How to simulate the presence of a paved surface?

In case the soil on the site under study is paved, you can simulate the presence of a pavement (asphalt, concrete) by creating a top soil layer  on the Soil tab (the soil type of this layer does not matter), with a thickness corresponding to the real thickness of the pavement. The properties of that top layer should be modified as follows:

  • Switch to Tier 2 and customize the soil type;
  • Modify  the value for air-filled porosity θa according to the type of pavement (Table 10 of the Flemish/Brussels and Walloon version of the Technical Guidance Document can be used as a guide, but you should check the validity of the data for your conditions);
  • Change the value for total porosity θs to 2 times the value of the air-filled porosity θa;
  • Change the value for water-filled porosity θw to 0.

The remaining soil properties do not need to be changed and certainly does not have to be set to 0 (which should lead to erroneous results).

On the Indoor air tab, make sure that the paved top layer is not involved in the sub-building soil profile (i.e., the depth of the floor of the concrete slab, the crawl space or the basement floor below the soil surface should be equal to or bigger than the thickness of the paved top layer).

On the Concentrations tab, fill in a concentration of 0 mg/kg dm for the paved top layer.

You should not use the above approach if the pavement is of bad quality (i.e., with cracks and holes), if the contaminated area is only partially paved, or if the pavement is of an open type (e.g., to allow rainwater infiltration).

 

last modified on 04/12/2017 - 12:00

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