greater load bearing capacity can be achieved by building a thicker underlying gravel reservoir layer ( Cetin , 2013 ). Below is general guidance on the use of the various pervious surface options :
Porous Concrete ( PC ) - Consists of a mixture of Portland cement , water , and coarse gravel aggregate ( 9.5-12.5 mm ). Maintains a porosity between 15-25 % ( Bean et al . 2019 ). Base color is consistent with gray color similar to traditional concrete , which can be altered with additives . Can be used in driveways , walkways , bike paths , and similar applications ( Farny , 2004 ).
Porous Asphalt ( PA ) - Consists of a mixture of asphalt and coarse gravel aggregate ( 9.5-12.5mm ). Maintains a porosity between 18-25 %. Base color is dark gray to black , similar to asphalt . This can be used in all applications from walkways to busy highways depending on the depth of the reservoir layer ( Cetin , 2013 ; Federal Highway Administration , 2012 ; Bean et al . 2019 ). Recommended for use in high traffic areas .
Permeable interlocking concrete pavers ( PICP ) - Precast concrete paving units which have notches to create spaces between pavers . They can be used in a variety of residential and commercial applications , including driveways , pool decks , pedestrian areas , parking lots , and similar applications . Maintains a porosity between 5-15 % ( Bean et al . 2019 ). Comes in a variety of neutral and earth tone colors , such as gray , brown , and red . Commonly used examples include Belgard ’ s Aqualine and Aqua Roc lines .
Plastic reinforcing grids with turf ( PRG ) - Premade , heavy-duty plastic ( HDPE ) grids with voids for fill material . They can be used in a variety of residential and light commercial applications , including driveways , overflow parking lots , and similar applications . Maintains a porosity between 20-40 %, depending on material filled within the voids ( Bean et al . 2019 ). Plastic material comes in black , green , and red tones . Fill material varies upon availability , but can be overlaid with green vegetated turf .
Figure 24 . Permeable pavement surfaces , left to right : permeable interlocking concrete pavers ( PICP ), porous asphalt ( PA ), porous concrete ( PC ), and plastic reinforcing grids with turf ( PRG ) ( as adapted from Bean , 2019 & Sprouse , 2020 ).
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NATURE-BASED SOLUTIONS MANUAL FOR KIAWAH ISLAND