Detailed Stormwater Management Practice Design - Tauranga City ...

SMG-9 Figure 10 - Linear Sand Filter
The treatment process is the same for all three of the practices but SMG-9 Figure 8
Sand Filter Basin allows for peak flow control in addition to water quality treatment.
The other two figures provide water quality control only.
An important consideration of sand filter performance is the diversion of larger flows
around the filter. Having high flows enter the filter with an overflow in the filter will
significantly reduce performance as turbulent flow will allow for finer sediments to
pass over the filter bed. In a similar fashion, hydrocarbons having a specific gravity
less than water will pass over the filter into the overflow pipe.
A simple way to prevent contaminants from exiting the filter is to have a flow
diversion structure placed prior to the sand filter. This is a simple design, especially
when the flow into the filter is through a pipe. SMG-9 Figure 11 Diversion Weir
provides a schematic of how the flow diverter can be designed so that the water
quality storm passes through the sand filter and larger flows bypass it.
Page 21 Updated 01/11/2012