Rainfall Calculations

Rainfall Incidents for Perth (Ref. http://www.BOM.gov.au):

 

Perth rainfall

Most councils choose the risk of a 1 in 20 year storm for the 5 minute duration (highest volume flow rate once every 20 years).

Perth Sand Infiltration Rate = 0.1 m3/m2 per second, = 6L/min per m2

This means that if the sub base is acceptable as Class A, and for residential traffic or light traffic eg carparks:

The sand alone will allow infiltration of 30 L per 5 minute storm, which is well above the required rate.

Therefore the Fast Flow pavers can be laid directly onto compacted Bassendean sand and meet the stormwater requirements.

Is the Paver Permeability Sufficient?
From the above table, the Fast Flow Pavers TM must pass a minimum of 12.5 litres per m2 over 5 minutes.
The maximum flow rate through Fast Flow Pavers is >10 L litres per m2 in 1 minute, or over 50L in 5 minutes.
Therefore this 20 year storm event is approximately one quarter of the flow rate through the pavers.

See Certified Installation Drawings for this information in easy format.