COMPARISON OF FLOW RATES THROUGH POROUS PARKING MATERIALS

Traditional parking lot materials such as concrete and asphalt prevent infiltration of water into the subsurface, which leads to surface runoff during storm events. These lots interfere with groundwater recharge, and often transport parking lot contaminants directly into surface drainage systems such as creeks and rivers. Since soil can function as a filtration system (Dreelin et al., 2006), installing pervious material not only redirects water back toward its natural path, but also may mitigate pollutant transfer from parking surfaces to surface water systems. This study compares infiltration through various locally (northwest Ohio) available porous paving materials to determine the maximum infiltration rate and the storage capacity of the materials. We used porous asphalt, crushed stone, and recycled plastic shavings in a flow-through column experimental design. We established a uniform standing water level over the paving materials using a packed column and measured flow rates through each column. Additionally we determined the volume of water recovered over time after a known volume was introduced into the column. Results showed an inverse relationship between infiltration capacity and water storage: materials with a high flow-through rate retained the least amount of water. Recycled plastic shavings transmitted water most rapidly and porous asphalt least rapidly, at approximately 15% the transmission rate of the plastic shavings. Dreelin et al., 2006 conclude that porous pavements are an effective means to reduce runoff, which is consistent with the conclusions of this investigation. Freeze-thaw cycles have the capacity to heave parking materials; we additionally determined the effects of such a cycle on each column.