Sustainable Urban Drainage Systems (SUDS)
Sustainable Urban Drainage Systems manage surface water drainage by incorporating drainage methods, such as pervious surfaces, that can handle both water quantity and quality issues. Pervious surfaces can be either porous or permeable, the distinction between the two being: -
- A Porous surface allows water to infiltrate across the entire surface.
- A Permeable surface is formed of material impervious to water but allows infiltration through a pattern of voids and channels which handle surface run-off.
Permeable Pavements
Permeable Pavements consist of a surface course of paving units laid with wide joints, voids or openings that allow water to pass through the pavement construction into an open graded sub-base designed to store the surface water run-off. Permeable Pavements also allow pollutants to be dealt with and storm water to be released at a controlled rate into the surrounding ground.
For permeable block paving formed from concrete, clay or stone pavers, the key to a successful Sustainable Urban Drainage System is to use "No Fines" sub-bases with a high proportion of void spaces within them. These void spaces give the sub-base the ability to store surface water run-off.
The sub-base should be a hard, angular material of either primary or secondary aggregate origin. This angularity gives the sub-base a high degree of interlock and stability, post compaction, allowing it to bear the weight of the overlying pavement layers. Heavily trafficked areas and pavements constructed over poor ground can incorporate layers of "hydraulically bound material" (HBM's) to improve their load bearing capacity and performance. Day Aggregates can supply both sub-base materials and design mix HBM'S for incorporation into Permeable Pavements.
Dependent upon the use of the surface and the surface paving material, the underlying construction will consist of layers of granular crushed rock of varying depth in relation to the sub-base thickness required to achieve the specified storage and loading factors.
Typical Permeable Pavement Design from BS7533-13:2009.
Laying Course
This is the layer of material on which the paving units are bedded, facilitating the free passage of water through to the underlying sub-base layers. Materials can be a 2/6mm clean stone or a 2/6mm clean hard grit or Sharp Washed Sand - all available from Day Aggregates. A 3mm grit should be used to infill the gaps between the pavers, again available from Day Aggregates.
Typical Grading for a Permeable Pavement Laying course.
BS Sieve Size (BS EN 993-1) mm |
Percentage Passing |
14 |
100 |
10 |
98-100 |
6.3 |
80-99 |
2.0 |
0-20 |
1.0 |
0-5 |
Sub-Base Course
This consists of one or more layers of open graded angular material placed above the natural subgrade such as 10/63mm, 4/20mm and 2/6mm clean stone - all available from Day Aggregates. The pavement design will incorporate the above materials in varying amounts depending on the pavement design specification.
Sub-base Aggregates: Typical Grading Analyses.
Sieve Size mm |
Percentage Passing |
||
Coarse Aggregates 10/63mm |
Coarse Aggregates 4/40mm |
Coarse Aggregates 4/20mm |
|
80mm |
100 |
100 |
|
63mm |
|
98-100 |
|
40mm |
70 |
90-99 |
100 |
31.5mm |
|
|
98-100 |
20mm |
22 |
27-70 |
90-99 |
14mm |
|
|
|
10mm |
2 |
|
25-70 |
6.3mm |
|
|
|
4mm |
|
0-15 |
0-15 |
2mm |
|
0-5 |
0-5 |
1mm |
|
|
|
0.500mm |
|
|
|
0.063mm |
|
|
|
BS7533-13:2009 - available from the British Standards Institute - provides design advice on Pavements constructed with clay, natural stone or concrete pavers including advice on the materials required in the Laying and Sub- Base Courses.
- For more information contact our sales office on 0845 0654 655 or email us.
