Attenuation for Pervious Surfaces

Skeletank solutions for Attenuation with Pervious Surfacings

Pervious surfacings are preferred, according to The Building Regulations 2000 H3, where it is not possible for impervious surfaces to be ‘freedraining’ i.e. for paths, driveways or other narrow areas of paving to drain to, ‘pervious areas such as grassland’.

The Skeletank range of techniques and modular products allow you to design attenuated SuDS in conjunction with pervious surfacings. These may be fully sealed, or geotextile lined ‘Leaky Tank’ systems.

In some instances it will be possible to use pervious surfacings with unsealed attenuation systems within 5m of building foundations, (although ground conditions should be thoroughly investigated to ensure their suitability for this).

View the fact sheet USING SUDS CLOSE TO BUILDINGS.

 

Pervious Pavement Design Incorporating Skeletank HPDC Units

Skeletank HPDC Units provide designers with an ideal solution for diffusing rainwater into and out of the permeable aggregate layers* below pervious surfacings. Units are fully compliant with the requirements of BS7533-13:2009 Annex B, ‘Typical physical properties of replacement systems (geo-cellular) units.

Units are available in two modular sizes:

SELH02003 – 708 x 708 x 150mm deep, for catchments up to 100m2

SELH02001 – 2124 x 354 x 300mm deep, for catchments up to 250m2

HPDC attenuation system for pervious surface

If ground conditions are suitable then it may be possible to encapsulate the aggregate layers with HydroWMS 300 HD Geotextile forming a ‘leaky tank’ to keep costs to a minimum. However, if a fully sealed system is required then the aggregate layer should be encapsulated by HydroWMS Geomembrane, protected by HydroWMS 300HD Geotextile. If additional hydrocarbon treatment is required then HydroWMS Permafilter® Geotextile can be utilised above the aggregate layers beneath the pervious surfacings.

The aggregate layers beneath a pervious surface provide one level of treatment, which satisfies Section 2 of the optional Water Quality Criteria in Category 4 of The Code for Sustainable Homes and thus gains one additional credit (if required).

*Note: when using this technique a suitable highly voided aggregate – e.g. Aggregate Industries SudsAgg or similar – should be used

Skeletank products shown in this example

SELH02003

SELH03001

SELH03002

SELH05001

SELH05002

SELH05003

 

Note: Specification options for Geotextiles are a choice of either SELH05002 HydroWMS Permatex HD 300 Geotextile or SELH05003 HydroWMS Permafilter Geotextile.

 

 

Pervious Pavement Design Using Skeletank HPDC Units to Supplement Storage Volumes

If the standard permeable aggregate layer beneath your pervious surface is not providing sufficient storage to meet volume requirements (usually due to low permeability of underlying subsoils), but increasing the depth of aggregate to provide more storage is a problem (e.g. because of high water tables, or other factors restricting excavation) then the larger of the two Skeletank HPDC Units (SELH02001) can be utilised to increase storage volumes, within the aggregate layer, without increasing excavation depths.

Attenuation With Pervious Surface using HPDC SELH-02001

If ground conditions are suitable then it may be possible to encapsulate the aggregate layers with HydroWMS 300 HD Geotextile forming a ‘leaky tank’ to keep costs to a minimum. However, if a fully sealed system is required then the aggregate layer should be encapsulated by HydroWMS Geomembrane, protected by HydroWMS 300HD Geotextile. If additional hydrocarbon treatment is required then HydroWMS Permafilter® Geotextile can be utilised above the aggregate layers beneath the pervious surfacings.

The aggregate layers beneath a pervious surface provide one level of treatment, which satisfies Section 2 of the optional Water Quality Criteria in Category 4 of The Code for Sustainable Homes and thus gains one additional credit (if required).

*Note: when using this technique a suitable highly voided aggregate – e.g. Aggregate Industries SudsAgg or similar – should be used.

 

Skeletank products shown in this example

SELH-02001-HDPC

SELH02001

SELH03001

SELH03002

SELH05001

SELH05002

 

Note: Specification options for Geotextiles are a choice of either SELH05002 HydroWMS Permatex HD 300 Geotextile or SELH05003 HydroWMS Permafilter Geotextile.