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Flatiron Afterbay Dam

Photo of Flatiron Afterbay Dam
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The zoned and compacted earthfill-type dam provides for the retention and regulation of water discharged into Chimney Hollow from Flatiron Powerplant. It consists of an impervious central core flanked by zones of relatively free-draining material grading to pervious at the outer slopes of the dam. The upstream zone is designed to resist percolation of the afterbay water and to dissipate internal pressures exerted outwardly during rapid afterbay drawdowns. The downstream zones protects the impervious central core and stabilizes the dam by lowering the saturation line in the downstream area. The cutoff trench beneath the dam is designed to obstruct percolation along the foundation contact to prevent dangerous seepage velocities. The stability of the dam is further safeguarded by the embankment toe drains which intercept seepage along the foundation contact and surface flow from within the dam. The toe drains are designed to permit easy escape of the seepage and to lower the ground water table sufficiently to avoid the formation of boggy areas below the dam.

Last updated: Mar 29, 2013