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Pond NHN-001 As -Built <br />Emergency Spillway <br />The following SEDCAD runs, including a 10 year -24 hour event with 2-6" weep holes open and <br />a 25 year -24 hour event with 2-6" weep holes closed for the as -built pond show no discharge <br />through the emergency spillway; therefore, no emergency spillway flow is indicated for use in <br />calculating freeboard. The minimum freeboard resulting from these SEDCAD runs occurs during <br />the 25 year -24 hour weep holes closed case, where the peak pool stage elevation is 5,677.46 feet. <br />This provides for 2.04 feet of freeboard to the top of the dam at 5,679.50 feet. The emergency <br />spillway has been built to an elevation of 5,677.50 feet, two feet lower than the top of the dam <br />embankment. The approved Pond NHN-001 design done by Arcadis included a 25 year -24 hour <br />SEDCAD run assuming no flow through the primary spillway, resulting in a flow depth through <br />the designed 10 feet wide, 2:1 side slope emergency spillway of 0.18 ft. The resulting freeboard <br />in such a scenario is 1.82 ft. In this worst case situation, where the primary spillway would <br />become blocked, the emergency spillway as built would still have greater than the required 1.00 <br />feet of freeboard. The emergency spillway is a combination of a rip -rapped trapezoidal channel, <br />minimum 10 feet wide with 2h:Iv or flatter side slopes which flows into a 72" concrete drop <br />inlet. This drop inlet feeds a 24" barrel CMP which then flows to outlet as shown on drawing <br />2.05.3(4)-6. SEDCAD runs have been revised to reflect this condition. <br />Embankment <br />Foundation preparation of 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. The engineering design for <br />construction of Pond NHN-001 specified at least 90% Modified Proctor Density, ASTM D-1557, <br />routine compaction standard for embankment construction. Actual constructed lifts were <br />calculated to be an average of 10.7 inches in thickness. The faces and slopes of the embankment <br />are being planted during the first growing season to establish vegetation. The freeboard of the <br />pond during the sudden increase in volume as a result of a 25 year -24 hour event is 2.04 feet. <br />This freeboard is sufficient to prevent overtopping by waves. <br />Appendix 2.05.3(4)-6 Page 1 February 2017 (TR -15) <br />