a vertically draining , particulate confinement structure may prevent side to side migration of particulate materials and may provide a way to ensure a consistent fill depth of the particulate materials . the particulate materials may include rubber granules . the vertical draining feature of the system may prevent water from accumulating on the turf surface by providing adequate vertical drainage . the vertical draining feature may be attributed to the combination of the turf surface with a confinement structure and the particulate materials that support this turf surface . the confinement structure and particulate materials also inhibit underlayment migration of the turf surface .