A graded stone chip (ASTM No. 9) is used to fill the joints of permeable paver systems. This allows rapid infiltration of water. Over time, leaves, dirt and debris can build up in the joints reducing the permeability of the surface. Keeping the joints unclogged is the key. For small areas, this is done with a stiff broom, leaf blower and/or pressure washer. This type of maintenance is typically performed once every ten years to maintain optimal premeability.