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3. Decant Line <br /> The water pool of Mayflower Tailing Pond will be removed by the use <br /> of a decant line with risers. The decant "line" is actually two <br /> pipes laid side-by-side. The steel pipes are 42-inches in diameter, <br /> laid in 20-foot segments, enveloped in reinforced concrete, and con- <br /> nected with Dresser couplings and shear pins. The line has been de- <br /> signed for loading according to the ultimate profile of the dam, and <br /> instrumentation has been installed under the decant line to monitor <br /> weight stress. <br /> In May 1975, the ice on Tenmile Tailing Pond melted around the edges <br /> and during a high wind it shifted and sheared off No. 16 Decant Riser. <br /> The result was a loss of water through the sheared off riser in excess <br /> of sixty thousand gallons per minute, and a potential threat to the <br /> stability of the dam. Repair crews worked around the clock for seven <br /> days to repair the damage. <br /> To prevent a recurrence of this failure, Climax designed a riser that <br /> would not be adversely affected by ice, yet still be compatible with <br /> our proven decant system. The result of this design is the Side-Hill <br /> Riser. The first side-hill riser was installed on the Mayflower Tail- <br /> ing Pond decant line in 1977, and consists of a twin riser tower laid <br /> on its side in a cut in the hill and then backfilled with concrete. <br /> Each riser has a vertical height of 60 feet, and risers are spaced such <br /> that two risers will always be in the water pool at any given time. <br /> r. <br /> ,{•,.'� ♦ �`S q' ♦ 0' ',� <br /> r"` 'Y�_i-^2 f m`.e' � x<:' ' ,--•�ice?: <br /> Figure 5. Side-Hill Riser <br />