Specifications for materials under permeable pavement surface
Summary of specifications for materials under the pavement surface.1
Link to this table
| Bedding/choker layer |
|
Washed free of fines |
| Reservoir Layer |
|
Stone layer thickness based on the pavement structural and hydraulic requirements. Stonewashed and free of fines. Recommended minimum void ratio = 0.4. |
| Underdrain (optional) | Use 4 to 6 inch diameter perforated PVC (AASHTO M-252) pipe or corrugated polyethylene pipe. Perforated pipe installed for the full length of the permeable pavement cell, and non-perforated pipe, as needed,connected to storm drainage system. | |
| Filter Layer (optional) | Sand filter layeris separated from base above and native soils with geotextile. Sand layer typically ASTM C33 gradation, 6 to 12 inches thick. | The sand layer may require a choker layer on surface to provide transition to base layerstone. |
| Geotextile(optional) | Comply with AASHTO M-288 Standard Specification for Geotextile Specification for Highway Applications, drainage and separation applications, Class I or II. Porous asphalt industry recommends non-woven geotextile. | |
| Impermeable Liner | Use a minimum 30mil PVC liner covered by 12 ounce/square yard non-woven geotextile. EPDM and HDPE liner material is also acceptable. | |
| Observation Well | Use a perforated 4 to 6 inch vertical PVC pipe (AASHTO M-252) with a lockable cap, installedflush with the surface (or under pavers). | |
1for additional information on materials referenced in this table (e.g. stone dimensions), see the following links: