Filter Strips - Technical Information

Polypipe GI solution   

Filter strips alone can make a valuable contribution to Green Infrastructure creating conveyance and storage at source. Conventional SuDS designs can be enhanced by the use of Polypipe Geotextiles.

Hydrocarbon concentrations within surface water infiltrating through the Permafilter is limited to a maximum 5 parts per million (ppm) [5mg/l].*

It should be further noted that Permafilter encourages the formation of a biofilm, that actively biodegrades retained hydrocarbons.

*Based on an oil load of 0.6 l/m² (600ml/m²) 

Filter strips may be designed to encourage infiltration into the underlying soils through the use of shallow gradients.
 

While significant infiltration of surface water would not normally be considered possible for this type of SuDS element, filter strips can potentially make a significant contribution to interception storage.
 

Design water flow velocities should typically be restricted below 1.5m/s to prevent erosion, however, it should be noted that lower velocities would be required to achieve efficient levels of water treatment.
 

Additional water storage can be created within the filler media by substitution of some of the material in the granular filled silt trap/flow spreader with Ridgidrain or Polystorm.