Site design should also consider avoiding sediment from entering the pavement areas by directing stormwater runoff away from the pavement installation area . Sedimentation can prematurely clog the aggregate layers and pavement materials and make replacement necessary . This is particularly important to consider when working with adjacent landscaped areas that can be significant sources of sediments . Building the pervious surfaces above soil surfaces and placing barriers around the perimeter are some options to consider . This will reduce the potential maintenance costs associated with maintaining the system ’ s function overtime .
Permeable pavement systems can have up to five layers of material . These layers consist of 1 ) permeable pavement surface material , 2 ) bedding course , 3 ) choker course , 4 ) reservoir base course , and 5 ) soil subgrade . An optional geotextile can be included between the reservoir and subgrade to prevent settling of reservoir stone in the surrounding soil ( UF IFAS ; Bean 2019 ). Refer to the diagram below for a breakdown of these components .
PERVIOUS PAVEMENT SYSTEMS
Figure 25 . Cross section of a typical permeable pavement system . ( WEF-Stormwater Report ; UF-IFAS ; Bean 2019 ).
The very bottom of the site is the subgrade soil layer . These soils are the native soils found naturally and exposed following site excavation . For systems designed to infiltrate into the soil subgrade , the bottom of the system needs to be 2 feet above the seasonal high-water table . Therefore , the system has time to recover storage capacity between events by infiltrating into the available pore space within the soil subgrade ( UF IFAS ; Bean 2019 ). The subgrade ’ s line , grade , and elevations need to be included within the plans to allow uniform infiltration on site . Infiltration and load-bearing capacities need to be included within the design parameters in regards to the subgrade materials . The County may require additional subbase materials to compensate for the structural support capacity of existing native soils . Compaction of the subgrade area needs to be prevented by including the use of light equipment and scarification techniques in the installation plan .
FALL 2022
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