Slide 23 of 43
Notes:
As with all other filtering practices, pretreatment is necessary to extend the practice's functional life, as well as to increase the pollutant removal capability. Wet and dry swales should incorporate at least nominal pretreatment as a component of the system design. The difference with these practices from other filtering practices is that the pretreatment component is more qualitative in nature and is an integral part of the practice itself (e.g., the side slopes of the grass channel). The design components for pretreatment which are specific to dry and wet swales are presented in this slide. With the exception of sizing a forebay at the initial inflow point, there are no specific, quantitative sizing criteria for these pretreatment components.