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To: Chris Nyikos <br />From: Philip B. Solseng <br />Subject: Stability Analysis Results <br />Date: 16 September 2009 <br />Project: Pond ME Evaluation <br />c: Jed Greenwood, Brad Lindsay <br />4. 10-Year 24-hour Storage Elevation/Storage (both ponds) <br />5. Primary Outfall (Spillway) Storage Elevation/Storage: <br />a. Pond l: <br />b. Pond 2: <br />6. Emergency Spillway Elevation: <br />a. Pond 1: <br />b. Pond 2: <br />7. Top of Dike at Emergency Spillway: <br />8. Upstream Toe Elevation (Bottom of Liner) <br />at Emergency Spillway: <br />9. Natural Ground Elevation Variation: <br />10. Crest Width of Perimeter Dike: <br />11. Slope of Perimeter Dike: <br />12. Liner: <br />6045.0/6.63 acre-feet <br />6051.5/9.2 acre-feet <br />6051.5/9.2 acre-feet <br />6052.5/10.2 acre-feet <br />6052.5/10.2 acre-feet <br />6054.5 <br />6039.5 <br />6048 to 6054 w/ ave. 6050 <br />>12 feet <br />specified in evaluation <br />clay, w/ thickness between 4 and 6" <br />The above information was used in the stability evaluation for the dikes surrounding the pond. <br />As a note, Pond MBSE is about 15 feet deep, but the average height of the embankments above the <br />natural ground is about 4.5 feet. Most of the time and even during flood conditions, the water in the <br />ponds will be below natural ground and stability is not an issue. Therefore, this evaluation addresses the <br />stability of the embankment for the extreme condition when the ponds are at maximum elevation of one <br />(1) foot below the top of dike, water elevation 6053.3. This is a very conservative assumption for <br />evaluating stability and represents a worst case condition. <br />GENERAL ASSUMPTONS FOR POND MBSE <br />The general assumptions for Pond MBSE are as follows: <br />1. Pond MBSE represents two separate ponds. <br />2. The maximum pool elevation is one foot below the crest of embankment at Elevation 6053.5. <br />3. The embankments have a crest width that meets standard dam safety criteria with respect to <br />crest width. Minimum crest width per Design of Small Dams (United States Department of <br />Interior, Bureau of Reclamation, p. 270) is approximately 12 feet.