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Continuous Deflection Separator (CDS) Unit

Continuous Deflective Separation (CDS) systems are structures placed on large storm drain lines to capture floatable trash/debris and sediment from a large drainage area. The units use a vortex action created by the hydraulic energy of incoming flow to separate trash/debris and sediment from the flow. The treated flow is then discharged through the outlet pipe to the storm drain system. During very high storm events, the units are equipped with a bypass system to prevent upstream flooding. Routine CDS system maintenance ensures that the system is operable year-round.

All City installed CDS units meet the Trash TMDL criteria of a * "full capture device."

Due to their cost and potential hydraulic impact on the existing storm drain system; the City has installed a limited number of these systems at strategic locations.

Graphic courtesy of CDS Technologies

* "A full capture system is any single device or series of devices that traps all particles retained by a 5mm mesh screen and has a design treatment capacity of not less than the peak flow rate (Q) resulting from a one-year, one-hour, storm in the subdrainage area. Rational equation is used to compute the peak flow rate: Q=C x I x A, where Q = design flow rate (cubic feet per second, cfs); C = runoff coefficient (dimensionless); I = design rainfall intensity (inches per hour, as determined per the rainfall isohyetal map), and A = subdrainage area (acres)."