Summary of specifications for materials under the pavement surface.
Link to this table

Material
Specification
Notes
Bedding/choker layer
  • Pervious concrete: None
  • Porous asphalt: 1inch of AASHTO No. 57 stone
  • PICP: 2 inches of AASHTO No. 8 stone (MnDOT 3127FA-3)
Washed free of fines
Reservoir Layer
  • Pervious concrete: AASHTO No. 57 stone or per hydraulic design
  • Porous asphalt:AASHTO No. 2, 3, or 5 stone
  • PICP: 4 inches of AASHTO No. 57 base and AASHTO No.2, 3 or 4 stone subbase
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).