Reference Document MCU22/0102 Stormwater Management Plan

    Contents                                           1. Introduction
    1. Introduction					2                              1.1 BIOFILTRATION
        1.1 Biofiltration					2
        1.2 Modular Biofiltration			               3   Biofiltration systems are one type of WSUD system
        1.3 Design Drawings/Dimensions		           3   that have been implemented in urban areas to manage
    2. Applicability Guide				4                        stormwater by reducing peak flows and downstream
    3. Functions					5                                 pollution (Davis & Birch, 2009; Hunt et al., 2008; Le
        3.1 Hydrology					5                            Coustumer et al., 2012). Biofiltration is also referred
        3.2 Sediment					5                             to as bioretention, biofilters and rain gardens in
        3.3 Nutrient Removal				5                      various literature. This report will use the terms
        3.3.1 Particulate nutrient removal 		      5   interchangeably.
        3.3.2 Dissolved nutrient removal		         5
    4. Design					6                                    Biofiltration systems have been popular because of
        4.1 Outlet invert level (Saturated Zone)		 6   flexibility in their design which assists with simple
        4.2 Inlet invert level & type			           6   integration (retrofitting) into existing urban areas
        4.3 Bypass					6                               (Bratieres et al., 2008), as well as new developments.
        4.4 Inlet and outlet configurations		      6   Biofiltration systems are also considered to add to the
        4.5 Surface level set-down			              7   benefits of traditional stormwater quality by including
        4.6 edge interface				7                        aesthetic and social benefits (Mullaney et al., 2015).
        4.7 Plant selection				7
    5. Maintenance					8                               Biofiltration relies on physical, chemical and biological
        5.1 Access 					8                              processes that occur in the various zones including the
        5.2 Inlet structures 				                  8   extended detention depth, filter media and drainage
        5.3 Sediment & Litter removal			           8   layers as indicated in Figure 1. Design modifications
        5.4 Slotted-drainage pipes 			             8   can include a submerged zone beneath the drainage
        5.5 Filter Media Hydraulic Conductivity    8   layer to retain water for enhanced plant survival during
    6. MUSIC Model Application 			                 9   dry weather and denitrification. Stormwater is treated
    7. Summary					9                                   as it filters through the vegetated media, utilising plant
                                                       uptake, microbial processing, adsorption and physical
                                                       filtration to reduce pollutant loads.




                                                       FIGURE 1.
                                                       SCHEMATIC CROSS-SECTION OF A BIOFILTRATION SYSTEM




2       Technical Design Guidelien SPELBasin