Arrange the filter fabric, once the bed is excavated to the final grade. Overlap the fabric of the filter at least 16 inches. It should stretch outside the bed for at least four inches. The surplus fabric is folded over the stone bed unless the porous asphalt layer is built to partially shield it from sediment.

Drainage pipe should be installed, if necessary.


The aggregate for the stone recharge bed should be arranged in such a manner that the filter fabric remains undamaged. Aggregate should be disposed at the edge of the bed and arranged in layers of 8 to 12 inches by applying track equipment. Compact each lift with a single pass of a light steel wheel roller.

The porous asphalt layer is placed in 2- to 4-inch-thick lifts using track pavers, following state or national guidelines for the construction of open-graded asphalt mixes.