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• <br />• <br />• <br />The actual construction of the EMPs will incorporate the site-specific terrain <br />limitations. For example, the most efficient pond is round, but a sharply ovaloid footprint may <br />function the best and more of a practical design for a site. The pond recommendations <br />included within this report are the minimum volume and footprint area required, rather than <br />specific dimensions for that reason. The footprint can be constructed to any shape as long <br />as the required volume is achieved for the EMP. <br />Sediment Removal Efficiency and Performance <br />Laboratory tests were conducted on samples of growth medium, sub-soils, and <br />pond sediment to verify that the pond sizing criteria is appropriate and that their <br />performance will be at least equal to that of natural structures and soil conditions. Those <br />tests show that the ponds, as designed, will remove all but colloidal clays approximately <br />one micron in size. Removal of such colloids would not be expected by settlement in <br />any pond. They compose about 2% of the sediment that is less than 10 sieve (1.7 mm). <br />Figure 5 shows results of a hydrometer test on the natural soil samples, allowed to soak <br />overnight before testing (but with no dispersants added). <br />The graphs show that all but the colloids will settle in about one to two hours and <br />will result in 94 to 98 percent removal efficiency. The residence time of the EMP's <br />during both design storms were compared with the laboratory results. Maximum <br />removal efficiency is expected from each of the ponds that are sized to contain twice the <br />10-year/24-hour? storm volume. <br />Client:CC&V Gold Mining Co. <br />Title: Storm Water Management, MLE <br />4/11 /08 <br />Page 13 <br />