Specifications for materials under permeable pavement surface

Summary of specifications for materials under the pavement surface. For more information, see the footnote (¹). Reference or links to any specific commercial product, process, or service by trade name, trademark, service mark, manufacturer, or otherwise does not constitute or imply endorsement, recommendation, or favoring by the Minnesota Pollution Control Agency.
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 Filter Layer is REQUIRED if using the permeable pavement system to meet permit requirements. 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:

• stone size 1, 2 (see Table 1)
• definitions of aggregates 1
• information on geotextiles 1, 2
• liners 1