CTMP Revision 0 Rainwater caught by the catchment tray is piped into a header tank, and then into a displacement tank which floats in a larger tank containing the flocculant filled to the level of an outlet pipe leading to the sediment laden diversion about 10m upstream of the inlet of the sediment control device. The greater the rate of rainwater flow into the displacement tank the greater the flow of flocculant into the sediment laden runoff channel. The header tank is designed to provide for no dosing during the initial rainfall of up to 12mm of rain under dry conditions to reflect the lag time between the onset of rainfall and the arrival of runoff at the device. The dual outlet of the header tank outlet also attenuates chemical flow during the initial stages of a storm and after rain has ceased at the end of a storm. Figure 3: Components of the floc shed. A mini Floc Shed (Figure 4) or Floc Box (Figure 5) is well suited for DEBs with catchment areas less than 3,000m2 and are set up in a similar way to the traditional floc shed outlined above. Figure 2: Traditional floc shed schematic.
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