consists of a riser at <br /> elevation 5675.50 feet, with a 24-inch diameter pipe, an 18-inch diameter restrictor plate, and a <br /> pair of valved 6-inch diameter weepholes at elevation 5671.50 feet. The emergency spillway is a <br /> combination rip-rapped trapezoidal channel at elevation 5676.50 feet (minimum 15 feet wide <br /> with 2h:1 v or flatter side slopes) which flows into a 72" concrete drop inlet. The drop inlet feeds <br /> a 24-inch diameter CMP which then flows to outlet(see Map 2.05.3(4)-6). <br /> SEDCAD was used to analyze hydrology and sedimentology and the demonstration indicates <br /> Pond NHN-001 is adequate to store the 10-YR, 24-HR storm event and five (5) years of <br /> accumulated sediment. With the weepholes open, the peak water level is 5674.35 feet, which is <br /> 1.15 feet below the principal spillway riser and 2.15 feet below the emergency spillway channel. <br /> The SEDCAD demonstration for the 25-YR, 24-HR storm event indicates that with weepholes <br /> closed, Pond NHN-001 will safely convey the peak discharge with 1.01 feet of freeboard from <br /> the peak level (5676.99 feet)to the top of the structure(5678.00 feet). <br /> Embankment <br /> Foundation preparation for the embankment of Pond NHN-001 included removal of vegetative <br /> and organic materials and scarification of the ground. The embankment fill material was <br /> constructed free of sod, roots, vegetative matter and frozen soil. Lambert and Associates on-site <br /> compaction testing services were utilized on an as-needed basis and their testing methods were in <br /> accordance with ASTM Test Method, D2922 and D3017, for Nuclear Moisture Content and Dry <br /> Density for accepted material testing practices in the area. All final field density tests indicated <br /> 90% or greater relative compaction. The faces and slopes of the embankment are being planted <br /> during the first growing season to establish vegetation. <br /> Additionally, Lambert and Associates performed a slope stability analysis of the embankment <br /> using "Slope Stability Analysis" by Geosoft computer software. Their stability analysis <br /> considered a crest width of 10 feet, embankment height of 9.5 feet and embankment inclination <br /> of 3h:ly (upstream and downstream). This configuration applies only to the theoretical stability <br /> assessment, for actual side slopes measurements at specific locations, refer to Map 2.05.3(4)-6. <br /> The analysis indicated a theoretical factor of safety of 1.53 for the pond embankment. <br /> Appendix 2.05.3(4)-6 Page 1 December 2018 (TR-19) <br />