Dimensioning using a spreadsheet


Dimensioning using a spreadsheet


EXPO-NET has developed an Excel spreadsheet for calculating the dimensioning of BIO-BLOK® rain water drywells. The spreadsheet can calculate the use of BIO-BLOK® elements for five different types of soil – coarse sand, fine sand, silt, sandy clay and silty clay.

The spreadsheet is available for download by clicking on the link below. It is a good idea to save the spreadsheet before use.

Before you open the spreadsheet for the first time you must ensure that the security settings in Excel are correct. The Security Level must be set at “Medium”. This can be done by opening the Excel application, then go to “Tools” in the main menu, select “Options” and go to the “Security” tab – click on the “Macro Security” button and under the “Security Level” tab, select “Medium”.

The spreadsheet can now be opened. Remember that you must open the spreadsheet “With Macros” in order to activate the formulae that perform the calculations.

To download the spreadsheet, click on the icon below:

The use of the spreadsheet is at your own risk.

Drainage table for BIO-BLOK® rainwater drywells: 

 Drainage area: 100 m2
 BIO-BLOK® drywell
 (width x height)
8 tubes’ width
0.54 x 0.55m
4 tubes’ width
0.27 x 0.55m
2 tubes’ width
0.135 x 0.55m
 Soil type / K value Length of drywell / use of whole blocks
 Coarse sand / 10-3 m/sec. 1.08m / 2 pcs. 1.08m / 1 pcs. 2.16m / 1 pcs.
 Fine sand / 10-4 m/sec. 3.24m / 6 pcs. 4.32m / 4 pcs. 6.48m / 3 pcs.
 Fine soil (silt) / 10-5 m/sec. 6.48m / 12 pcs.  10.80m / 10 pcs. 17.28m / 8 pcs.
 Sandy clay / 10-6 m/sec.  10.48m / 20 pcs.  18.36m / 17 pcs. 32.4m / 15 pcs.
 Silty clay / 10-7 m/sec.  16.20m / 30 pcs.  30.24m / 28 pcs.  58.32m / 27 pcs.

The above calculations are in accordance with Publication no 25 of the Danish Wastewater Committee.
The values of 10-7 m/sec. are estimated by extending the current charts.
The drywells are dimensioned on the basis of an expected overload of maximum once per year (T = 1 year).